Nickel-palladium-catalyzed hydroamination/cyclization of sulfur-substituted 1,6-diynes with secondary amines

Hydroamination/cyclizations of sulfur-substituted 1,6-diynes catalyzed by nickel or nickel-palladium in DMSO were examined. Pyrroles 2a-l and furans 5a-i bearing various secondary amines were obtained in high yields. The organosulfanylmethyl group on pyrroles was easily oxidized with ceric ammonium nitrate to produce the pyrrolecarboxaldehyde and corresponding acetal.