Rh(I)-catalyzed intramolecular allenic Pauson-Khand reaction: construction of a bicyclo[5.3.0]dec-1,7-dien-9-one skeleton.

[reaction: see text] 1-Phenylsulfonylallenes possessing a hexynyl appendage in refluxing toluene in the presence of catalytic amount of rhodium(I) catalyst under a carbon monoxide atmosphere underwent regioselective formal [2 + 2 + 1]-cycloaddition to produce the corresponding bicyclo[5.3.0]dec-1,7-dien-9-one derivatives in acceptable yields.