Regioselective carbonylative heteroannulation of o-iodothiophenols with allenes and carbon monoxide catalyzed by a palladium complex: A novel and efficient access to thiochroman-4-one derivatives
Wj. Xiao et H. Alper, Regioselective carbonylative heteroannulation of o-iodothiophenols with allenes and carbon monoxide catalyzed by a palladium complex: A novel and efficient access to thiochroman-4-one derivatives, J ORG CHEM, 64(26), 1999, pp. 9646-9652
The palladium-catalyzed carbonylative ring-forming reactions of 2-iodothiop
henol, and the corresponding substituted derivatives, with allenes and carb
on monoxide are described. The reactions afford thiochroman-4-ones in good
to excellent isolated yields with quite high regioselectivity. The catalyti
c heteroannulation may involve regioselective addition of the sulfur moiety
of the reactants on the more positive end of the allene, arylpalladium for
mation, CO insertion, subsequent intramolecular cyclization, and then reduc
tive elimination. The regioselectivity is probably governed by electronic e
ffects.