Thermal and Lewis acid-promoted asymmetric hetero Diels–Alder reaction of a 1-thiabuta-1,3-diene system (thiochalcone) with chiral acrylic esters and N-acryloyl- and N-crotonyl-carboximides

Abstract

Thermal and Lewis acid-promoted asymmetric hetero Diels–Alder reactions of the thiabutadiene 1 with the chiral dienophiles 2–5 derived from (–)-menthol, (+)-borneol and (–)-4-benzyloxazolidinone affords the optically active dihydrothiopyran derivatives. The chiral induction is in the range 13–92% d.e. depending mainly upon the auxiliary chiral groups. The absolute configuration of the endo cycloadducts is confirmed by the derivatization based on X-ray crystallographic analysis.