Stereoselective synthesis of optically active dihydrofurans and dihydropyrans via a ring closing metathesis reaction

A ring closing metathesis reaction of dienes and a ring closing enyne metathesis reaction derived from allyl, homoallyl and homopropargyl alcohol backbones are described. 2-Heteroaryl substituted allyl, homoallyl and homopropargyl alcohols have been easily and efficiently resolved through enzymatic resolution with high ee (93-99%) and known stereochemistry. Enantiomerically enriched dienes derived from allyl and homoallyl alcohols afforded the corresponding enantiomerically enriched dihydrofuran and dihydropyran derivatives, respectively, with chemical yields which varied between 72% and 88%. On the other hand, enantiomerically enriched enynes derived from homoallyl and homopropargyl alcohols gave the corresponding optically active dihydropyrans with conjugated diene units with chemical yields between 70% and 80%. A subsequent Diels-Alder reaction of the dihydropyran derivatives with a diene unit with tetracyanoethylene resulted in the formation of a diastereomeric dihydroisochromene ring system as the sole product. (C) 2011 Elsevier Ltd. All rights reserved.