Studies toward a model for the prediction of the regioselectivity in the Fischer indole synthesis

A preliminary model for the prediction of the regioselectivity in the Fischer indole synthesis has been deveLoped. It is based on the use of the energy differences between the starting compound and the energy maximum compound along an a priori chosen reaction coordinate calculated with the AM1 program. The modeL has been applied to three examples and its results are in agreement with the available experimental data. All the possible alternative intermediates have been considered in order to accurately verify the proposed multistep mechanism.