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On the Catalytic Effect of Water in the Intramolecular Diels–Alder Reaction of Quinone Systems: A Theoretical Study
Departamento de Química, Facultad de Ciencias, Universidad de Chile, Santiago, Casilla 653, Chile
Departamento de Química, Universidad Técnica Federico Santa María, Valparaíso, Casilla 110-V, Chile
Departamento de Química Orgánica, Universidad de Valencia, 46100, Valencia, Spain
* Authors to whom correspondence should be addressed.
Received: 18 September 2012; in revised form: 8 November 2012 / Accepted: 12 November 2012 / Published: 20 November 2012
Abstract: The mechanism of the intramolecular Diels–Alder (IMDA) reaction of benzoquinone 1, in the absence and in the presence of three water molecules, 1w, has been studied by means of density functional theory (DFT) methods, using the M05-2X and B3LYP functionals for exploration of the potential energy surface (PES). The energy and geometrical results obtained are complemented with a population analysis using the NBO method, and an analysis based on the global, local and group electrophilicity and nucleophilicity indices. Both implicit and explicit solvation emphasize the increase of the polarity of the reaction and the reduction of activation free energies associated with the transition states (TSs) of this IMDA process. These results are reinforced by the analysis of the reactivity indices derived from the conceptual DFT, which show that the increase of the electrophilicity of the quinone framework by the hydrogen-bond formation correctly explains the high polar character of this intramolecular process. Large polarization at the TSs promoted by hydrogen-bonds and implicit solvation by water together with a high electrophilicity-nucleophilicity difference consistently explains the catalytic effects of water molecules.
Keywords: intramolecular Diels–Alder reactions; polar Diels–Alder reactions; water catalysis; DFT reactivity indices; local reactivity difference index
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Soto-Delgado, J.; Aizman, A.; Contreras, R.; Domingo, L.R. On the Catalytic Effect of Water in the Intramolecular Diels–Alder Reaction of Quinone Systems: A Theoretical Study. Molecules 2012, 17, 13687-13703.
Soto-Delgado J, Aizman A, Contreras R, Domingo LR. On the Catalytic Effect of Water in the Intramolecular Diels–Alder Reaction of Quinone Systems: A Theoretical Study. Molecules. 2012; 17(11):13687-13703.
Soto-Delgado, Jorge; Aizman, Arie; Contreras, Renato; Domingo, Luis R. 2012. "On the Catalytic Effect of Water in the Intramolecular Diels–Alder Reaction of Quinone Systems: A Theoretical Study." Molecules 17, no. 11: 13687-13703.