Tandem [4+2]/retro[3+2]/[3+2] cycloaddition reactions of fluorinated-oxadiazoles with conjugated, unconjugated, cyclic, and acyclic dienes

IF 1.9 4区 化学 Q2 CHEMISTRY, ORGANIC
Joshua Atta-Kumi, George Baffour Pipim, Ernest Opoku
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引用次数: 0

Abstract

The tandem reactions of 2,5-bis(trifluoromethyl)-1,3,4-oxadiazole with conjugated, unconjugated, acyclic, and cyclic dienes have been studied at the M06-2X/6-311++G(d,p) level of theory. The rate-determining step is the initial [4+2] cycloaddition in the tandem reaction of 2,5-bis(trifluoromethyl)-1,3,4-oxadiazole with acyclic, cyclic, conjugated, and unconjugated dienes, whereas the stereochemistry of the tandem adduct is determined by the [3+2] step. The exo-coupling is kinetically favored over the endo-coupling in the initial [4+2] reaction of 2,5-(bis-trifluoromethyl)-1,3,4-oxadiazole with all the considered dienes. In the retro [3+2] step (N2 extrusion), higher activation energy is required to furnish the carbonyl ylide in the reaction of 2,5-(bis-trifluoromethyl)-1,3,4-oxadiazole with conjugated and unconjugated cyclic dienes as compared with the reaction with unconjugated acyclic dienes. At the stereochemistry [3+2] step, the intermolecular addition is kinetically favored over the intramolecular addition in the [3+2] reaction of 2,5-(bis-trifluoromethyl)-1,3,4-oxadiazole with both conjugated or unconjugated cyclic dienes and unconjugated acyclic dienes. The reaction proceeds with low activation energies when conjugated and unconjugated cyclic dienes are participating, compared with those of unconjugated acyclic dienes. Overall, the tandem process proceeds via an asynchronous one-step mechanism [4+2] coupling in an exo- or endo-cycloaddition fashion, followed by a retro [3+2], which extrudes the N2, and then the stereo-determining intermolecular or intramolecular [3+2] cycloaddition step, which leads to the tandem products. The polarity of both inter- and intra-molecular cycloaddition steps can be influenced by two factors: the nature of the heteroatom present on the diene molecule and the size of the cyclic diene. These factors play a role in determining the reactivity and electron distribution within the diene, thereby impacting the overall polarity of the cycloaddition reactions.

Abstract Image

Abstract Image

氟化噁二唑与共轭、非共轭、环状和非环状二烯的串联[4+2]/反式[3+2]/[3+2]环加成反应
在 M06-2X/6-311++G(d,p) 理论水平上研究了 2,5-双(三氟甲基)-1,3,4-恶二唑与共轭、非共轭、无环和环状二烯的串联反应。在 2,5-双(三氟甲基)-1,3,4-恶二唑与无环、环、共轭和非共轭二烯的串联反应中,决定速率的步骤是最初的[4+2]环加成反应,而串联加合物的立体化学结构则由[3+2]步骤决定。在 2,5-(双三氟甲基)-1,3,4-恶二唑与所有二烯的初始[4+2]反应中,外偶联在动力学上优于内偶联。在复[3+2]步骤(N2 挤压)中,2,5-(双三氟甲基)-1,3,4-恶二唑与共轭和非共轭环状二烯的反应比与非共轭无环二烯的反应需要更高的活化能来生成羰基酰亚胺。在立体化学[3+2]步骤中,2,5-(双三氟甲基)-1,3,4-恶二唑与共轭或未共轭环状二烯和未共轭无环二烯的[3+2]反应中,分子间加成在动力学上比分子内加成更有利。与非共轭无环二烯的活化能相比,共轭和非共轭环状二烯参与反应时的活化能较低。总的来说,串联过程通过非同步的一步机制[4+2]偶联以外向或内向环加成的方式进行,然后是逆向[3+2],挤出 N2,然后是立体决定性的分子间或分子内[3+2]环加成步骤,最终得到串联产物。分子间和分子内环加步骤的极性受两个因素的影响:二烯分子上存在的杂原子的性质和环二烯的大小。这些因素在决定二烯内部的反应性和电子分布方面发挥着作用,从而影响环化反应的整体极性。
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来源期刊
CiteScore
3.60
自引率
11.10%
发文量
161
审稿时长
2.3 months
期刊介绍: The Journal of Physical Organic Chemistry is the foremost international journal devoted to the relationship between molecular structure and chemical reactivity in organic systems. It publishes Research Articles, Reviews and Mini Reviews based on research striving to understand the principles governing chemical structures in relation to activity and transformation with physical and mathematical rigor, using results derived from experimental and computational methods. Physical Organic Chemistry is a central and fundamental field with multiple applications in fields such as molecular recognition, supramolecular chemistry, catalysis, photochemistry, biological and material sciences, nanotechnology and surface science.
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