A Computational Reinvestigation of the Formation of N-Alkylpyrroles via Intermolecular Redox Amination

A detailed mechanism of N-alkylpyrrole formation from 3-pyrroline and 2-phenylpropanal in the presence of a Bronsted acid catalyst was investigated in depth using the MP2 and DFT theories. The two mechanisms proposed earlier in recent literatures for this internal redox process were evaluated and were found not to account perfectly for the transition state and the energetic barrier of its formation. Based on the present calculations, a new mechanism was put forth.