High-field ¹H N.M.R. study of the four-spin system of a set of 2,3,4,5-tetrasubstituted pyrrolidines

Abstract

The pyrrolidine ring protons of the isomeric dimethyl 2,5-dibenzoyl-1-phenylpyrrolidine- 3,4-dicarboxylates constitute, depending on stereochemistry, either an [AX]₂ or an ABXY system. The three types of spectra obtained have been analysed and correlated with molecular structure. Evidence is given for hydrogen bonding, between ester groups and cis-vicinal phenacyl hydrogen atoms, which leads to the stabilization of the preferred conformers.