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Spin-Coupled Study of the Electronic Mechanism of the Hetero-Diels−Alder Reaction of Acrolein and Ethene

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journal contribution
posted on 13.01.2005, 00:00 by Joshua J. Blavins, David L. Cooper, Peter B. Karadakov
Modern valence bond theory, in its spin coupled form, is used to elucidate the electronic rearrangements that take place during the course of the gas-phase hetero-Diels−Alder cycloaddition reaction of s-cis-acrolein (cis-1-oxabutadiene or cis-propeneal) and ethene. It is found that the most dramatic changes to the electronic structure occur in a relatively narrow interval of the reaction pathway soon after the transition state and that the system passes through a geometry at which it can be considered to be significantly aromatic. Although concerted, the reaction is markedly asynchronous, with the breaking of the carbon−oxygen π bond, and the formation of the new carbon−oxygen σ bond, “lagging behind” somewhat the other bond-making and bond-breaking processes.