Synthesis of Polymer-supported Chiral 1,2-Diamine by Polycondensation and Its Application to Asymmetric Hydrogenation

摘要

Enantiopure C{sub}2-symmetric 1, 2-diamines such as 1, 2-diphenylethylenediamine, 1, 2-cyclohexanediamine have been known as an efficient chiral auxiliary in various kinds of chiral catalysts and reagents. Many examples of catalyst systems containing 1,2-diamine involve those used for epoxidations, Diels-Alder reactions, aldol reactions, dehydrations of olefins, nucleophilic additions of carbonyls, conjugate additions, protonation of enolates, cyclopropanations, aziridinations, and especially hydrogenations of ketone. Even though it is recognized that the combination of the 1, 2-diamine and RuCl{sub}2/BINAP is one of the most useful and powerful precatalyst system for asymmetric hydrogenation, little attention has been paid to preparation of the polymer-supported 1, 2-diamines. We have recently developed the synthesis of polymer-supported 1, 2-diamine by radical polymerization of N-Boc protected 1, 2-diamine with styryl group and styrene. The cross-linked polymers worked as efficient chiral ligands for asymmetric hydrogenation of acetophenone in DMF and in DMF/2-propanol, but not in 2-propanol only. Here in this study, we report the synthesis of novel polymer-supported chiral 1, 2-diamines by polycondensation of N-Boc protected 1, 2-diamine bearing two phenolic groups (and bisphenol) with dibromide. A representative example is illustrated in Scheme 1.