Country：Japan

Award type：Award from Japanese society, conference, symposium, etc. 

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acscatal.9b04491

Web of Science

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/d1ob00126d

PubMed

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/d0ob01862g

Web of Science

PubMed

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3987/COM-20-S(K)32

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/d0cc04821f

Web of Science

PubMed

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/ajoc.202000067

Web of Science

Publishing type：Research paper (scientific journal)   Publisher：公益社団法人 日本化学会  

<p>The effectiveness of a catalytic amount of bromide ions for significantly accelerating the palladium-catalyzed allylation of carbonyl compounds with allylic carbonates is reported. In particular, the utilization of an ammonium–phosphine hybrid ligand bearing a bromide ion is uniquely effective for promoting allylation under mild, base-free conditions, thus obviating the need to use polar solvents and external strong Brønsted bases.</p>

DOI： 10.1246/cl.200264

CiNii Article

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/jacs.9b09556

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s41061-019-0256-1

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/s41467-019-10641-y

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c9qo00197b

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/cl.190197

Language：English   Publishing type：Research paper (scientific journal)  

<p>Strigolactones have diverse functions as plant hormones and as ecological signals to communicate with soil microbes. Strigolactones are also exploited by parasitic plants, including noxious parasitic weeds called <i>Striga hermonthica</i>, as germination cues that enable efficient parasitism to their host plants. Recent understanding for the mechanism of strigolactone perception by α/β-hydrolase receptors has provided opportunities to dissect the diverse functions with synthetic strigolactones. Here, we introduce the design principle of the synthetic strigolactones, which relies on a hybrid of two functions encoded in the two substructures, ABC-ring and D-ring. The principle discussed here has been applied to develop a <i>Striga</i>-selective suicide germination stimulant acting at femtomolar-range.</p>

DOI： 10.18978/jscrp.54.1_49

CiNii Article

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1126/science.aau5445

Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/bcsj.20180098

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/jacs.7b12949

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/anie.201800057

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/cl.180031

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/jacs.7b13433

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5059/yukigoseikyokaishi.76.565

CiNii Article

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C7CC07122A

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c7sc01524k

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C7SC01700F

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C7CC02502E

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C7CC01715D

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acscatal.7b00265

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/ncomms14793

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/bcsj.20170040

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1055/s-0036-1558958

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3987/COM-16-13642

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.joc.6b02572

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3762/bjoc.12.199

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/cl.160158

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1055/s-0035-1561403

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/bcsj.20160053

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.joc.6b00445

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/jacs.5b09329

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C4CC10261D

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/anie.201503928

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/cl.150581

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C5SC02170G

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/NCHEM.1796

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/cs501369z

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.tet.2013.12.086

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3987/COM-13-S(S)121

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C3CC49338E

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1055/s-0033-1340818

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C3CC49477B

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C4SC01032A

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C4CC06081D

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/asia.201402943

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A catalyst-controlled, geometrically divergent asymmetric Michael addition of azlactones to methyl propiolate has been achieved under the catalysis of P-spiro chiral triaminoiminophosphoranes. An uncommon O-protonation of the intermediary allenic enolate is proposed to rationalize geometric control and its validity is proven by the development of highly Z- and enantioselective Michael addition of azlactones to cyanoacetylene with broad substrate scope.

DOI： 10.1039/C2SC22027J

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ja406999p

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ja411647x

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ja403491j

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A highly enantioselective allylation of benzofuran-2(3H)-ones is achieved under Pd catalysis by taking full advantage of the structural modularity of ion-paired chiral ligands.

DOI： 10.1021/ja312125a

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A vinylog of Michael addition (1,6-addition) of azlactones to δ-substituted dienyl N-acylpyrroles has been developed with virtually complete 1,6-, diastereo-, and enantioselectivities by means of chiral P-spiro triaminoiminophosphorane as a catalyst. This system has been successfully extended to an unprecedented bis-vinylog of Michael addition (1,8-addition) of azlactones to ζ-substituted trienyl N-acylpyrroles with high levels of regio- and stereocontrol.

DOI： 10.1021/ja310209g

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A highly enantioselective sulfa-Michael addition to aromatic and aliphatic nitroolefins is achieved under the synergistic catalysis of chiral, ionic Brønsted acid homo-1b·HBArF and 2,6-lutidine. The potential utility of this new method is clearly demonstrated by its application to the syntheses of a novel, optically active taurine derivative and β-sultam.

DOI： 10.1039/C2SC20698F

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Vinylogous nitronate was successfully generated from β,β-disubstituted nitroolefins for achieving a highly regio-, diastereo-, and enantioselective aza Henry reaction under the influence of chiral ammonium betaine of type 1 as an organic-base catalyst. The present approach greatly expands the synthetic utility of nitroolefins in the development of carbon-carbon bond-forming reactions.

DOI： 10.1002/chem.201201259

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

An efficient asymmetric Mannich-type reaction of α-cyano α-sulfonyl carbanions has been achieved by exploiting the structural modularity and anion-recognition ability of chiral 1,2,3-triazolium ions. This protocol has proven to be applicable to a variety of N-Boc imines and cyanosulfones, affording β-amino α-cyanosulfones in excellent yields with high stereoselectivities.

