Facile Synthesis of the Fused 6-6-5 Ring System Containing Chroman Ring from 2-(1-Hydroxy-5-alkenyl)phenol Derivatives via Intramolecular Inverse-Electron-Demand Diels-Alder Reaction

摘要

A simple and facile synthesis of the fused 6-6-5 ring system, i.e., 1,2,3,3a,4,9b-hexahydrocyclopenta[c][1]benzopyrans, was achieved through the intramolecular [4+2] cycloaddition of o-quinonemethides generated from 2-(1-hydroxy-5-alkenyl)phenol derivatives under acidic conditions.In general, cis-fused tricyclic compounds of 6-6-5 ring system were obtained as the major products. Reactivity and selectivity of the cycloaddition reaction depended on the substituents on the aromatic ring and in the dienophilic olefine moiety.