A general and practicable synthesis of polycyclic heteroaromatic compounds. Part 4. A rationale for the mechanism of the synthesis

Abstract

Studies on aspects of the mechanism of our general synthesis of polycyclic heteroaromatic compounds suggest that the reaction sequence outlined in Scheme 2 is followed. Under the conditions of our synthesis, the ortho-rearrangement (8)→(9) is preferred to the para-rearrangement which is known to occur in acid conditions. Aniline Mannich bases (29) are converted to benz[a]acridines (30) in an intermolecular reaction. The synthesis appears to be restricted to substrates where the putative intermediate (9) is not part of an amide group. In the course of these studies effective syntheses of the tricyclic compounds (24) and (25) have been discovered.