An in-depth study of the azidobenzophenone–anthranil–acridone transformation

Abstract

The title transformation, particularly the conversion of anthranils into acridones, is shown to be critically sensitive to temperature, solvent, substituent, and metal catalysts. Thus the conversion of 3-(p-tolyl)-anthranil into an acridone gives a ratio of 2- and 3-methyl derivatives varying from 0.6:1 to 4.7:1 with changing temperature and solvent. In other similar thermolyses, solvents (e.g. 1,2,4-trichlorobenzene) were incorporated into the product and traces of metals and their derivatives had a dramatic effect on the rate and course of the reaction. The most effective catalysts were iron powder and aluminium acetylacetonate. 3-(2,6-Disubstituted phenyl)anthranils gave acridones in which the substituents were either lost or rearranged onto N or C, the last cases involving sequential [1,5]-sigmatropic shifts.

3-Thienylanthranils gave related thienoquinolones on thermolysis; again the reactions were very sensitive to catalysis. Blocked thienylanthranils also gave rearrangement products, but the non-aromatic intermediates could be isolated.