Internuclear cyclisation. Part XXI. Thermal decomposition of diazonium sulphates from alkoxy-N-alkyl-2-aminobenzanilides

Abstract

Thermal decomposition of aqueous solutions of the diazonium sulphates from alkoxy-N-alkyl-2-aminobenzanilides results in the formation of the 5-, 6-, and 7-membered heterocyclic systems, isoindolinones, phenanthridones, and oxazepinones, respectively. Formation of the isoindolinones involves loss of the alkyl group from a 2′- or 4′-alkoxy-group, and formation of the oxazepinones involves its loss from a 2′-alkoxy-group; however, when these reactions are possible they predominate over “normal” ring-closure to the alkoxyphenanthridones. Loss of methyl from a 4′-methoxy-group to give a cross-conjugated cyclohexadienone is favoured over its loss from a 2′-methoxy-group to give the linearly-conjugated system.

Electrophilic attack by the decomposing diazonium ion on all the available intramolecular nucleophilic centres has thus been observed.