DOI： 10.1039/C2CC32398B

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Catalytic asymmetric chloride and bromide ring openings of meso aziridines with trimethylsilyl halides have been developed using modular chiral 1,2,3-triazolium chlorides as catalysts. Control experiments suggest the reaction pathway involving hypervalent silicate ions as reactive intermediates. The application of this system to the efficient kinetic resolution of terminal aziridines is also reported.

DOI： 10.1021/ja3028668

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A new strategy for developing stereoselective bond-forming reactions is introduced; it takes advantage of the ionic nucleophilic catalysis of chiral ammonium betaines to utilize vinylic esters simultaneously as the enolate precursor and the acylating agent for coupling with electrophiles. Its synthetic utility is clearly demonstrated by the realization of a highly diastereo- and enantioselective aldol reaction from oxindole-derived vinylic carbonates.

DOI： 10.1021/ja3022939

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Pass the P: Catalytic direct aldol addition of α-hydroxy trialkyl phosphonacetates to aldehydes affords α-hydroxy-β-phosphonyloxy ester products. The fully substituted glycolate enolate intermediate is generated in situ under mild conditions by a [1,2] phosphonate-phosphate rearrangement. High enantioselectivity and dramatic enhancement of reaction diastereocontrol is realized by the application of chiral iminophosphorane catalysts.

DOI： 10.1002/anie.201200559

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Conventional chiral ligands rely on the use of a covalently constructed, single chiral molecule embedded with coordinative functional groups. Here, we report a new strategy for the design of a chiral ligand for asymmetric transition-metal catalysis; our approach is based on the development of an achiral cationic ammonium-phosphine hybrid ligand paired with a chiral binaphtholate anion. This ion-paired chiral ligand imparts a remarkable stereocontrolling ability to its palladium complex, which catalyses a highly enantioselective allylic alkylation of α-nitrocarboxylates. By exploiting the possible combinations of the achiral onium entities with suitable coordinative functionalities and readily available chiral acids, this approach should contribute to the development of a broad range of metal-catalysed, stereoselective chemical transformations.

DOI： 10.1038/nchem.1311

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Highly enantioselective conjugate addition of 2-unsubstituted azlactone 3 to various nitroolefins 4 was accomplished by the selective utilization of supramolecularly assembled, chiral tetraaminophosphonium aryloxide-arylhydroxide 1a·[2a]2 as a requisite catalyst. The key to this achievement is the polarity dependence of the molecular associations of type 1·[2]n and the crucial role of the proximal arylhydroxide 2 as a proton donor. The present method offers an attractive route to various optically active amino carbonyl compounds including β2-amino acids.

DOI： 10.1039/C1SC00678A

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Enantioselective aza-Michael addition to conjugated nitroenynes has been developed. P-Spiro heterochiral arylaminophosphonium barfate 1bBArF effectively catalyzes the reaction, and the corresponding conjugate adducts, β-amino homopropargylic nitro compounds, are obtained in good chemical yields with high enantio­selectivities.

DOI： 10.1055/s-0030-1260541

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/anie.201007752

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A C1-symmetric chiral ammonium betaine has been developed, and its intramolecular ion-pairing structure in solid state and its catalytic performance to achieve the highly stereoselective Mannich-type reaction of 2-alkoxythiazol-5(4H)-ones are revealed.

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：Japanese  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Chiral diaminodioxaphosphonium salts have been developed and their unique abilities as a chiral proton have been revealed through the establishment of a highly enantioselective protonation of α-amino acid-derived ketene disilyl acetals.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Triple for all: Various optically active anti-β-nitro propargylic alcohols are synthesized by the catalytic stereoselective addition of nitroalkanes to ynals (the direct Henry reaction of ynals). The utilization of the rich chemistry of carbon–carbon triple bond allows rapid access to three natural products.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Catalyst debut: The chiral ammonium betaine 1 has been successfully applied to the asymmetric Steglich rearrangement as an ionic nucleophilic catalyst. The catalyzed reaction results in record levels of product enantioselectivity, and has a broad substrate scope. M.S.=molecular sieves, Troc=2,2,2-trichloroethoxycarbonyl.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Catalytic, highly enantioselective hydrophosphonylation of ynones has been achieved by exploiting the characteristic features of in situ generated chiral tetraaminophosphonium phosphite.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The catalytic performance of C1-symmetric chiral ammonium betaines in the enantioselective direct Mannich-type reaction of α-nitrocarboxylates with N-Boc imines has been investigated. The most effective catalyst structure has been identified; this provides a reliable synthetic route to a variety of enantiomerically enriched α-tetrasubstituted α,β-diamino acid derivatives.

