Lewis Acid and Substituent Effects on the Molecular Mechanism for the Nazarov Reaction of Penta-1,4-dien-3-one and Derivatives. A Topological Analysis Based on the Combined Use of Electron Localizatio
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- 作者：Victor Polo ; Juan André ; s
- 刊名：Journal of Chemical Theory and Computation
- 出版年：2007
- 出版时间：May 2007
- 年：2007
- 卷：3
- 期：3
- 页码：816 - 823
- 全文大小：157K
- 年卷期：v.3,no.3(May 2007)
- ISSN：1549-9626
文摘
The joint use of the topological analysis provided by the electron localization function(ELF) and catastrophe theory (CT), at the B3LYP/6-31G(d) calculation level, allows us to examinethe Lewis acid (protonation H+ and presence of BH3) and the role of an electron donor substituent(-OCH3) at 
and 
positions along the course of the molecular mechanism for the Nazarovrearrangement of penta-1,4-dien-3-one and eight derivatives. The progress of the reaction ismonitored by the changes of the ELF structural stability domains (SSDs), each change beingcontrolled by a turning point derived from CT. These SSDs and the corresponding turning pointsare associated with a sequence of elementary chemical steps. Along the cyclization path ofpenta-1,4-diene-3-one, four SSDs as well as three turning points (cusp1-fold1-cusp2) havebeen characterized. The first and second SSDs correspond to a polarization of the C-O bondand electronic redistribution among the C-C bonds, respectively, and they can be associatedwith the formation of an oxyallyl structure. The third and fourth SSDs can be assigned to thering closure process. Protonation of the oxygen atom shifts the reactive directly into the secondSSD, greatly reducing the activation and reaction energies. The electronic effects due to Lewisacids and electron donor substituents have been rationalized in terms of calculations ofmesomeric structures from ELF basin populations. The combination of Lewis acids togetherwith and -OCH3 substitutions renders a cooperative and competitive effect on activationand reaction free energies, respectively.
and positions along the course of the molecular mechanism for the Nazarovrearrangement of penta-1,4-dien-3-one and eight derivatives. The progress of the reaction ismonitored by the changes of the ELF structural stability domains (SSDs), each change beingcontrolled by a turning point derived from CT. These SSDs and the corresponding turning pointsare associated with a sequence of elementary chemical steps. Along the cyclization path ofpenta-1,4-diene-3-one, four SSDs as well as three turning points (cusp1-fold1-cusp2) havebeen characterized. The first and second SSDs correspond to a polarization of the C-O bondand electronic redistribution among the C-C bonds, respectively, and they can be associatedwith the formation of an oxyallyl structure. The third and fourth SSDs can be assigned to thering closure process. Protonation of the oxygen atom shifts the reactive directly into the secondSSD, greatly reducing the activation and reaction energies. The electronic effects due to Lewisacids and electron donor substituents have been rationalized in terms of calculations ofmesomeric structures from ELF basin populations. The combination of Lewis acids togetherwith and -OCH3 substitutions renders a cooperative and competitive effect on activationand reaction free energies, respectively.