Regio- and stereoselectivity in the Diels-Alder reaction of vinylallenes with acrolein: an ab initio study

by Wright, Jeffery B.; Pranata, Julianto

To explore the regio- and stereoselectivity in Diets-Alder reactions of vinylallenes with acrolein, a parent vinylallene/acrolein system and a methyl-substituted vinylallene/acrolein system were studied. Ab initio calculations were used to identify eight transition state structures for each of the two Diels-Alder reactions at various computational levels (RHF/6-31G(d), RHF/6-311G(2d), B3LYP/6-311G(2d), and MP2/6-311G(2d)). The relative energies of the endo and exo transition states along with the regioselectivity have been determined from these calculations. In the parent vinylallene/acrolein system, the endo s-cis transition structure is the preferred stereoselectivity at all levels of theory, however, there is no regioselectivity. In the methyl substituted vinylallene/acrolein system, the endo s-trans transition state tends to compete with the endo s-cis transition state at the RHF levels of theory and is 1 kcal/mol more stable at the B3LYP/6-311G(2d) level of theory. Also, in the methyl-substituted system, there is now a definite preference for one regioisomer over the other. Both Diels-Alder reaction systems are asynchronous with the methyl-substituted system being more pronounced. (C) 1999 Elsevier Science B.V. All rights reserved.

Journal
Journal of Molecular Structure-Theochem
Volume
460
Issue
1-3
Year
1999
Start Page
67
ISBN/ISSN
2210-2728; 0166-1280
DOI
10.1016/S0166-1280(98)00307-8