Tandem aminocarbonylation/Pauson-Khand reaction of haloacetylenes

[GRAPHICS] The dicobalt hexacarbonyl complex of 1-chloro-2-phenylacetylene decomposes in solution at room temperature affording similar amounts of two new comple xes, to which the structures of a dichloro tetracobalt decacarbonyl complex of 1,4-diphenyl-1,3-butadiyne and of a 1-chloro-2-phenylacetylene acylcoba lt complex have been tentatively assigned. The acyl complex can he efficien tly trapped by amines, and the resulting aminocarbonylation products submit ted to Pauson-Khand reaction to yield cyclopentenones with the regiocontrol led formation of five new bonds in a single synthetic operation.