Theoretical studies of the Diels-Alder reaction of 1-fluoroethylene with some model dienes

3-Vinylcoumarin and 3-trifluorovinylcoumarin have been chosen as model compounds for [4+2]-cycloaddition reaction. Density functional theory (DFT) has been applied to the study of concerted mechanism of the Diels-Alder reaction with fluorinated ethylene. The main goal of this work was to determine the transition state (TS) on several concerted paths of reaction to examine the reposelectivity of the Diels-Alder reaction in our model systems. The effect of fluorine substitution on TS fortriation has been estimated. Theoretical investigation has led to the conclusion. that the introduction of one electron-withdrawing substituent (fluorine atom) into dienophile molecule makes the process of reaching the TS more difficult due to an increase in the 'energy of concert' (DeltaG(act)(0)) compared to non-fluorinated system. The substitution of fluorine for hydrogen in exocyclic vinyl group results (with one exception) in a lower activation energy and higher energy gain of reaction for systems with 1-fluoroethylene. (C) 2004 Published by Elsevier B.V.