Studies on reactions of anhydrides with Schiff bases

Reaction of phthalic anhydride 1 with benzylidineanilines 2, in equimolar ratio in hot acetic acid, yields N-arylphthalimides 3. Compound 1 reacts with the arylimine part of the Schiff base eliminating benzaldehyde part 4 as the bye-product. This reaction of 1 with 2 is also found to occur with other anhydrides like succinic anhydride 5, maleic anhydride 7 and acetic anhydride 9 resulting in the formation of the corresponding N-arylimides, namely, succinicimide 6, maleicimide 8 and aceticimide 10 respectively. In all the above reactions, the by-product, i.e. benzaldehyde or p-chlorobenzaldehyde can be isolated and characterized as its 2,4-dinitrophenylhydrazone derivative. Probable mechanism for the formation of imides from the corresponding anhydrides and Schiff bases has been suggested.