An expedient entry to chromane derivatives via indium-mediated intramolecular allenylation reactions

Starting from salicylaldehydes and 1,4-dibromo-2-butyne, preparation of chromane derivatives has been investigated. After attaching the bromobutynyl tether followed by intramolecular allenylation of aldehydes (or ketones) promoted by indium in aqueous (or organic) media, the chromane derivatives with allenic moiety have been efficiently constructed. The direct one-pot preparation of the chromanes has also been achieved.