LEWIS-ACID CATALYZED REACTION OF CINNAMANILIDES - COMPETITION OF INTRAMOLECULAR AND INTERMOLECULAR FRIEDEL-CRAFTS REACTION

The first intermolecular Friedel-Crafts reaction of benzene leading to the formation of 3,3-diphenylpropionanilide 7 is described. 4-Methoxy aniline was reacted with cinnamoyl chloride to give 4-methoxycinnamani lide (5a), the treatment of which with aluminum(III) chloride in chlor obenzene at 120 degrees C or in benzene at 80 degrees C afforded exclu sively 6-hydroxyquinolin-2(1H)-one (3a) or 4'-hydroxy-3,3-diphenylprop ionanilide (7a), respectively. The formation of 7a rather than 3a in b enzene indicated that an intermolecular Friedel-Crafts reaction occurr ed prior to the relatively more facile intramolecular ring cyclization . This intermolecular Friedel-Crafts reaction was observed during the attempted ring cyclization of cinnamanilide and its methoxy derivative s in aluminum(III) chloride/benzene. Preparation of 3a can also be ach ieved in 17% overall yield via the N-oxidation of 6-hydroxyquinoline f ollowed by acetylation and hydrolysis.