Rh-PNP Pincer Ligand Complex Catalyzed Alkyne Dimerization

Significance

Homodimerization of terminal alkynes was achieved by using a Rh PNP-pincer-type ligand complex, which is relatively moisture- and air-stable. The regio- and geometric selectivities were very high affording the E-enyne isomer in high conversion with relatively low catalyst loading (0.5 mo%) in benzene. A broad range of substrates are compatible, such as aryl, alkyl, and silyl. It is particularly attractive that free hydroxy or amino groups were tolerated. In the case of the electron-poor alkyne HCCCO₂Et, however, the predominant reaction is cyclotrimerization.