A new approach to dihydrobenzofurans and dihydrobenzopyrans (chromans) based on the intramolecular trapping by alcohols of benzynes generated from 7-substituted-1-aminobenzotriazoles

1-Aminobenzotriazoles 9 having 7-hydroxyalkyl substituents are efficiently converted into the corresponding benzynes 4 when treated with N-iodosuccini mide which then undergo highly efficient intramolecular trapping by the pen dant hydroxyl groups leading to dihydrobenzofurans 24-26 and dihydrobenzopy rans (chromans) 27, with incorporation of a synthetically useful iodine ato m adjacent to the new ether bond, which allows subsequent and high-yielding homologations using Stipe, Sonogashira and Heck couplings. (C) 2000 Elsevi er Science Ltd. All rights reserved.