Bifunctional amino sulfonamide-catalyzed asymmetric conjugate addition to alkenyl alkynyl ketimines as enone surrogates

Design and Synthesis of Phenylcyclopropane-Based Secondary Amine Catalysts and Their Applications in Asymmetric Reactions

Most chiral secondary amine catalysts are usually synthesized from chiral amino acids and their derivatives. On the other hand, the amine catalysts based on a binaphthyl backbone have previously been developed, and show unique chemo- and stereoselectivity in some asymmetric reactions. In spite of their utility, however, the applications of binaphthyl-based amines in asymmetric reactions are still rare due to their synthetic inefficiency. In this context, we designed amine catalysts possessing a phenylcyclopropane scaffold as a novel chiral motif. The novel catalysts could be synthesized easily and construct a similar chiral environment to that of binaphthyl-based amine catalysts. In addition, the phenylcyclopropane-based amino sulfonamide was found to be an effective catalyst for the syn-selective Mannich reaction and conjugate addition using alkynyl Z-ketimines.

Design of Bifunctional Amino Tf-Amide Organocatalysts and Application in Various Asymmetric Transformations

In this personal account, we describe our recent developments on the four types of amino Tf-amide catalysts in asymmetric transformations. Firstly, axially chiral biaryl-based secondary-amino Tf-amide catalyzed various stereoselective reactions via enamine intermediates. Secondly, pyrrolidine-based secondary-amino aliphatic Tf-amide catalyzed asymmetric direct Mannich reaction. Thirdly, chiral primary-amino aliphatic Tf-amide catalyzed asymmetric direct aldol reaction and conjugate addition. Finally, modified chiral amino aromatic Tf-amide catalyzed asymmetric transformations. These four different strategies are illustrated by using various organocatalyzed asymmetric transformations.

Asymmetric catalytic alkynylation of thiazolones and azlactones for synthesis of quaternary α-amino acid precursors

Asymmetric alkynylation of thiazolones and azlactones with alkynylbenziodoxolones as the electrophilic alkyne source catalyzed by thiourea phosphonium salt is described. By using thiazolones as nucleophiles, the desired alkyne functionalized thiazolones were obtained in 55-89% yields with 31-86% ee. Azlactones gave the desired products in comparable yields with lower enantioselectivities. Ring-opening of the alkynylation products led to α,α-disubstituted α-amino acid derivatives efficiently without loss of enantioselectivity.