title: Substitution controlled functionalization of ortho-bromobenzylic alcohols via palladium catalysis: synthesis of chromenes and indenols.
abstract: An efficient domino Pd-catalyzed transformation of simple ortho-bromobenzyl tertiary alcohols to chromenes is presented. Their formation is believed to proceed via the formation of a five-membered palladacycle, which, in turn, involves in an intermolecular homocoupling with the second ortho-bromobenzyltertiary alcohol to yield the homo-biaryl bond followed by intramolecular C-O bond formation. Interestingly, when there is an allylic substituent on the benzylic carbon atom, a chemoselective switch was observed, which preferred intramolecular Heck coupling and gave indenols. Further, it has been confirmed that the tertiary alcohol functionality is indispensible to give the coupled products, whereas the use of primary/secondary benzylic alcohols furnished the simple carbonyl products via a possible reductive debromination followed by oxidation due to the availability of β-hydrogen(s).
authors: Department of Chemistry, Indian Institute of Technology , Hyderabad Ordnance Factory Estate Campus, Yeddumailaram 502 205, Medak District, Andhra Pradesh, India.
authors: Lodi
authors: L
authors: Mahendar
authors: Gedu
authors: G
authors: Satyanarayana