title: Sequential enantiodivergent organocatalysis: reversibility in enantioswitching controlled by a conformationally flexible guanidine/bisthiourea organocatalyst.
abstract: Here we describe our studies on solvent-dependent enantiodivergent Mannich-type reactions utilizing conformationally flexible guanidine/bisthiourea organocatalyst (S,S)-1. Our mechanistic investigations revealed that the stereo-determining steps in both the (R)- and (S)-selective Mannich-type reactions are governed by the cooperative effect of guanidine and thiourea in the inherently monomeric structure of (S,S)-1. Based on the mechanistic similarity between the (R)- and (S)-selective Mannich-type reactions, we discovered that (S,S)-1-catalyzed reactions show unique reversibility in mixed solvent systems. We highlight the development of sequential enantiodivergent organocatalysis using (S,S)-1, which allows enantio-switching with single-flask operation and high in situ tunability.
authors.affiliation: Department of Biotechnology and Life Science, Faculty of Technology, Tokyo University of Agriculture and Technology, Koganei, Tokyo, Japan. sohtome@riken.jp
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sohtome
authors.forename: Takahisa
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: Shinji
authors.initials: S
authors.lastname: Tanaka
authors.forename: Kazuo
authors.initials: K
authors.lastname: Nagasawa
mesh_terms: D002384:Catalysis; D019791:Guanidine / Q000737:chemistry*; D008968:Molecular Conformation; D013237:Stereoisomerism; D013890:Thiourea / Q000031:analogs & derivatives / Q000737:chemistry*
chemical_list: D013890:Thiourea; D019791:Guanidine