Synthesis and Characterization of Atrop­isomers Arising from 1,3-Cyclohexanediones by Intermolecular Tandem-Michael/Michael Additions

Crystal structures of proline-derived enamines

The isolation and structural characterization of both aldehyde- and ketone-derived proline enaminones are reported and discussed. Crystal structures of 10 proline enamines provide information on stereochemical aspects, i.e., double bond configuration and syn- vs. anti-positioning of the carboxylate relative to the enamine double bond. Furthermore, the obtained crystal structures are compared with the density functional theory-calculated structures of the ground and transition state and the postulated Seebach-Eschenmoser transition state.