Addition of α-polyhalides to olefins under mild reaction conditions, catalyzed by Mo(CO)6

Mo(CO)6 was found to be an efficient pre-catalyst in the 1,2-addition reaction of α-polyhalides to various olefins. Significantly, the reaction was run under mild conditions, viz. refluxing acetonitrile, with satisfactory yields. Cr(CO)6 was also studied but found to be inferior relative to the Mo complex. It was assumed that the active catalytic species is (CH3CN)3Mo(CO)3, generated in situ. The polyhalides examined were CCl4 and ethyl trichloroacetate. Acyclic, as well as cyclic olefins, and dienes were studied. A cyclization product, substituted [3.3.0]bicyclooctane, was generated starting from 1,5-cyclooctadiene. Whenever relevant and feasible, the stereochemistry of the addition product was elucidated. A catalytic cycle for the addition reaction was proposed.