An AM1 calculational study of the DielsAlder addition of maleic anhydride to C5-substituted pentamethylcyclopentadienes and 2,5-dimethylthiophene oxide. An attempt to ascertain the factors controlling the -facial selectivities and relative reactivities

The Diels–Alder reactions of maleic anhydride (1) with a group of C5-substituted cyclopentadienes and 2,5-dimethylthiophene oxide (5) have been studied with the semi-empirical method AM1. We find that the facial selectivities and relative reactivities found experimentally for six dienes (2a–2f) are accurately reproduced at this level of theory. The results of the calculational study provide no concrete support for the proposal that σ–σ* …