Substituent effects in the bis(benzotriazolylmethylation) of aromatic amines

Abstract

1-(Hydroxymethyl)benzotriazole and aromatic amines react to give an equilibrium mixture of N-mono- and N,N-bis(benzotriazolylmethyl)arylamines. Electron-releasing substituents on the arylamine ring shift the equilibrium towards the N,N-bis(benzotriazolylmethylated) products, and removal of water formed in the reaction leads to these bis derivatives in quantitative yields. These products were isolated as mixtures of three isomers, the benzotriazolyl-1,1′, -1,2′, and -2,2′ derivatives; these mixtures were characterized by full assignment of their 13CNMR spectra and by partial separation and enrichment. Electron-withdrawing substituents on the arylamine ring increase the isomer interconversion energy barriers and make N,N-bis(benzotriazolylmethyl)arylamines more resistant to hydrolysis. A strong influence of ortho alkyl groups on the stability and NMR spectral properties of N,N-bis(benzotriazolylmethyl)arylamines is interpreted on the basis of steric hindrance. Keywords: Mannich reaction, benzotriazole isomerization, substituent effects, anilines, bis(benzotriazolylmethyl)arylamines.