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- [1] Taming the 1,5-sigmatropic shift across protonated spirocyclic 4H-pyrazolesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, 2024, 37 (09)Levandowski, Brian J.Graham, Brian J.Abularrage, Nile S.Raines, Ronald T.
Probative Evidence and Quantitative Energetics for the Unimolecular Mechanism of the 1,5-Sigmatropic Hydrogen Shift of Cyclopentadiene
被引：5
|作者：
Tran, Quan
[1
]
Sengupta, Arkajyoti
[1
]
Houk, K. N.
[1
]
机构：
[1] Univ Calif Los Angeles, Dept Chem & Biochem, Los Angeles, CA 90095 USA
基金：
美国国家科学基金会;
关键词：
DENSITY-FUNCTIONAL THEORY;
DIELS-ALDER REACTIONS;
PERICYCLIC-REACTIONS;
1,5-HYDROGEN SHIFT;
COUPLED-CLUSTER;
AB-INITIO;
ENERGIES;
KINETICS;
STATE;
THERMOCHEMISTRY;
D O I：
10.1021/acs.joc.2c02145
中图分类号：
O62 [有机化学];
学科分类号：
070303 ;
081704 ;
摘要：
While the 1,5-sigmatropic hydrogen shift in cyclopentadiene is generally thought to be a unimolecular pericyclic reaction, Yamabe proposed a more complex bimolecular mechanism proceeding through the exo dimer of cyclopentadiene. DFT computations by Yamabe were claimed to show that the bimolecular mechanism was kinetically more favorable than the unimolecular mechanism. Reinvestigation of the unimolecular concerted mechanism and Yamabe's bimolecular mechanism with omega B97X-D and DLPNO-CCSD(T) calculations demonstrates a 25 kcal/mol preference for the unimolecular mechanism relative to the bimolecular mechanism. While Yamabe's calculations were performed with the less accurate B3LYP functional, the incorrect conclusion was the result of a different error discovered here. We have also computed corrections for tunneling that result in computed activation barriers within 1.5 kcal/mol of the experimental values.
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页码：14995 / 15000
页数：6
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