Mechanistic considerations in the synthesis of 2-aryl-indole analogues under Bischler–Mohlau conditions. Issue 23 (3rd June 2015) - MacDonough, Matthew T.
Graphical abstract: Abstract: Mechanistic insight into the pathway of the Bischler–Mohlau indole formation reaction is provided by isotopic labeling utilizing judicious incorporation of a 13 C atom within the α-bromoacetophenone analogue reactant. The resulting rearranged 2-aryl indole, isolated as the major product, located the 13 C isotope label at the methine carbon of the fused five-membered heterocyclic ring, which suggested that the mechanistic pathway of cyclization, in this specific example, required two equivalents of the aniline analogue reactant partner and proceeded through an imine intermediate rather than by direct formation of the corresponding 3-aryl indole accompanied by a concomitant 1, 2-aryl shift rearrangement.