A new reaction of acid chlorides. Intramolecular ortho-chlorination

Abstract

2-(2-Arylazophenoxy)-2-methylpropanoic acids (1) react with thionyl chloride to form 4-(2-chloroanilino)-benzoxazinones (3) in high yield. The reaction proceeds through the acid chloride which undergoes cyclisation with intramolecular electrophilic transfer of the chlorine to ring B. This selective ortho-chlorination is general for azo-acids (1) in which ring B contains a free ortho-position and –M groups are absent.

2-(2,6-Dimethylphenylazophenoxy)-2-methylpropanoic acid reacts to give the 4-(4-chloro-2,6-dimethylanilino)benzoxazinone but this para-chlorination (and a little dichlorination) is probably an intermolecular process.