Density functional theory study of ethene and acetylene addition to oxazole and protonated oxazole

Abstract

The suitability of the electron deficient oxazole for an inverse Diets–Alder reaction is presented. The qualitative reactivities have traditionally been evaluated by using the frontier molecular orbital (FMO) energy gaps between the reactants. The transition-state structures for the reaction of oxazole and protonated oxazole with ethene, acetylene and their methyl derivatives have been calculated with ab initio, DFT and AM1 semiempirical methods and their results were compared and discussed. A new approach, Becke3LYP/6-31 + G*//AM1 for obtaining activation energies has been introduced and compared with the traditional calculations.