A New Approach to Dihydrobenzofurans and Dihydrobenzopyrans (Chromans) Based on the Intramolecular Trapping by Alcohols of Benzynes Generated from 7-Substituted-1-aminobenzotriazoles

Abstract 1-Aminobenzotriazoles 9 having 7-hydroxyalkyl substituents are efficiently converted into the corresponding benzynes 4 when treated with N -iodosuccinimide which then undergo highly efficient intramolecular trapping by the pendant hydroxyl groups leading to dihydrobenzofurans 24 – 26 and dihydrobenzopyrans (chromans) 27 , with incorporation of a synthetically useful iodine atom adjacent to the new ether bond, which allows subsequent and high-yielding homologations using Stille, Sonogashira and Heck couplings.