Language：English   Publishing type：Research paper (scientific journal)  

Highly enantioselective phase-transfer-catalyzed alkylation of tert-butyl 2-benzoyloxy-3-oxobutanoate was realized by the use of an N-spiro chiral quaternary ammonium salt, as a complementary approach to the asymmetric hydroxylation of -alkyl--keto esters. The synthetic utility of the alkylated compounds is highlighted by the diastereoselective reduction and alkylation of the remaining ketone moiety to give various enantiomerically enriched congested 2,3-dihydroxycarboxylic acid esters.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The stereoselective direct Henry reaction of pyruvates mediated by chiral P-spiro tetraaminophosphonium salts is described. High levels of diastereo- and enantioselectivities have been achieved by the use of L-valine-derived (P,S)-2e bearing para-chlorophenyl groups as a precatalyst.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Research to develop structurally discrete, chiral supramolecular catalysts for asymmetric organic transformations has met with limited success. Here, we report that a chiral tetraaminophosphonium cation, two phenols, and a phenoxide anion appear to self-assemble into a catalytically active supramolecular architecture through intermolecular hydrogen bonding. The structure of the resulting molecular assembly was determined in the solid state by means of x-ray diffraction analysis. Furthermore, in solution the complex promotes a highly stereoselective conjugate addition of acyl anion equivalents to {alpha},β-unsaturated ester surrogates with a broad substrate scope. All structural components of the catalyst cooperatively participate in the stereocontrolling event.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Heterochiral [7.7]-P-spirocyclic arylaminophosphonium barfates have been designed as a novel charged, cationic Brønsted acid catalyst, and their catalytic and stereocontrolling abilities have been clearly demonstrated in the development of the unprecedented, highly enantioselective conjugate addition of arylamines to nitroolefins. This study uncovers a new function of chiral tetraaminophosphonium cations and its potential synthetic utility, thereby providing a new avenue to the molecular design of chiral charged Brønsted acid catalysts and their applications.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Highly enantioselective alkylation of azlactones derived from α-amino acids has been achieved under solid-liquid phase-transfer conditions using P-spiro chiral tetraaminophosphonium salt as a catalyst. The resulting alkylated azlactones can be readily converted into the corresponding α,α-disubstituted α-amino acids through simple acidic hydrolysis.

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The generation of chiral tetraaminophosphonium dialkyl phosphite has been detected by low-temperature NMR analysis, and its synthetic potential as a remarkably reactive P-nucleophile has been successfully demonstrated by its application to the establishment of highly efficient and enantioselective hydrophosphonylation of various aldehydes. A systematic evaluation of the organic-base-dependent generation of the requisite ion pair and its reactivity and selectivity as a P-nucleophile reveals that the structure of the cationic conjugate acid of the base is a key element both for substantial generation of phosphite anions with prominent nucleophilicity and for rigorous stereocontrol. This study provides not only experimental demonstration of the importance of the phosphite tautomer in the PC bond formation process but also a general yet valuable framework for the molecular design of even superior chiral organic base catalysts.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Dual-purpose activation: Peptide C-terminal azlactones I undergo stereoselective alkylation with high efficiency by the use of a newly devised chiral tetraaminophosphonium salt as a phase-transfer catalyst (PTC), and the alkylated azlactone products II can be employed directly for peptide ligation (see scheme, LG=leaving group). In this way, a wide range of chiral quaternary -amino acid residues can be incorporated at specific sites of a peptide strand.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Regiodivergent 1,2-rearrangement of a-siloxy aldehydes bearing a-aryl and a-alkyl substituents into a-siloxy ketones has been realized by using different Al Lewis acid catalyst/solvent systems. The scope of this unprecedented protocol has been investigated with various substrates, clearly demonstrating its utility for the selective synthesis of two structural isomers from one substrate. Controlled experiments proved that the regiodivergency resulted from the switch of the migrating group.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A chiral ammonium betaine, an intramolecular ion-pairing quaternary ammonium aryloxide, has been designed and its vast potential as an enantioselective organic base catalyst has been successfully demonstrated in the highly enantioselective direct Mannich-type reaction of α-substituted α-nitrocarboxylates with various N-Boc imines. The present study provides a conceptually new approach toward the design of bifunctional, chiral quaternary ammonium salts and their utilizations as a homogeneous organic molecular catalyst.

Language：English   Publishing type：Research paper (scientific journal)  

Regiodivergent 1,2-rearrangement of alpha-siloxy aldehydes bearing alpha-aryl and alpha-alkyl substituents into alpha-siloxy ketones has been realized by using different Al Lewis acid catalyst/solvent systems. The scope of this unprecedented protocol has been investigated with various substrates, clearly demonstrating its utility for the selective synthesis of two structural isomers from one substrate.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The cooperative asymmetric catalysis of chiral tetraaminophosphonium carboxylate (P,S)-1·OCOR has been established, and its synthetic utility has been successfully demonstrated by application to the highly enantioselective direct Mannich-type reaction of azlactones with N-sulfonyl imines. The present study stimulates the cultivation of the potential of the chiral quaternary onium salt catalysis by the structural modification of organic anion.

Authorship：Lead author   Language：Japanese  

Language：English  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

A chiral tetraaminophosphonium salts possessing the phosphorus-centered [5.5]-spirocyclic core have been designed and synthesized in a single step from L-valine-derived diamine. The three-dimensional molecular structure was successfully verified by the single-crystal X-ray diffraction analysis, which also identified a secondary interaction between the phosphonium cation and chloride ion via double hydrogen-bonding. The potential of this novel onium salt as a chiral organic molecular catalyst has been demonstrated in an application to asymmetric direct Henry reaction.

Language：English  

Language：English  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Highly efficient, catalytic enantioselective synthesis of N-arylsulfonyl α-amino nitriles from the corresponding α-amido sulfones has been achieved under toluene–aqueous potassium cyanide biphasic conditions using chiral quaternary ammonium iodide (R,R,R)-1 as an effective phase-transfer catalyst. This Strecker synthesis involving the in situ generation of the reactive N-sulfonyl imines is advantageous for the cyanation of the substrates having primary and secondary alkyl substituents.

