Mechanistic Investigation on Scandium-Catalyzed C–H Addition of Pyridines to Olefins

Abstract

This paper reports computational studies on the ortho alkylation of pyridines via C–H addition to olefins catalyzed by cationic half-sandwich rare-earth alkyl species. A detailed mechanism concerning the generation of catalytically active species and C–H addition has been computationally investigated at the molecular and electronic levels. The results support the mechanism based on experiments, which involves the initial generation of a metal pyridyl active species, followed by the coordination and insertion of an olefin and the subsequent pyridine C–H activation by a metal–carbon bond. The o-methyl sp3 C–H activation product of α-picoline has been also calculated, and the results suggest that the sp3 C–H activation product mainly results from the conversion of the sp2 C–H activation product of α-picoline rather than from the direct reaction of the cationic species (η5-C5Me5)Sc(CH2C6H4NMe2-o)+ with α-picoline, and such a conversion is reversible. The reaction rate of the whole process is controlled by the...