Combined experimental and computational investigations of rhodium-catalysed C - H functionalisation of pyrazoles with alkenes.
Combined experimental and computational investigations of rhodium-catalysed C - H functionalisation of pyrazoles with alkenes.
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DOI：
10.1002/chem.201405550
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发表时间：
2015-02-09
期刊：
影响因子：
--
通讯作者：
Villa-Marcos B
中科院分区：
文献类型：
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作者：
Algarra AG;Davies DL;Khamker Q;Macgregor SA;McMullin CL;Singh K;Villa-Marcos B
采用[Rh(MeCN)3Cp*][PF6]2/Cu(OAc)2⋅H2O催化剂体系，对烯烃C2H3Y (Y=CO2Me (a), Ph (b)， C（O)Me (C)）与3-芳基-5-R-吡唑(R=Me (1a), Ph （1b), CF3 (1c)）的氧化偶联进行了详细的实验和计算研究。在丙烯酸甲酯与丙烯酸甲酯的反应中，形成了多达5种产物（2aa - 6aa），包括反式单乙烯基产物（在新型CuI二聚体（2aa）内络合或作为自由种（3aa））和二乙烯基种（6aa）；3aa和6aa经过aza-Michael反应环化，分别得到4aa和5aa的杂环。对于苯乙烯，只观察到反式单酰化和二酰化产物，而对于甲基乙烯酮，一个更强的迈克尔受体，只形成环化的氧化偶联产物。采用密度泛函理论计算表征了1a与丙烯酸甲酯和苯乙烯反应中不同的迁移插入和β-H转移步骤。计算结果表明，2,1插入和反式乙烯基产物的形成具有明显的动力学偏好，与实验结果一致。
Detailed experimental and computational studies have been carried out on the oxidative coupling of the alkenes C2H3Y (Y=CO2Me (a), Ph (b), C(O)Me (c)) with 3-aryl-5-R-pyrazoles (R=Me (1 a), Ph (1 b), CF3 (1 c)) using a [Rh(MeCN)3Cp*][PF6]2/Cu(OAc)2⋅H2O catalyst system. In the reaction of methyl acrylate with 1 a, up to five products (2 aa–6 aa) were formed, including the trans monovinyl product, either complexed within a novel CuI dimer (2 aa) or as the free species (3 aa), and a divinyl species (6 aa); both 3 aa and 6 aa underwent cyclisation by an aza-Michael reaction to give fused heterocycles 4 aa and 5 aa, respectively. With styrene, only trans mono- and divinylation products were observed, whereas with methyl vinyl ketone, a stronger Michael acceptor, only cyclised oxidative coupling products were formed. Density functional theory calculations were performed to characterise the different migratory insertion and β-H transfer steps implicated in the reactions of 1 a with methyl acrylate and styrene. The calculations showed a clear kinetic preference for 2,1-insertion and the formation of trans vinyl products, consistent with the experimental results.