Faculty Profiles - OOI Takashi

Papers - OOI Takashi

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Importance of Chiral Phase-Transfer Catalysts with Dual Functions in Obtaining High Enantioselectivity in the Michael Reaction of Malonates and Chalcone Derivatives. Reviewed

Ooi, Takashi; Ohara, Daisuke; Fukumoto, Kazuhiro; Maruoka, Keiji

Org. Lett. Vol. 7 page： 3195-3197 2005

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.

Dramatic Rate Enhancement of Asymmetric Phase-Transfer-Catalyzed Alkylations. Reviewed

Shirakawa, Seiji; Yamamoto, Kenichiro; Kitamura, Masanori; Ooi, Takashi; Maruoka, Keiji

Angew. Chem., Int. Ed. Vol. 44 page： 625-628 2005

Asymmetric Synthesis of Functionalized Aza-Cyclic Amino Acids with Quaternary Stereocenters by a Phase-Transfer-Catalyzed Alkylation Strategy. Reviewed

Ooi, Takashi; Miki, Takashi; Maruoka, Keiji

Org. Lett. Vol. 7 page： 191-193 2005

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.

Stereoselective Terminal Functionalization of Small Peptides for Catalytic Asymmetric Synthesis of Unnatural Peptides Reviewed

Maruoka, Keiji; Tayama, Eiji; Ooi, Takashi

Proc. Natl. Acad. Sci. USA Vol. 101 page： 5824-5829 2004

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.

Elucidation and Synthetic Utility of the Double Electrophilic Activation Phenomenon. Reviewed

Ooi, Takashi; Takahashi, Makoto; Yamada, Masao; Tayama, Eiji; Omoto, Kiyoyuki; Maruoka, Keiji

J. Am. Chem. Soc. Vol. 126 page： 1150-1160 2004

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.

Meerwein-Ponndorf-Verley Alkynylation of Aldehydes: Essential Modification of Aluminum Alkoxides for Rate Acceleration and Asymmetric Synthesis. Reviewed

Ooi, Takashi; Miura, Tomoya; Ohmatsu, Kohsuke; Saito, Akira; Maruoka, Keiji

Org. Biomol. Chem. Vol. 2 page： 3312-3319 2004

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

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.

「不斉有機触媒としてのキラル相間移動触媒-アミノ酸合成を中心として」 Invited

大井　貴史, 丸岡　啓二

化学と工業 Vol. 57 page： 711-715 2004

「光学活性ジエン配位子が与える新しい不斉環境」

大井　貴史

page： 134 2004

Asymmetric Organocatalysis of Structurally Well-Defined Chiral Quaternary Ammonium Fluorides. Reviewed

Ooi, Takashi; Maruoka, Keiji

Acc. Chem. Res. Vol. 37 page： 526-533 2004

Organoaluminum-Mediated Selective 1,2-Rearrangement of γ,γ-Disubstituted γ-Amino α,β-Unsaturated Carbonyl Compounds Leading to Unsymmetrically Substituted Pyrroles. Reviewed

Ooi, Takashi; Ohmatsu, Kohsuke; Ishii, Hiroki; Saito, Akira; Maruoka, Keiji

Tetrahedron Lett. Vol. 45 page： 9315-9317 2004

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

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.

Anti-selective Asymmetric Synthesis of β-Hydroxy-α-Amino Acid Esters by the in Situ Generated Chiral Quaternary Ammonium Fluoride-Catalyzed Mukaiyama-Type Aldol Reaction. Reviewed

Ooi, Takashi; Taniguchi, Mika; Doda, Kanae; Maruoka, Keiji

Adv. Synth. Catal. Vol. 326 page： 1073-1076 2004

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

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.

Evaluation of the Relationship Between the Catalyst Structure and Regio- as well as Stereoselectivity in the Chiral Ammonium Bifluoride-Catalyzed Asymmetric Addition of Silyl Nitronates to α,β-Unsaturated Aldehydes. Reviewed

Ooi, Takashi; Morimoto, Kumiko; Doda, Kanae; Maruoka, Keiji

Chem. Lett. Vol. 33 page： 824-825 2004

Catalytic Asymmetric Synthesis of a Nitrogen Analogue of Dialkyl Tartrate by Direct Mannich Reaction under Phase-Transfer Conditions. Reviewed

Ooi, Takashi; Kameda, Minoru; Fujii, Junichi; Maruoka, Keiji

Org. Lett. Vol. 6 page： 2397-2399 2004

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

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.

Highly Enantioselective Alkylation of Glycine Methyl and Ethyl Ester Derivatives under Phase-Transfer Conditions: its Synthetic Advantage. Reviewed

Ooi, Takashi; Uematsu, Yukitaka; Maruoka, Keiji

Tetrahedron Lett. Vol. 45 page： 1675-1678 2004

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

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.

Design of New Chiral Phase-Transfer Catalysts with Dual Functions for Highly Enantioselective Epoxidation of α,β-Unsaturated Ketones. Reviewed

Ooi, Takashi; Ohara, Daisuke; Tamura, Masazumi; Maruoka, Keiji

J. Am. Chem. Soc. Vol. 126 page： 6844-6845 2004

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

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.

Efficient Asymmetric Catalysis of Chiral Organoaluminum Complex for Enantioselective Ene Reactions of Aldehydes. Reviewed

Ooi, Takashi; Ohmatsu, Kohsuke; Uraguchi, Daisuke; Maruoka, Keiji

Tetrahedron Lett. Vol. 45 page： 4481-4484 2004

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

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.

Development of Highly Diastereo- and Enantioselective Direct Asymmetric Aldol Reaction of a Glycinate Schiff Base with Aldehydes Catalyzed by Chiral Quaternary Ammonium Salts. Reviewed

Ooi, Takashi; Kameda, Minoru; Taniguchi, Mika; Maruoka, Keiji

J. Am. Chem. Soc. Vol. 126 page： 9685-9694 2004

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

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.

Highly Enantioselective Conjugate Addition of Nitroalkanes to Alkylidenemalonates Using Efficient Phase-Transfer Catalysis of N-Spiro Chiral Ammonium Bromides. Reviewed

Ooi, Takashi; Fujioka, Shingo; Maruoka, Keiji

J. Am. Chem. Soc. Vol. 126 page： 11790-11791 2004

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

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.

Fluorotetraphenylbismuth: A New Reagent for Efficient Regioselective α-Phenylation of Carbonyl Compounds. Reviewed

Ooi, Takashi; Goto, Ryoji; Maruoka, Keiji

J. Am. Chem. Soc. Vol. 125 page： 10494-10495 2003

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.

Designer Chiral Quaternary Ammonium Bifluorides as an Efficient Catalyst for Asymmetric Nitroaldol Reaction of Silyl Nitronates with Aromatic Aldehydes. Reviewed

Ooi, Takashi; Doda, Kanae; Maruoka, Keiji

J. Am. Chem. Soc. Vol. 125 page： 2054-2055 2003

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

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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Papers - OOI Takashi