Tandem Aminocarbonylation/Pauson-Khand Reaction of Haloacetylenes

The dicobalt hexacarbonyl complex of 1-chloro-2-phenylacetylene decomposes in solution at room temperature affording similar amounts of two new complexes, to which the structures of a dichloro tetracobalt decacarbonyl complex of 1,4-diphenyl-1,3-butadiyne and of a 1-chloro-2-phenylacetylene acylcobalt complex have been tentatively assigned. The acyl complex can be efficiently trapped by amines, and the resulting aminocarbonylation products submitted to Pauson−Khand reaction to yield cyclopentenones with the regiocontrolled formation of five new bonds in a single synthetic operation.