Thermal and Lewis acid-promoted novel asymmetric hetero Diels–Alder reactions of a 1-thiabuta-1,3-diene system (thiochalcones) with (–)-dimenthyl fumarate

Abstract

Thermal and Lewis acid-promoted reactions of thiochalcones with (–)-dimenthyl fumarate gave two 3,4-cis-cycloadducts, 4 and 5, in good yields with 100%endo-diastereoselectivity and with a high level of diastereofacial selectivity. The major product 4 could be obtained stereochemically pure by recrystallization and this, when reduced with LiAlH₄, gave the optically active diol 6. The latter was converted into the acyclic diol 8 by Raney-Ni desulphurization.