Language：English   Publishing type：Research paper (scientific journal)  

Phase-transfer-catalyzed alkylation of glycinate Schiff base with racemic secondary alkyl halides proceeded with excellent levels of syn- and enantioselectivities under the influence of chiral quaternary ammonium bromide 1d and 18-crown-6. The alkylation product can be selectively converted to the corresponding anti isomer, allowing the preparation of all the stereoisomers of -alkyl--amino acid derivatives, an extremely valuable chiral building block.

Language：English   Publishing type：Research paper (scientific journal)  

A catalytic asymmetric rearrangement of alpha,alpha-dialkyl-alpha-siloxy aldehydes has been developed based on the design of a stereochemically defined, axially chiral organoaluminum Lewis acid. The scope of this unprecedented stereoselective rearrangement has been investigated with representative substrates, in which impressive kinetic resolution of racemic, alpha,alpha-disubstituted alpha-siloxy aldehydes has also been achieved. These results clearly demonstrate the utility of the present approach for the catalytic enantioselective synthesis of various acyloins and tertiary alpha-hydroxy aldehydes not readily accessible by the previously known asymmetric methodologies.

Language：English   Publishing type：Research paper (scientific journal)  

An efficient catalysis of new chiral quaternary ammonium bifluoride in combination with silyl nitronates has been successfully utilized for achieving the highly diastereo- and enantioselective formal conjugate addition of nitroalkanes to nitroalkenes. This unique catalytic asymmetric protocol provides a reliable access to various 1,3-dinitro compounds bearing stereochemically defined two consecutive stereocenters, which serve as a versatile chiral building block in organic synthesis.

Language：English   Publishing type：Research paper (scientific journal)  

The enantioselective construction of all-carbon quaternary stereocenters on -acyl--butyrolactones has been achieved by the N-spiro chiral quaternary ammonium bromide 1-catalyzed alkylation under mild phase-transfer conditions. The resulting -alkylated keto lactones serve as valuable chiral building blocks in organic synthesis as clearly demonstrated by the facile conversion to optically active ,-dialkyl--amino acid derivatives via Schmidt rearrangement.

Language：English   Publishing type：Research paper (scientific journal)  

Catalytic, highly enantioselective alkylation of 3,5-diaryloxazoline-2,4-diones has been accomplished under mild phase-transfer conditions using designer chiral quaternary ammonium bromide as catalyst. This catalytic asymmetric glycolate alkylation procedure establishes chiral quaternary carbon centers, and provides a practical access to various optically active tertiary alpha-hydroxy-alpha-arylcarboxylic acid derivatives.

Language：English   Publishing type：Research paper (scientific journal)  

The selective monoalkylation of glycine tert-butyl ester aldimine Schiff base 3 has been realized in high chemical yield with excellent enantioselectivity under mild liquid–liquid phase-transfer conditions by the use of binaphthyl-derived chiral quaternary ammonium bromides 7 and 8 as catalysts. This achievement demonstrates that 3 can be used as a cost-effective substrate for the preparation of optically active α-alkyl-α-amino acid derivatives by chiral phase-transfer catalysis.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

The phase-transfer-catalyzed, highly enantioselective cyanation of aldimines using aqueous KCN has been realized based on the molecular design of chiral quaternary ammonium iodide bearing a stereochemically defined tetranaphthyl backbone. A wide range of aliphatic aldimines, including those having -tert-alkyl substituents, is tolerated by the present system. This study represents a novel approach for the asymmetric Strecker-type reactions, which utilizes chiral phase-transfer catalysts for practical access to various unusual, optically pure -amino acids.

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Inspired by the considerable difference of catalytic activity and stereocontrolling ability between the conformationally rigid, homo- and heterochiral quaternary ammonium bromides 1, conformationally flexible, N-spiro chiral quaternary ammonium bromides of type 4 have been designed and synthesized. Reliable procedures for the preparation of the appropriately substituted biphenyl subunits have been established by the repeated use of ortho magnesiation–halogenation as a key synthetic tool. The relationship between the structure of achiral biphenyl moiety and the reactivity and selectivity of 4 has been evaluated in the asymmetric alkylation of glycinate Schiff base 2 under typical phase-transfer conditions, leading to the identification of 4l as an optimal catalyst structure to exhibit an excellent enantiocontrol in the reactions with various alkyl halides. The molecular structure of 4l was determined by X-ray crystallographic analysis and its unique behavior in solution was examined by a variable-temperature 1H NMR study. These investigations uncovered that the observed high chiral efficiency originated from the efficient asymmetric phase-transfer catalysis of homochiral-4l, which rapidly equilibrated with heterochiral-4l of low catalytic activity and stereoselectivity.

