Palladium-catalyzed indole and benzofuran ring formation accompanying carbonylation

The reaction of 2-(1-hexynyl)aniline with carbon monoxide in methanol under basic conditions is promoted by the catalytic action of palladium dichloride to give methyl 2-butylindole-3-carboxylate. Similarly, the reaction of 2-(1-hexynyl)-phenol under the same conditions gives methyl 2-butylbenzofuran-3-carboxylate. The carbonylative cyclization mentioned above is successful with the corresponding 2-phenylethynyl derivatives of aniline and phenol.