A new chiral axis due to N(open-chain imide)-Ar bond: Unexpected racemization effect of an acyl group

Abstract

The first example of optically active compound 3c which possesses axial chirality based on the N(open-chain imide)-Ar bond rotation, is described. Furthermore, a quite interesting result is also described, namely, that 3a bearing a bulky acyl group rather than a small one racemized more rapidly. To explain this phenomenon, 13C NMR experiments and the reaction with benzylamine of 3a-d were undertaken. These preliminary results suggest that the t-BuCO-N bond in 3a which racemized easily, is more twisted, compared with the CO-N bonds in 3b-d which were relatively stable to racemization.