AB-INITIO STUDY OF THE LOW REACTIVITY OF THIOPHENE IN DIELS-ALDER REACTIONS WITH CARBON DIENOPHILES

The utility of thiophene as a diene for Diels-Alder reactions was stud ied by ab initio methods, The reactivity was evaluated with three dien ophiles, vinyl alcohol, ethylene and acrylonitrile, Qualitatively the reactivity was determined by comparison of the reactant's frontier orb ital energies, bond orders and charge transfer in the transition state s, Quantitatively the reactivity was determined by estimation of activ ation energy with RHF/6-31G, MP2/6-31G*, MP3/6-31G*parallel to MP2/6- 31G and MP4/6-31G parallel to MP2/6-31G* ab initio calculations. The results of the calculations predicts that the reactivity of thiophene with acrylonitrile is similar to butadiene and ethylene with a preferr ed formation of the endo isomer.