PtCl2-catalyzed reactions of o-alkynylanilines with ethyl propiolate and dimethyl acetylenedicarboxylate

The PtCl2-catalyzed reactions between indoles and ethyl propiolate gave rise to mono and double addition products. The composition of the products was largely influenced by the substituents on the indoles as well as the amount of ethyl propiolate used. o-Alkynylanilines reacted with ethyl propiolate and dimethyl acetylenedicarboxylate under the catalysis of PtCl2 to generate the corresponding 2,3-disubstituted indoles. The reaction proceeded by following a sequential cyclization/intermolecular addition pathway.