Yuji Koseki

Stereoselective synthesis of tilivalline

Abstract Tilivalline (1b) was easily synthesized by converting lactam 3b to the acyliminium precursor 5b followed by stereoselectively introducing indole from the less hindered side of 5b.

Squaramide–Sulfonamide Organocatalyst for Asymmetric Direct Vinylogous Aldol Reactions

Asymmetric direct vinylogous aldol reactions of furan-2(5H)-one with aldehydes in the presence of a catalytic amount of novel squaramide-sulfonamide organocatalyst resulted in the corresponding addition products with high to excellent enantioselectivities. This is the first successful report illustrating an example of highly stereoselective reactions using a squaramide-sulfonamide organocatalyst.

Perfluoroalkanesulfonamide Organocatalysts for Asymmetric Conjugate Additions of Branched Aldehydes to Vinyl Sulfones

Asymmetric conjugate additions of branched aldehydes to vinyl sulfones promoted by sulfonamide organocatalyst 6 or 7 have been developed, allowing facile synthesis of the corresponding adducts with all-carbon quaternary stereocenters in excellent yields with up to 95% ee.

Asymmetric Conjugate Addition of Nitroalkanes to Enones Using a Sulfonamide–Thiourea Organocatalyst

The asymmetric conjugate addition of nitroalkanes to α,β-unsaturated ketones in the presence of a catalytic amount of a novel sulfonamide-thiourea organocatalyst resulted in the corresponding γ-nitro carbonyl products in high yields with excellent enantioselectivities (up to 97% ee).

Cinchona–Diaminomethylenemalononitrile Organocatalyst for the Highly Enantioselective Hydrophosphonylation of Ketones and Enones

The use of diaminomethylenemalononitrile (DMM) organocatalyst to promote the challenging 1,2-hydrophosphonylation of simple ketones and enones, which are also called α,β-unsaturated ketones, is proposed and validated. This reaction provided the corresponding chiral α-hydroxy phosphonates in high to excellent yields and with enantioselectivity up to 96% ee.

Asymmetric conjugate addition of α-cyanoketones to enones using diaminomethylenemalononitrile organocatalyst

A diaminomethylenemalononitrile organocatalyst efficiently catalyzed the asymmetric conjugate addition of α-cyanoketones to vinyl ketones to give the corresponding 1,5-dicarbonyl compounds, which bear an all-carbon quaternary stereogenic center with high enantioselectivities. This report is the first example of the asymmetric conjugate addition of α-cyanoketones to vinyl ketones using an organocatalyst.

Asymmetric Conjugate Additions of Carbonyl Compounds to Nitroalkenes under Solvent-Free Conditions Using Fluorous Diaminomethylenemalononitrile Organocatalyst

The novel fluorous organocatalyst bearing a diaminomethylenemalononitrile motif is prepared. The fluorous organocatalyst efficiently promotes asymmetric conjugate additions of ketones to nitroalkenes and results in high yields of these addition products with excellent enantioselectivities under solvent-free conditions.