Solid-state photochemistry: Absolute asymmetric beta-thiolactam synthesis from achiral N,N-dibenzyl-alpha,beta-unsaturated thioamides

摘要

Several types of achiral N,N-dibenzyl-alpha,beta-unsaturated thioamides were subjected to X-ray crystallographic analysis, and it was revealed that methylcrotonthioamide and 1-cyclohexenecarbothioamide provided chiral crystals. The absolute configuration determined by anomalous scattering method corresponded to the cotton effect in the solid-state CD spectra. The solid-state photoreaction gave optically active beta-thiolactams. On the other hand, E-Z isomerization takes place in the photoreaction of a tiglylthioamide derivative. Stereochemical assignment before and after the reaction was rationalized by the hydrogen abstraction by alkenyl carbon followed by cyclization via a zwitterionic intermediate. (C) 2000 Elsevier Science Ltd. All rights reserved. [References: 33]