Synthesis of 2-Aryl Acetophenones via Hydrobromination and Oxy-isomerization of (-Arylethynyl)benzyl Alcohols.

Hydrobromination and oxy-isomerization of (-arylethynyl)benzyl alcohols to yield brominated aryl ketones were achieved with bromotrimethylsilane. The substrate scope suggested that vinyl carbocations, stabilized by the conjugated aryl groups, are the reaction intermediates. 1-Isochromene was also detected by H NMR, and an isolated 1-isochromene was converted to the product when retreated with TMSBr. The formation of 1-isochromene is equivalent to a 6- cyclization and contrasts with the corresponding reactions under basic conditions, in which the 5- process dominated.