Catalytic Availabilities of Lewis Acidic SnCl2: Ph3PAuCl–SnCl2 Composite Catalyzed Successive ortho-Alkenylation/O-Alkenylation of Phenols Followed by Cyclization to 1-Benzopyrans

A Ph3PAuCl-SnCl2 composite, prepared in situ from Ph3PAuCl and SnCl2, catalyzed the formation of 1-benzopyrans from phenols and phenylacetylene. The Ph3PAuCl-SnCl2 composite catalyzed reaction was presumed to proceed through the successive ortho-alkenylation and O-alkenylation of phenols with phenylacetylene followed by cyclization of the prepared ortho- and O-dialkenylated phenol derivatives. Conveniently, all reactions with Ph3PAuCl-SnCl2 composite were established without rigorous exclusion of air and water.