AM1 study of catalytic hydrogenation of 3-anilinomethylidene-6-aryl-5,6-2H-dihydropyran-2,4-diones

3-(p-methyl)anilinomethylidene-6-aryl-5,6-2H-dihydropyran-2,4-dione was sel ected as the model reactant compound to study the catalytic hydrogenation o f 3-anilinomethylidene-6-aryl-5,6-2H-dihydropyran-2,4-diones by the AMI sem i-empirical method. Molecular information such as net charges, bond orders, values of frontier orbital energies, composition, proportions and bonding contribution was acquired and analyzed. Thus, possible reactive sites were proposed and the reaction mechanism was postulated via two different pathwa ys. The postulated intermediates and products were also computed using the AM1 method. Their heat of formation values and energies of HOMO/LUMO/SOMO i ndicate that the mechanism of catalytic hydrogenation of 3-anilinomethylide ne-6-aryl-5,6-2H-dihydropyran-2,4-diones is hydrogenolytic cleavage on a di hydropyrandione ring, not the simple addition of a C=C double bond. Therefo re, the experiment result is elucidated theoretically. (C) 2000 Elsevier Sc ience B.V. All rights reserved.