NEW UV ABSORBERS BASED ON N-(2-AMINOARYL)BENZOTRIAZOLES

A joint method for the synthesis of 1-(2-aminoaryl)-1H- and 2-(2-aminoaryl)-2H-benzotriazoles including the SNAr reaction of 1H-benzotriazole with ortho-nitrogalogenarenes and the reduction of the resulting mixture of isomeric nitro derivatives of benzotriazole, was developed. The influence of the temperature and structure of the electrophile on the selectivity of the SNAr reaction was studied. 1-(2-Nitroaryl)-1H-benzotriazole was mainly formed at high temperature. The amount of 2-(2-nitroaryl)-2H-benzotriazole increased with a decrease in the reaction temperature. The highest selectivity for 2-substituted 2H-benzotriazole was observed at 40 ºC. The electron deficiency character of the electrophile had a significant effect on the ratio of isomers formed in the substitution reaction. The amount of 2-substituted isomer in the reaction mixture became smaller with its increase. The effect of hydrochloric acid concentration on the course of the main and side processes during the reduction of N-nitroaryl derivatives of benzotriazole with tin (II) chloride in an acidic aqueous alcohol medium was studied. The use of 9% HCl led to the formation of azoxy compounds – condensation products intermediately formed during the reduction of nitroso- and hydroxylamine derivatives. Alkylation of 1-(2-aminoaryl)-1H-benzotriazole occurred in 36% HCl with alcohol used as a solvent. There were no by-products during the reduction in the i-PrOH/18% HCl system. The total yield of isomeric amino derivatives of benzotriazole was 96-99%. Separation of 1-(2-aminoaryl)-1H- and 2-(2-aminoaryl)-2H-benzotriazoles was based on the different polarity of the isomers and, accordingly, solubility in a nonpolar solvent – petroleum ether. The resulting N-(2-aminoaryl)benzotriazoles absorbed UV radiation in both the short-wave, medium- and near-wave ultraviolet ranges of the electromagnetic spectrum. 1-Substituted benzotriazoles were more effective UV absorbers in the UVC region than 2-aryl derivatives and Tinuvin P. By the ability to absorb medium-wave UV radiation 1-(2-aminoaryl)-1H-benzotriazoles were significantly inferior to the corresponding isomeric 2-(2-aminoaryl)derivative. The presence of 2-(2-aminoaryl)-2H-benzotriazole acceptor substituents enhanced the ability of the substance to absorb UV radiation compared with 2-(2-aminophenyl)-2H-benzotriazole. 2-Substituted benzotriazoles were more effective ultraviolet adsorbers in the UVB region than Tinuvin P. 2-(2-Aminophenyl)-2H-benzotriazoles also absorbed ultraviolet radiation in the range of 315-400 nm more actively than 1-substituted analogues, but were partly inferior to a commercial photostabilizer. For citation: Begunov R.S., Khlopotinin A.I., Lobanova L.V., Vorontsov S.M., Savina L.I., Danilova A.S. New UV absorbers based on N-(2-aminoaryl)benzotriazoles. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 11. P. 86-94. DOI: 10.6060/ivkkt.20246711.7070.