Stereoselective Synthesis of Benzofuran and Benzothiophene Substituted Dihydropyran Derivatives Via Ring Closing Metathesis

Abstract

Ring closing metathesis reactions have been applied to diene and enyne systems derived from homoallylic alcohol backbones are described. The key intermediates 2-benzofuranyl la and 2-benzothiophenyl lb substituted homoallylic alcohols were synthesized from their corresponding carboxaldehyde derivatives. Racemic 2-heteroaryl-substituted homoallylic alcohols are successfully resolved to give the corresponding enantiopure acetates and alcohols with 80-99% ee through enzymatic resolution by various lipases. Enantiomerically enriched diene and enyne skeletons derived from homoallylic alcohols were subjected to the ring closing metathesis via first and second generation Grubbs' catalysts and the corresponding chiral heteroaryl-substituted dihydropyran derivatives were obtained with good yields (41-96%). (C) 2016 Elsevier Ltd. All rights reserved.