Language：English   Publishing type：Research paper (scientific journal)  

Highly enantioselective alkylation of protected glycine diphenylmethyl (Dpm) amide 1 and Weinreb amide 10 has been realized under phase-transfer conditions by the successful utilization of designer chiral quaternary ammonium salts of type 4 as catalyst. Particularly, remarkable reactivity of the chiral ammonium enolate derived from 1b and 4c allowed the reaction with less reactive simple secondary alkyl halides with high efficiency and enantioselectivity. An additional unique feature of this chiral ammonium enolate is its ability to recognize the chirality of -branched primary alkyl halides, which provides impressive levels of kinetic resolution and double stereodifferentiation during the alkylation, allowing for two - and -stereocenters to be controlled. Combined with the subsequent reduction using LiAlH4 in cyclopentyl methyl ether (CPME), this system offers a facile access to structurally diverse optically active vicinal diamines. Furthermore, the optically active -amino acid Weinreb amide 11 can be efficiently converted to the corresponding amino ketone by a simple treatment with Grignard reagents. In addition, reduction and alkylation of the optically active -amino ketone into both syn and anti -amino alcohols with almost complete relative and absolute stereochemical control have been achieved. With (S,S)- and (R,R)-4 in hand, the present approach renders both enantiomers of -amino amides including Weinreb amides readily available with enormous structural variation and also establishes a general and practical route to vicinal diamines, -amino ketones, and -amino alcohols with the desired stereochemistry.

Language：English   Publishing type：Research paper (scientific journal)  

Highly enantioselective Michael addition of silyl nitronates to cyclic α,β-unsaturated ketones has been accomplished by the utilization of N-spiro C2-symmetric chiral quaternary ammonium bifluoride 1 as an efficient catalyst, offering a new route to the enol silyl ethers of optically active γ-nitro ketones. The synthetic utility of this transformation has been demonstrated by the diastereoselective derivatizations of the optically active enol silyl ethers to the corresponding α-substituted cyclic ketones having three consecutive stereochemically defined stereocenters.

Language：English   Publishing type：Research paper (scientific journal)  

Conjugate addition of various prochiral nitroalkanes to cyclic ,-unsaturated ketones was found to be efficiently catalyzed by N-spiro C2-symmetric chiral quaternary ammonium bromide 1b possessing a 3,5-bis(3,4,5-trifluorophenyl)phenyl substituent under solid-liquid phase-transfer conditions to afford the corresponding -nitro ketones in excellent chemical yields with unprecedented levels of diastereo- and enantiocontrol.

Language：English   Publishing type：Research paper (scientific journal)  

Highly enantioselective Michael addition of diethyl malonate to chalcone derivatives has been achieved under mild phase-transfer conditions by the successful utilization of N-spiro C2-symmetric chiral quaternary ammonium bromide 1 as a catalyst, which possesses diarylhydroxymethyl functionalities as a recognition site for the prochiral electrophile. This simple asymmetric Michael addition process was found to be quite effective for various chalcone derivatives, including those with heteroaromatic substituents.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Practical asymmetric synthesis of functionalized aza-cyclic -amino acid derivatives possessing quaternary stereocenters has been achieved by the phase-transfer-catalyzed alkylation of 2 or 3 using chiral quaternary ammonium bromide 1 as catalyst. Subsequent reduction and alkylation of the 3-keto carbonyl moiety of 4 proceeded with complete diastereochemical control to afford the corresponding -hydroxy aza-cyclic -amino acid derivatives having stereochemically defined consecutive quaternary carbon centers.

Language：English   Publishing type：Research paper (scientific journal)  

The asymmetric phase-transfer catalytic alkylation of peptides has been achieved by the use of designed C2-symmetric chiral quaternary ammonium bromide 1 as catalyst. Excellent stereoselectivities were uniformly observed in the alkylation with a variety of alkyl halides and the efficiency of the transmission of stereochemical information was not affected by the side-chain structure of the preexisting amino acid residues. This method also enables an asymmetric construction of noncoded ,-dialkyl--amino acid residues at the peptide terminal. Since this chirality can be efficiently transferred to the adjacent amino acid moiety, our approach provides a general procedure not only for the highly stereoselective terminal functionalization of peptides but also for the sequential asymmetric construction of unnatural oligopeptides, which should play a vital role in the peptide-based drug discovery process.

Language：English   Publishing type：Research paper (scientific journal)  

A series of (2,7-disubstituted-1,8-biphenylenedioxy)bis(dimethylaluminum) (2) has been readily prepared in situ by treatment of the requisite 2,7-disubstituted-1,8-biphenylenediol (1) with Me3Al (2 equiv) in CH2Cl2 at room temperature; this primarily relies on the successful establishment of a new synthetic procedure of 1 starting from inexpensive m-anisidine. Evaluation of 2 as a bidentate organoaluminum Lewis acid has been performed by the reduction of ketonic substrates using Bu3SnH as a hydride source in comparison to the conventional monodentate Lewis acid dimethylaluminum 2,6-xylenoxide (11), uncovering the significantly high activation ability of 2 toward carbonyl. Particularly, (2,7-dimethyl-1,8-biphenylenedioxy)bis(dimethylaluminum) (2a) exerted the highest reactivity, which has also been emphasized in the Mukaiyama aldol reaction. The structure of the bidentate Lewis acid 2 was unambiguously determined by single-crystal X-ray diffraction analysis of 2g possessing a bulky 3,5-di-tert-butylphenyl substituent, revealing the rigid dimeric assembly in the solid state. The double electrophilic activation of carbonyl substrate by 2a has been supported by low-temperature 13C NMR analysis as well as theoretical study using the Gaussian 98 program. Moreover, unique stereoselectivity has been observed in the 2a-promoted Mukaiyama Michael addition, and highly chemoselective functionalization of carbonyl compounds in the presence of their acetal counterparts has been realized using 2a. Finally, the effectiveness of 2a for the activation of ether functionality has been demonstrated in the Claisen rearrangement of allyl vinyl ethers.

