Mechanism of diethylamine/DBU-catalyzed cycloaddition of azides to unsaturated aldehydes: A quantum mechanical investigation

Abstract

Density functional theory (DFT) methods have been used to investigate the mechanism of diethylamine-catalyzed cycloaddition reaction of phenyl azide and pentanal. The single point energies have been computed at M06-2X/6-311+G(d,p)//M06-2X /6-31+G(d,p) levels of theory in the presence of DMSO as a solvent. The computational results indicate that the catalyzed cycloaddition reaction is carried out via two one-step transition states that lead to 1,4- and 1,5-regioisomers, and favors the generation of the 1,4-regioisomer. In the absence of a catalyst, the 32CA reactions of azide and alkyne lack poor regioselectivity. Finally, distortion/interaction analysis along the reaction pathways was used to explain the 1,5-regioselectivity.