Triazines and related products. Part 20. Oxidation of 1-(arylazo)-piperidines with potassium permanganate

Abstract

Oxidation of 1-(4-chlorophenylazo)piperidine with aqueous potassium permanganate afforded 4-chloroaniline, 1,3-bis-(4-chlorophenyl)triazene, and the oxidised triazenes 1-(4-chlorophenylazo)piperidin-2-one, -4-one, -3-ol, and -4-ol, and 1-(4-chlorophenylazo)-1,2,3,4-tetrahydropyridine. Oxidation of 4-amino-2-[2-(piperidin-1-ylazo)pheny]quinazoline yielded 4-amino-2-(2-aminophenyl)quinazoline and 1-[2-(4-aminoquinazolin-2-yl)phenylazo]piperidin-2-one.

Hydrolysis of 1-(4-chlorophenylazo)piperidin-2-one with 0.1 N-potassium hydroxide in the dark yielded 4-chloroaniline and valerolactone. Valerolactone was also identified as an oxidation product from treatment of 4-amino-2-[2-(piperidin-1-ylazo)phenyl]quinazoline and N-nitrosopiperidine with permanganate. Oxidation at the α-position of the piperidine ring is an activating step in the development of alkylating activity in 1-(arylazo)piperidines: a mechanism for this process is proposed.