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A novel carbonyl alkynylation has been accomplished based on utilization of the Meerwein–Ponndorf–Verley (MPV) reaction system. The success of the MPV alkynylation crucially depends on the discovery of the remarkable ligand acceleration effect of 2,2-biphenol. For example, the alkynylation of chloral (2c) with the aluminium alkoxide 6(R = Ph), prepared in situ from Me3Al, 2,2-biphenol and 2-methyl-4-phenyl-3-butyn-2-ol (1a) as an alkynyl source, proceeded smoothly in CH2Cl2 at room temperature to give the desired propargyl alcohol 3ca in almost quantitative yield after 5 h stirring. The characteristic feature of this new transformation involving no metal alkynides can be visualized by the fact that the alkynyl group bearing keto carbonyl was transferred successfully to aldehyde carbonyl without any side reactions on keto carbonyl. Although the use of (S)-1,1-bi-2-naphthol and its simple analogues was found to be unsuitable for inducing asymmetry in this reaction, design of new chiral biphenols bearing a certain flexibility of the biphenyl axis led to satisfactory results in terms of enantioselectivity as well as reactivity.

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γ,γ-Dialkyl-γ-amino-α,β-unsaturated carbonyl compounds were found to undergo selective skeletal rearrangement under the influence of modified organoaluminum Lewis acid to give unsymmetrically substituted pyrroles through the rapid Paal–Knorr type cyclization upon acidic hydrolysis. This new structural reorganization of amino carbonyl compounds triggered by the 1,2-alkyl shift provides a unique entry to the synthesis of pyrroles, an important class of heterocycles with diverse biological activities.

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The aldol coupling of ketene silyl acetal 2 derived from the glycinate Schiff base with aldehydes can be efficiently catalyzed by an in situ generated, chiral quaternary ammonium fluoride of type 1 under mild, neutral conditions, affording the corresponding anti--hydroxy--amino esters predominantly with excellent enantioselectivities.

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Unique relationship between the catalyst structure and regio- and stereoselectivity in the chiral quaternary ammonium bifluoride–catalyzed asymmetric addition of silyl nitronates to α,β-unsaturated aldehydes has been reported.

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Phase-transfer-catalyzed direct Mannich reaction of glycinate Schiff base 3 with -imino ester 4 has been accomplished with high enantioselectivity by the utilization of N-spiro C2-symmetric chiral quaternary ammonium bromide 2 as a catalyst. This methodology enables the catalytic asymmetric synthesis of differentially protected 3-aminoaspartate, a nitrogen analogue of dialkyl tartrate. The product (syn-5) was converted into a precursor (6) of streptolidine lactam.

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Phase-transfer alkylation of the benzophenone Schiff base of glycine methyl or ethyl ester (2) was found to be catalyzed by 3,4,5-F3-C6H2-NAS-Br [(S,S)-1] with high efficiency and excellent enantioselectivity. This procedure allows facile derivatization of the resulting alkylation products to other synthetically useful chiral building blocks.

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A new chiral ammonium bromide possessing diarylmethanol functionality as a substrate recognition site has been designed as a promising, dual-functioning catalyst for the highly enantioselective epoxidation of alpha,beta-unsaturated ketones under mild phase-transfer conditions. A variety of alpha,beta-unsaturated ketones can be epoxidized with rigorous stereochemical control, clearly demonstrating the effectiveness and utility of the present system. Further, a successful single-crystal X-ray diffraction analysis of the catalyst uncovered its distinctive three-dimensional molecular architecture and provided useful information for postulating the transition state.

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Chiral organoaluminum complex 1 efficiently catalyzed the asymmetric hetero-ene reaction of commercially available 2-methoxypropene (2) with aldehydes under mild conditions to give the corresponding β-hydroxymethyl ketones 3 in good to excellent chemical yields with high enantiomeric excesses. The asymmetric catalysis of 1 was further applied to the carbonyl addition of methallylsilanes, where exclusive formation of the optically active allylic silanes 5 was achieved.

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A highly efficient direct asymmetric aldol reaction of a glycinate Schiff base with aldehydes has been achieved under mild organic/aqueous biphasic conditions with excellent stereochemical control, using chiral quaternary ammonium salt 1b as a phase-transfer catalyst. The initially developed reaction conditions, using 2 equiv of aqueous base (1% NaOH (aq)), exhibited inexplicably limited general applicability in terms of aldehyde acceptors. The mechanistic investigation revealed the intervention of an unfavorable yet inevitable retro aldol process involving the chiral catalyst. On the basis of this information, a reliable procedure has been established by use of a catalytic amount of 1% NaOH (aq) and ammonium chloride, which tolerates a wide range of aldehydes to afford the corresponding anti--hydroxy--amino esters almost exclusively in an essentially optically pure form.

