摘要:
The palladium-catalyzed carbonylative ring-forming reactions of 2-iodothiophenol, and the corresponding substituted derivatives, with allenes and carbon monoxide are described. The reactions afford thiochroman-4-ones in good to excellent isolated yields with quite high regioselectivity. The catalytic heteroannulation may involve regioselective addition of the sulfur moiety of the reactants on the more positive end of the allene, arylpalladium formation, CO insertion, subsequent intramolecular cyclization, and then reductive elimination. The regioselectivity is probably governed by electronic effects.