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

Article abstract of DOI:10.1016/S0040-4020(00)00021-1

1-Aminobenzotriazoles 9 having 7-hydroxyalkyl substituents are efficiently convened 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. (C) 2000 Elsevier Science Ltd.