DFT Study of the Mechanism and Regioselectivity of 1,3-Pentadiene with Methyl Acrylate Using Theoretical Approaches

Ab initio density functional theory (DFT) calculations have been used to study regioselectivity in the Diels-Alder (DA) cycloaddition reaction between 1,3-pentadiene and methyl acrylate. The DFT calculations were performed with the B3LYP functional and 6-311+G~(**) basis set. Two synchronous transition structures corresponding to the formation of different regioisomers associated with the two reaction channels have been located. The DFT calculations generated transition geometries with a very small degree of asynchronicity. The present analysis shows that these reactions have normal electron demand (NED) character. Moreover, the results obtained from energetic and electronic approaches with the exception of Houk’s rule confirm that ortho regioisomer is the major product.