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Highly enantioselective conjugate addition of nitroalkanes to alkylidenemalonates has been accomplished for the first time by the utilization of efficient phase-transfer catalysis of N-spiro C2-symmetric chiral quaternary ammonium bromide 1. For instance, simple mixing of nitropropane (2, R1 = Et), diisopropyl benzylidienemalonate (3, R2 = Ph), Cs2CO3 (1 equiv), and (S,S)-1 (1 mol %) in toluene at 0 C for 2.5 h gave rise to the desired conjugate addition product 4 (R1 = Et, R2 = Ph) quantitatively (anti/syn = 86:14) with 97% ee (anti isomer). The applicability of this procedure has been demonstrated with other representative alkylidenemalonates and nitroalkanes. Since 4 can be readily transformed into the corresponding -amino acid hydrochloride 5 without loss of diastereo- and enantioselectivity, the present method provides a new and practical access to various optically active -amino acid derivatives.

Language：English  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Authorship：Lead author   Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (scientific journal)  

Synthesis and X-ray crystallographic characterization of fluorotetraphenylbismuth (1) has been achieved for the first time, revealing that the bismuth center of 1 adopts a distorted trigonal bipyramidal geometry with three ipso carbons at the equatorial sites and one ipso carbon and fluorine atom at the apical sites. Contrary to the previous common understanding of this type of organobismuth(V) compound, 1 was found to be thermally stable, maintaining its amphiphilic property. Hence, 1 can be used as an off-the-shelf reagent in organic synthesis, and its utility has been clearly demonstrated in applications to the efficient -phenylation of ketones and esters. For instance, simple mixing of 1 and 1-trimethylsiloxy-3,4-dihydronaphthalene in THF at -40 C and stirring at room temperature for 10 min gave rise to 2-phenyl-1-tetralone almost quantitatively without formation of the polyphenylated products. In addition to the generality of this method, applicability of our approach to the selective -alkenylation of carbonyl compounds was also demonstrated by the use of fluoro(2-phenylethenyl)tris(p-tolyl)bismuth (2) as a representative reagent. These results imply the vast potential of organobismuth(V) compounds of type 1 and 2 as useful precursors of a wide variety of pentavalent organobismuth compounds based on the utilization of the eminent fluorine-silicon interaction or the inherent basicity of the fluorine atom.

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Designer chiral quaternary ammonium bifluoride 1 has been prepared, and both its catalytic and its chiral efficiency have been clearly demonstrated by achieving the first catalytic asymmetric nitroaldol reaction of silyl nitronate with aldehydes. For instance, the reaction of trimethylsilyl nitronate 2 (R1 = Me) with benzaldehyde (R2 = Ph) in THF in the presence of (S,S)-1 (2 mol %) proceeded smoothly at -78 C, giving the corresponding nitroaldol adduct 3 (R1 = Me, R2 = Ph) in 92% isolated yield (anti/syn = 92:8) with 95% ee (anti isomer). The method was found to be successfully applicable to other aromatic aldehydes and silyl nitronates, and a high level of anti selectivity and enantiomeric excess was constantly observed. This finding should lead to the further development of fluoride ion-catalyzed asymmetric carbon-carbon bond-forming reactions.

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A unique asymmetric skeletal rearrangement of symmetrically ,-disubstituted -amino aldehydes has been accomplished for the first time using a chiral organoaluminum Lewis acid 1. For instance, treatment of (S)-2,2'-bis(trifluoromethanesulfonylamino)-1,1'-binaphthyl with Me3Al (1.0 equiv) in toluene at room temperature for 15 min and at 110 C for an additional 15 min produced (S)-1, and a subsequent reaction with -amino aldehyde 2a (R = CH2Ph) at -78 C for 4 h and at -40 C for 12 h resulted in the smooth rearrangement to the zwitterionic iminium intermediate A, which furnished the -hydroxy ketone 3a (R = CH2Ph) in 93% isolated yield with 95% ee (S) after acidic hydrolysis. This result, together with other representative examples, clearly demonstrates the effectiveness of the present method for the hitherto difficult asymmetric synthesis of acyloins. Furthermore, we found that the treatment of the in situ generated A with DIBAH afforded the corresponding anti amino alcohol exclusively without loss of enantiomeric excess. Our approach casts light on the previously unexplored yet potential utility of -amino aldehydes as synthetic building blocks and also provides a new entry to optically active -hydroxy ketones and 1,2-amino alcohols.

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A series of C2-symmetric chiral quaternary ammonium bromides 10 and 11 have been designed as a new, purely synthetic chiral phase-transfer catalyst, and readily prepared from commercially available optically pure 1,1'-bi-2-naphthol as a basic chiral unit. The details of the synthetic procedures of each requisite chiral binaphthyl subunit have been disclosed, and the structures of the assembled N-spiro chiral quaternary ammonium bromides 11a and 11f were unequivocally determined by single-crystal X-ray diffraction analysis. The reactivity and selectivity of these chiral ammonium bromides as chiral phase-transfer catalysts have been evaluated in the asymmetric alkylation of the benzophenone Schiff base of glycine ester 7 under mild liquid-liquid phase-transfer conditions, and the optimization of the reaction variables (solvent, base, and temperature) has also been conducted. Further, the scope and limitations of this asymmetric alkylation have been thoroughly investigated with a variety of alkyl halides, in which the advantage of the unique N-spiro structure of 11 and dramatic effect of the steric as well as the electronic properties of the aromatic substituents on the 3,3'-position of one binaphthyl moiety have been particularly emphasized. Finally, the potential synthetic utility of the present method for the practical asymmetric synthesis of structurally diverse natural and unnatural -amino acids has been demonstrated by its successful application to the facile asymmetric syntheses of (S)-N-acetylindoline-2-carboxylate, a key intermediate in the synthesis of the ACE inhibitor, and L-Dopa (L-3,4-dihydroxyphenylalanine) ester and its analogue.

