Reactions of condensed N-heteroaromatic molecules. Part II. Electrophilic substitution of N-acetylcarbazole, N-acetyl-10,11-dihydrodibenz-[b,f]azepine, and derivatives

Abstract

N-Acetylation of carbazole and 10,11-dihydrodibenz[b,f]azepine deactivates the aromatic nuclei to electrophilic substitution. However, Friedel–Crafts acylation, catalysed by aluminium trichloride, proceeds smoothly to give high yields of the ring substitution products acylated meta to the nitrogen atom. Specific complexation of the N-acetyl derivative, aluminium trichloride, and acetyl chloride is thought to be involved, and the reaction appears to be general for a variety of N-heteroaromatic molecules. In contrast, the corresponding N-alkyl derivatives readily undergo electrophilic substitution para to the nitrogen atom.