Ciba-geigy Corporation

Wolfgang J Tritschler

Rudolf Maul

Heinz Steiner

Helmut Prestel

Gary Clauson

Jere K Kaplan

2-(2-Hydroxyphenyl)-2H-benzotriazoles can be prepared particularly advantageously by catalytically reducing a suitable o-nitroazobenzene compound to the corresponding N-oxybenzotriazole compound in the presence of hydrazine hydrate, a metal catalyst selected from the group consisting of Raney-Ni and the noble metals, an organic or inorganic base, an organic solvent, and optionally water; followed by isolating said N-oxybenzotriazole compound and converting it to the corresponding 2-(2-hydroxyphenyl)-2H-benzotriazole.

Process for the preparation of benzotriazoles

A process for the preparation of compounds of formula I ##STR1## wherein R.sub.1 and R.sub.2 are each independently of the other hydrogen, C.sub.1 -C.sub.12 alkyl, C.sub.5 -C.sub.6 cycloalkyl or phenyl, and R.sub.3 and R.sub.4 are each independently of the other C.sub.1 -C.sub.18 alkyl, C.sub.5 -C.sub.6 cycloalkyl, phenyl, phenyl which is substituted by C.sub.1 -C.sub.6 alkyl and/or hydroxy, or phenyl-C.sub.1 -C.sub.4 alkyl. The process comprises reacting a compound of formula III ##STR2## with a nitrite in aqueous or aqueous/organic medium to a compound of formula II ##STR3## extracting said compound of formula II from the reaction solution with a solvent, hydrogenating said compound, without isolation, in the cited solvent and in the presence of a palladium catalyst, to the corresponding p-aminophenol, and reacting said aminophenol, without isolation, with cyanuric chloride and a compound of formula HSR.sub.3 or HSR.sub.4 or a mixture of compounds of formulae HSR.sub.3 and HSR.sub.4. The products are obtained in high yield and purity.

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Bad Sackingen, Germany

Wolfgang J Tritschler