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Highly enantioselective Michael addition of silyl nitronates to ,-unsaturated aldehydes has been accomplished by the utilization of designer N-spiro C2-symmetric chiral quaternary ammonium bifluoride 1 as an efficient catalyst, providing direct access to both optically active -nitro aldehydes, a very useful precursor to various complex organic molecules including aminocarbonyls, and their enol silyl ethers, a Mukaiyama donor of potential synthetic utility for further selective transformations. For instance, the reaction of trimethylsilyl nitronate 2 (R1 = Me) with trans-cinnamaldehyde (R2 = Ph, R3 = H) in toluene in the presence of (R,R)-1 (2 mol %) proceeded smoothly at -78 C to give the desired enol silyl ether 3 (R1 = Me, R2 = Ph, R3 = H) in 90% isolated yield (anti/syn = 83:17) with 97% ee (anti isomer), and simple treatment of 3 thus obtained with 1 N HCl in THF at 0 C afforded the corresponding -nitro aldehyde 4 quantitatively without loss of diastereo- and enantioselectivity.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

A new N-spiro chiral quaternary ammonium bromide has been designed and assembled from optically active 4,6-disubstitute&shy;d biphenyl subunits. Its utility as an efficient chiral phase-transfer catalyst has been clearly demonstrated by application to the highly enantioselective alkylation of tert-butyl glycinate benzophenon&shy;e Schiff base.

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Environmentally benign scalable procedures are developed to supply enantiomerically pure (R)-3,5-dihydro-4H-dinaphth[2,1-c:1'2'-e]azepine 1 as its hydrogen oxalate salt in a five-step overall yield of 41%, which consist of the following: (1) bis O-triflation of (R)-1,1'-bi-2-naphthol 8 [(CF3SO2)2O, pyridine, PhMe; quantitative yield]; (2) Kumada's cross-coupling [MeMgI, NiCl2(dppp), tert-BuOMe; 96% yield]; (3) radical bromination [N-bromosuccinimide, 2,2'-azobisisobutyronitrile, cyclohexane; 54% yield]; (4) cyclization [allylamine, Et3N, THF, 86%]; (5) N-deallylation [1,3-dimethylbarbituric acid, Pd(OAc)2, Ph3P, PhMe] followed by crystalline salt formation with oxalic acid (overall 92% yield).

Language：English   Publishing type：Research paper (scientific journal)  

Selective, direct ortho magnesiation of (S)-2,2'-bis(isopropoxycarbonyl)-1,1'-binaphthyl (6) has been achieved under mild conditions, using magnesium bis(2,2,6,6-tetramethylpiperamide) [Mg(TMP)2]. In combination with the subsequent reaction with the appropriate electrophiles, bromine and iodine, this method constitutes a key step in establishing a new and concise synthetic route to a wide variety of N-spiro C2-symmetric chiral quaternary ammonium bromides of type 1.

Language：English   Publishing type：Research paper (scientific journal)  

Isopropoxyaluminum 1,1′-biphenyl-2-oxy-2′-perfluorooctanesulfonamide (3) has been evaluated as an aluminum-based catalyst for the Tishchenko reaction. Compound 3 was found to exert high catalytic activity in the reaction with aliphatic aldehydes and also enabled smooth dimerization of enolizable aldehydes. This advantage was highlighted by the quantitative formation of ethyl acetate from acetaldehyde by the present system.

Language：English  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

Phase-transfer catalysis has been successfully utilized for the Neber rearrangement of simple ketoxime sulfonates. For instance, treatment of (Z)-1a with p-toluenesulfonyl chloride (1.2 equiv), tetrabutylammonium bromide (5 mol %) and MeOH (10 equiv) in toluene-50% KOH aqueous solution (volume ratio = 3:1) at 0 C for 2 h, and subsequent benzoylation followed by acidic hydrolysis afforded the protected -amino ketone 2a in 80% isolated yield. On the basis of this finding, asymmetric Neber rearrangement with ketoxime (Z)-1a was examined under phase-transfer conditions using structurally rigid, C2-symmetric chiral quaternary ammonium bromide 3 as catalyst. The desired 2a was obtained in 80% yield and 51% ee. This represents the first experimental demonstration of the substantial involvement of anion pathway in the Neber rearrangement of simple ketoxime sulfonates. Importantly, the reaction with (E)-1a under otherwise similar conditions afforded racemic 2a in 61% yield. Moreover, enhanced enantioselectivity (63% ee) was observed in the rearrangement of the oxime sulfonate derived from (Z)-1b, and notably, use of mesitylene in place of toluene further increased the enantioselectivity to 70% ee. Our approach provides not only a new mechanistic insight but also an opportunity for extending the full synthetic utility of this classical yet useful rearrangement.

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CSJカレントレビュー「キラル化学：その起源から最新のキラル材料研究まで」八島栄次

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Applicant：長瀬産業株式会社

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Date registered：2005 

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