Synthesis and transformations of phthalanylideneammonium salts

Abstract

Several phthalanylideneammonium perchlorates have been prepared by the action of acetic anhydride and perchloric acid on NN-disubstituted o-acylbenzamides. 3-Benzylidenephthalan-1-ylidenedimethylammonium perchlorate (3a) reacts with hydrazine, methylhydrazine, and phenylhydrazine to give derivatives of phthalazine, and with benzylamine in acetic acid to yield the hydroperchlorate of an isoindoline. Treatment with ethanolic benzyl-amine results in rearrangement to give 3-benzylamino-2-phenylinden-1-one; analogous compounds are formed by reaction with ammonia, aniline, dimethylamine, and methanolic triethylamine. Ethyl cyanoacetate and cyanoacetamide similarly yield derivatives of 2-phenylindan-1-one. Cyclisation of o-isobutyryl-NN-dimethylbenzamide gives 3-acetoxy-3-isopropylphthalan-1-ylidenedimethylammonium perchlorate (23) which has been converted into the isopropylidene analogue (25a) of compound (3a). The preparation of the corresponding diphenyl-methylene perchlorate (25b) is also reported. The latter two salts react with ethyl cyanoacetate without rearrangement to yield derivatives of 1,3-dimethylenephthalan.