A Density Functional Theory Study on the Diels-Alder Reactions with Vinylallenes as Dienes

The Diels-Alder (DA) reactions of vinylallenes (VA) with ethylenes were investigated using the global electrophilicity and nucleophilicity of the corresponding reactants as global reactivity indexes defined within the conceptual density functional theory. The reactivity and regioselectivity of these reactions were predicted by analysis of the energies, geometries, and electronic nature of the transition-state structures. In general, substitution by the electron-accepting acetyl group favors the reaction, whereas substitution by the electron-releasing methoxy group provides the opposite effect, regardless of being on VA or ethylene. However, the substitution effect in ethylene is apparently greater than that in VA. It has also been disclosed that substitution by electron-accepting group on both reactants accelerates the reaction, and the reaction may give different regioselectivity from that between VA and acetylsubstituted ethylene. This has also been verified by our experiments. It seems that the DA reactions with VAs as the diene components can generally be classified as nonpolar asynchronous with the endo product formation (wherever possible) being more pronounced. (C) 2010 Wiley Periodicals, Inc. Int J Quantum Chem 111: 3805-3815, 2011