ABINITIO TRANSITION STRUCTURES FOR DIELS-ALDER REACTIONS OF 2-AZABUTADIENE WITH ALKENES AND ALKYNES - EFFECTS OF SUBSTITUENTS, THE AZA GROUP, AND CATALYSIS ON REACTIVITY

Transition structures for the Diels-Alder reactions of 2-azabutadiene with ethylene, acrylonitrile, vinyl chloride, vinyl alcohol, acetylene, cyanoacetylene, and dicyanoacetylene have been located with ab initio molecular orbital calculations and the 3-21G basis set; the activation energies were also evaluated by single-point calculations at the RHF/6-31G* and MP2/6-31G* theory levels on the 3-21G geometries. The activation energies and asynchronicities of these reactions follow the same trends as the corresponding reactions of butadiene with alkenes and alkynes. The effect of the aza group in the diene is very small. The influence of a Lewis acid complexed to the 2-azabutadiene was also studied.