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4 results on '"Ojima, Rihaku"'

2. Construction of 1,3‐Nonadjacent Stereogenic Centers Through Enantioselective Addition of α‐Thioacetamides to α‐Substituted Vinyl Sulfones Catalyzed by Chiral Strong Brønsted Base.

Author

Kondoh, Azusa, Ojima, Rihaku, Ishikawa, Sho, and Terada, Masahiro

Subjects
*BASE catalysts, *SULFONES, *ADDITION reactions, *ALKYL group, *ASYMMETRIC synthesis, *CATALYSTS
Abstract

An enantioselective addition reaction for the construction of 1,3‐nonadjacent stereogenic centers is developed by means of a chiral strong Brønsted base catalyst. The chiral sodium ureate catalyst efficiently promoted the reaction of α‐thioacetamides as less acidic pronucleophiles with vinyl sulfones having a variety of α‐substituents including aryl, alkyl and halo groups, and α‐phenylacrylates, accomplishing the construction of various 1,3‐nonadjacent stereogenic centers in highly diastereo‐ and enantioselective manners. This is a rare example of the construction of 1,3‐nonadjacent stereogenic centers with less acidic pronucleophiles. In addition, the application of Michael acceptors having various types of α‐substituents in a single catalyst system is achieved for the first time, demonstrating the utility of the present catalyst system for the construction of 1,3‐nonadjacent stereogenic centers. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Brønsted Base-Catalyzed Reductive Deimination of α-Iminoketones

Author

Kondoh, Azusa, Inoue, Seitaro, Ojima, Rihaku, and Terada, Masahiro

Abstract

An unprecedented reductive deimination of α-iminoketones derived from benzils was developed under Brønsted base catalysis. Treatment of α-iminoketones with silanethiols in the presence of a catalytic amount of P2-tBu provided the corresponding arylbenzylketones in good yields. This is a rare example of the direct transformation of an imine moiety into a methylene moiety.An unprecedented reductive deimination of α-iminoketones was developed under Brønsted base catalysis. Treatment of α-iminoketones with silanethiols in the presence of a catalytic amount of P2-tBu provided the corresponding aryl benzyl ketones in good yields. This is a rare example of the direct transformation of an imine moiety into a methylene moiety.

Published
2023
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