Synthetic Reactions by Complex Catalysts. XIV. Reaction of Isocyanide with Amine Catalyzed by Group IB and IIB Metal Compounds

Abstract

Abstract Group IB and IIB metal compounds catalyze the reaction of isocyanides (1) with amines (2) producing formamidines (3). In the reaction of cyclohexyl isocyanide with piperidine, the accelerating effect of catalyst was in the order AgCl>CuCl>>ZnCl2, Cd(OAc)2, HAuCl4·4H2O. The AgCl catalyzed reaction proceeded almost quantitatively in 2.5 hr at 17°C. The reaction of aliphatic isocyanide with aromatic amine, e.g., N-methylaniline, required higher reaction temperatures (160°C) even in the presence of catalyst, in which the order of catalytic activity was HAuCl4·4H2O>ZnCl2>AgCl>>CuCl. A ternary complex of (CuCl)2 (cyclohexyl isocyanide)2 (piperidine) was isolated, which was unstable and decomposed gradually at room temperature to give N-cyclohexyl-N,N′-pentamethylene formamidine. A mechanism through a mixed ligand complex has been proposed, in which both isocyanide and amine are coordinated with the same metal ion and the reaction takes place in the sphere of complex ligand.