A THEORETICAL STUDY OF THE MECHANISM AND REGIOSELECTIVITY OF THE 1,3-DIPOLAR CYCLOADDITION REACTION OF AZIDES WITH ALKYNES

The mechanism and regioselectivities of the [3+2] cycloaddition reactions of the ethynylbenzene 4 and azide compounds 1, 2 and 3, have been theoretically studied using DFT methods at the B3LYP/6-31G(d) computational level. The possible ortho/meta regioselective channels were explored and characterized. The low polar character of these 32CA reactions is the consequence of the high nucleophilic character of both reagents. Analysis of the free energies associated with the different reaction pathways indicates that the 32CA reactions of the ethynyl-benzene 4 and azide compounds 1, 2 and 3 are highly meta regioselective, in agreement with the experimental observations.