Makoto Sako

Asymmetric Brønsted Acid Catalyzed Substitution of Diaryl Methanols with Thiols and Alcohols for the Synthesis of Chiral Thioethers and Ethers.

An enantioselective addition of thiols and alcohols to aza-ortho-quinone methides, starting from diaryl methanols, was developed. The asymmetric additions occur under mild reaction conditions in the presence of chiral phosphoric acids and furnish the corresponding adducts with excellent yields and enantioselectivities.

Efficient Enantioselective Synthesis of Oxahelicenes Using Redox/Acid Cooperative Catalysts

An efficient and enantioselective synthesis of oxa[9]helicenes has been established via vanadium(V)-catalyzed oxidative coupling/intramolecular cyclization of polycyclic phenols. A newly developed vanadium complex cooperatively functions as both a redox and Lewis acid catalyst to promote the present sequential reaction and afford oxa[9]helicenes in good yields with up to 94% ee.

Enantio- and Diastereoselective Betti/aza-Michael Sequence: Single Operated Preparation of Chiral 1,3-Disubstituted Isoindolines

The first enantio- and diastereoselective Betti/intramolecular aza-Michael sequence carried out using a C3-symmetric chiral trisimidazoline organocatalyst is reported. The reaction of phenols and N-tosylimines bearing a Michael acceptor moiety afforded densely functionalized 1,3-disubstituted isoindolines bearing two stereogenic centers as single diastereomers in high yields (≤93%) and excellent enantioselectivities (≤99.9%).

Short Syntheses of 4-Deoxycarbazomycin B, Sorazolon E, and (+)-Sorazolon E2

Short syntheses of 4-deoxycarbazomycin B and sorazolon E were established through the condensation of cyclohexanone and commercially available 4-methoxy-2,3-dimethylaniline, followed by PdII -catalyzed dehydrogenative aromatization/intramolecular C-C bond coupling and deprotection. A chiral dinuclear vanadium complex (Ra ,S,S)-6 mediated the enantioselective oxidative coupling of sorazolon E, affording (+)-sorazolon E2 in good enantioselectivity.

Chiral Organocatalyzed Intermolecular Rauhut–Currier Reaction of Nitroalkenes with Ethyl Allenoate

An enantioselective intermolecular Rauhut-Currier (RC) reaction of nitroalkenes with ethyl allenoate has been established with quinidine-derived β-isocupreidine. The present RC reaction afforded α-functionalized allenoates 3 in up to 94% yield with 59% enantiomeric excess (ee).

Vanadium-Catalyzed Dehydrogenation of N-Heterocycles in Water

In this paper, the dehydrogenation of tetrahydroquinolines using oxovanadium(V) catalysts under mild conditions in water and oxygen atmosphere is described. This catalytic technology was successfully applied to a range of other structurally related N-heterocycles, and a reaction mechanism is proposed.

Asymmetric oxidative coupling of hydroxycarbazoles: Facile synthesis of (+)-bi-2-hydroxy-3-methylcarbazole

Asymmetric oxidative coupling reactions of hydroxycarbazoles have been established using a chiral dinuclear vanadium complex. To demonstrate the utility of vanadium-catalyzed reactions, we have used them to synthesize (+)-bi-2-hydroxy-3-carbazole in three steps from cyclohexanone and commercially available aniline derivatives.