Reaction Mechanism of Polar Diels-Alder Reactions Between 3-Nitrofuran and different Dienes. A Theoretical Study

The reactivity in Polar Diels-Alder reactions of 3-nitrofuran acting as electrophile join to several dienes of different nucleophilicity is analyzed using computational theorical methods based in the DFT theory. Electrophilicity and nucleophilicity indices, based in the energy of frontier molecular orbitals, were the parameters employed. It was observed that the pentaheterocycle suffer the cycloaddition yielding benzofuran derivatives. The regioselectivity was predicted using Fukui function and the reaction mechanism was analyzed. It was observed that there is only one asymmetric and asynchronous transition state between the reactants and the primary cycloadduct when isoprene is the diene involved, and two transition states when 1-methoxy-1,3-butadiene and Danishefsky's diene were used. The last observation is not common in this cycloaddition reactions and it would be based in the polar character that increase with the nucleophilicity of the dienes.