Intramolecular nitrene insertions into aromatic and heteroaromatic systmes. Part 7. Insertions into electron-deficient rings

Abstract

A number of routes to o-aminotriphenylmethanes are described, where one benzene ring, or both, carry potential ester groups. The most useful synthon is shown to be the 1,3-dioxan-2-yl substituent, and using this methyl 2-aminodiphenylmethane-4′-carboxylate (18) and dimethyl 2-aminotriphenylmethane-4′,4″-dicarboxylate (28) have been prepared. The azides from these, respectively (19) and (29), on thermolysis at 200 °C gave azepino-indoles (48) and (51), the first examples of ring expansion by an arylnitrene of benzene rings with electron-with drawing substituents. Also reported are syntheses of 3- and 4-(2-azidobenzyl)pyridines (38) and (39), and of 2-(2-azidobenzyl)thiazole (40); decomposition of these azides gave mainly polymers.