A new approach to dihydrobenzofurans by intramolecular trapping of benzynes by hydroxyl functions

The adducts 3, derived from condensations of the 1-aminobenzotriazole dianion 2 and aldehydes or ketones, are converted into the corresponding benzynes upon exposure to either N-bromosuccinimide or lead(IV) acetate; intramolecular trapping by the hydroxyl group then leads to the dihydrobenzofurans 4, 7, 8 and 9 in 38–75% isolated yields.