CuI/La(OTf)₃-Catalyzed Synthesis of Isomeric Ellipticine

Significance

A CuI/La(OTf)₃-catalyzed tandem reaction for the efficient synthesis of isoellipticine derivatives in ionic liquid [bmim][BF4] has been developed. The reaction of imine 1 and aldehydes 2 with phenylacetylene (3) afforded products 4 in good yield. A series of different Lewis and Brøn­sted acids were investigated. The optimal reaction conditions were established. Different substituted aldehydes were examined (electron-poor or -rich and heteroaromatic). Even in the presence of electron-deficient aldehydes, such as 4-FC₆H₄CHO or electron-rich, such as 2,4,6-Me₃C₆H₂CHO, products 4 were produced in excellent yields. A possible mechanism for the reaction was proposed.