IMPACT OF LEWIS ACID CATALYST ON THE REGIOSELECTIVITY AND KINETICS OF 1, 3-DIPOLAR CYCLOADDITION REACTION OF AZIDOBENZENE WITH ACROLEIN: A THEORETICAL STUDY USING DFT

In the present work, impact of Lewis acid (LA) catalysts BF3, BCl3, and BBr3 on the kinetics and regioselectivity of 1,3-dipolar cycloaddition (1,3-DC) reaction between azidobenzene and acrolein was theoretically studied using B3LYP/6-31G* level. Our results indicate while the uncatalyzed 1,3DC reaction under investigation takes place via a non-polar, non-regioselective, and low asynchronous process, the LA catalyzed 1,3-DC reaction takes place via a polar, regioselective, and high asynchronous process. In addition, the barrier height of the studied 1,3-DC reaction is considerably reduced in the presence of LA catalysts, and the catalytic activity of LAs in order to increase the electrophilicity character of acrolein and, consequently, to reduce barrier height of reaction, is increased with the increase of halogen atom size; BBr3> BCl3> BF3. Regioselectivity in these LA catalyzed 1, 3-DC reactions appears to be controlled by steric repulsion effects between the LA catalyst and the azide phenyl substituent instead of the electronic effects.