Diels–Alder Reactions of α-Cyano α,β-Unsaturated Ketones with 2-Methyl-1,3-Butadiene: DFT Study of Mechanism, Reactivity and Regioselectivity

Abstract

The mechanism, reactivity and regioselectivity of Diels–Alder cycloaddition reactions of 2-methyl-1,3-butadiene with four dienophiles, ( E)-2-benzylidene-3-oxobutanenitrile, ( E)-2-(furan-2-ylmethylene)-3-oxopentanenitrile, ( E)-2-benzylidene-4,4-dimethyl-3-oxopentanenitrile, and (E)-2-benzoyl-3-(furan-2-yl) acrylonitrile, have been studied by means of several theoretical approaches. The regioselectivity of these reactions has been confirmed by their activation energies, the Gazquez–Mendez rule, Houk's rule and global descriptors of the products. All the studied reactions have normal electron demand character and a polar nature. All calculations were done at the DFT-B3LYP/6-31G(d) level of theory.