- 作者: 蘇明德
- 作者服務機構: School of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 80708, Taiwan, R.O.C.
- 中文摘要: The potential energy surfaces for the cycloaddition reactions of angle strained cycloalkynes to ethylene have been studied using ab initio methods. All the stationary points were determined with the MP2/6-311G(d,p) method with some calculations performed at the CCSD(T)/6-311G++G(d,p)//MP2/6-311G(d,p) level. Three kinds of cycloalkyne species, including monocyclic alkynes, bridged bicyclic alkynes, and heterocyclic alkynes, have been chosen in this work as model reactants. Two different reaction pathways have been proposed: (A) 1,2-carbon shift and (B) 1,2-hydrogen shift. That is, reactants R [2+1]-TS-1 R spirocarbene intermediate R (A) TS-A R Pro-A or (B) TS-B R Pro-B. As a result, it is found that ground-state cycloalkyne appears to react more like a monocarbene than like an alkyne or a vicinal dicarbene as conventionally proposed. Our theoretical investigations also suggest that a cycloalkyne with a small C-CoC bond angle should be a good candidate for cycloaddition to an olefin. Moreover, in the cycloaddition reaction of a small (£ six-membered ring six-membered) ring cycloalkyne, both 1,2-carbon and 1,2-hydrogen migrations will compete with each other. On the other hand, reactions involving larger (3 seven-membered) ring cycloalkynes should proceed with a 1,2-carbon shift, leading to the major [2+2] cycloadduct. Furthermore, a configuration mixing model has been used to rationalize the computational results and to develop an explanation for the barrier heights. The results obtained allow a number of predictions to be made.
- 英文摘要: --
- 中文關鍵字: Cycloaddition reactions; Cycloalkynes; Configuration mixing model.
- 英文關鍵字: --