Calix[4]arene-diphosphite rhodium complexes in solvent-free hydroaminovinylation of olefins

Abstract

Under solvent-free conditions rhodium complexes containing hemispherical diphosphites based on a calix[4]arene skeleton catalyse efficiently the hydroaminovinylation of α-olefins, thereby leading to high proportions of linear enamines/amines (when starting from secondary amines) or imines (when starting from primary amines). When applying a Rh/olefin ratio of 1 : 5000, the reaction turned out to be ca. 15 times faster than when operating in toluene at the same Rh/olefin ratio and at an olefin concentration of 6.6 mol L⁻¹. For example, in the hydroaminovinylation of 1-octene with piperidine using 5,11,17,23-tetra-tert-butyl-25,27-dipropyloxy-26,28-bis(1,1′binaphthyl-2,2′dioxyphosphanyloxy)calix[4]arene, TOFs up to 4640 mol(converted olefin).mol(Rh)⁻¹.h⁻¹ were observed (l/b ratio of 24.1).