Triplex Diels-Alder reactions of beta-methylstyrenes. Density functional investigation of pion-pion interactions
Hartsough, David Scott
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https://hdl.handle.net/2142/19435
Description
Title
Triplex Diels-Alder reactions of beta-methylstyrenes. Density functional investigation of pion-pion interactions
Author(s)
Hartsough, David Scott
Issue Date
1991
Doctoral Committee Chair(s)
Schuster, Gary B.
Department of Study
Chemistry, Organic
Discipline
Chemistry, Organic
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Language
eng
Abstract
The (4+2) cycloaddition of an electron-rich diene to an electron-rich dienophile may be catalyzed by irradiation of a cyanoarene. This reaction is shown to proceed through an intermediate ternary excited state complex (triplex) and is therefore called the triplex Diels-Alder reaction. Evidence is presented demonstrating the ability of this process to catalyze the additions of acyclic dienophiles to a cyclic diene. Furthermore, this reaction is found to occur with a high degree of syn stereospecificity.
Local density functional theory as implemented in the program DMol is examined as a method for the evaluation of interactions between $\pi$-electron containing molecules. For the evalution of interactions between acetylene and various substituted acetylenes DMol is found to correlate quite well with MP2 calculations using a 6-31G* basis set. DMol is then used to evaluate the interactions between larger $\pi$-electron containing molecules (benzene and substituted benzenes). It is found for eclipsed binary aromatic complexes that a positive correlation exists between the energetic bias favoring the edge-face over the face-face form of the complex and the electron richness of one of the members of the complex. Conversely, it is found that the presence of an electron deficient member lowers the energetic bias favoring the edge-face form of the complex. Additionally, there is a large driving force for sliding the rings apart from the eclipsed geometry in face-face complexes containing an electron rich member. In complexes containing an electron deficient member this driving force is much less. These observations can best be understood on the basis of the electrostatic interactions between the $\pi$-electron systems.
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