SYNTHESIS OF PHTHALIMIDINES . ACID-CATALYZED CYCLODEHYDRATION VERSUS CYCLODEAMINATION OF GAMMA-HYDROXYAMIDES OBTAINED FROM DILITHIO-N-SUBSTITUTED BENZAMIDES AND KETONES

An earlier method of preparation of γ‐hydroxyamides from N‐substituted benzamides and ketones or aldehydes by means of n‐butyllithium was improved and extended. The γ‐hydroxyamides were found to undergo cyclodehydration to form γ‐lactams with relatively strong acids, but cyclodeamination formed γ‐lactones with relatively weak acids; the γ‐lactams are substituted phthalimidines. The predominant course of cyclization was dependent also on the structure of the γ‐hydroxyamide. Certain γ‐hydroxyamides afforded phthalimidines with cold, concentrated sulfuric acid whereas certain others yielded γ‐lactones with this acid. The latter γ‐hydroxyamides, however, produced phthalimidines with the stronger acid, perchloric acid. The cyclodehydration reaction furnished a convenient and, apparently, quite general method for the synthesis of 2,3,3‐trisubstituted or 2,3‐disubstituted phthalimidines. Mechanisms are considered. Copyright © 1969 Journal of Heterocyclic Chemistry