Asymmetric Halocyclizations Of 2-Vinylbenzyl Alcohols With Chiral Flps

By the use of a chiral frustrated Lewis pair (FLP) consisting of a chiral-diene-derived borane and (Bu3P)-Bu-t as the catalyst, an asymmetric halocyclization of 2-vinylbenzyl alcohols with NBS or NIS was successfully realized. A variety of optically active 1,3-dihydroisobenofuran derivatives were obtained in high yields with up to 87% ee and could be conveniently converted to other useful chiral compounds.