Organocatalytic, Enantioselective, Intramolecular Oxa-Michael Reaction of Alkoxyboronate: A New Strategy for Enantioenriched 1-Substituted 1,3-Dihydroisobenzofurans

Abstract

An unprecedented strategy for the synthesis of enantioenriched 1-substituted 1,3-dihydroisobenzofurans via an enantioselective oxa-Michael reaction of o-alkoxyboronate containing chalcone (II) has been accomplished employing cinchona alkaloid based squaramide bifunctional organocatalyst in the presence of proton source. The corresponding alkoxyboronate intermediates have been readily prepared in situ from o-formyl chalcones using neutral borane as hydride source and a tertiary amine moiety which is a counterpart of the catalyst.