Rhodium-Catalyzed Chemo- and Regioselective Intermolecular Cross-Cyclotrimerization of Nonactivated Terminal and Internal Alkynes.

It has been established that a cationic rhodium(I)/BIPHEP complex is able to catalyze the unprecedented intermolecular cross-cyclotrimerization of nonactivated terminal and internal alkynes at room temperature. In this transformation, the use of arylacetylenes as terminal alkynes and 1,4-butynediol derivatives as internal alkynes afforded the cross-cyclotrimerization products with good chemo- and regioselectivity. The present study clearly demonstrated that an electronically biased combination of nonactivated and electron-deficient alkynes is not necessary to realize good chemo- and regioselectivity in the cationic rhodium(I) complex-catalyzed intermolecular cross-cyclotrimerization.