Cleavage of 2-acetyl-2-phenylazopropionanilide and related compounds by boron trifluoride. New Japp–Klingemann reactions

Abstract

2-Acetyl, 2-cyano-, and 2-nitro-2-phenylazopropionic acid derivatives suffer cleavage of the phenylazo-grouping on treatment with boron trifluoride, giving benzenediazonium tetrafluoroborate and the corresponding difluoroboron propionic acid derivative; 2-cyano- or 2-nitro-2-phenylazoisobutyronitrile and the corresponding amides behave similarly, but 1-phenylazo-2-naphthol gives a difluoroboron salt, and 2-phenylazo(diphenylmethyl)acetate is cyclised to 1,3-diphenylindazole on treatment with boron trifluoride. Acyl-2-phenylazopropionates suffer loss of the acyl grouping during attempted ketonic carbonyl condensation reactions, with conversion into corresponding phenylhydrazones; new examples, broadening the scope of the Japp–Klingemann reaction, are described.