Synthesis of Fluorine Containing Polyfunctional Aromatic Compounds —Sandmeyer Synthesis of 4-Halo-3-trifluoromethylbenzonitriles—

Abstract

An effective synthesis of a series of fluorine-containing polyfunctional aromatic compounds, 4-halo-3-trifluoromethylbenzonitriles 1a–c was performed by the use of some tetrahedral copper-cyano complexes as Sandmeyer cyanating reagents and sublimation in the isolation and purification process. In the conversion of the corresponding diazonium salts to the target benzonitrile derivatives (1a–c), three tetrahedral tetracyanocopper complexes, K₃[Cu(CN)₄], Na₃[Cu(CN)₄], and K₂[Cu(CN)₄ · NH₃], proved to be effective as Sandmeyer cyanating reagents though copper(I) cyanide gave the target compounds in moderate yields. Furthermore, the yields of nitriles 1a–c in the reaction with the copper(I) complexes were rather higher than that with the copper(II) complex, K₂[Cu(CN)₄ · NH₃]. The conversion reactions to nitriles 1a–c are suggested to proceed through an S_NAr mechanism.