Rhodium‐Catalyzed Synthesis of Trisubstituted Olefins from Ethene Derivatives and Diazoalkanes

Synthesis of square-planar carbene complexes was the goal, but a novel catalytic olefin synthesis was the result. A mixture of diphenyldiazomethane and its derivatives 1 with ethene, propene, or styrene provided, in the presence of catalytic amounts of [{RhCl(C2H4)2}2], a good yield of the olefins 2, with turnover numbers as high as 500 (R  H, Me, Ph; R′  H, Me, Cl, etc.).