Rhodium(I)-N-Heterocyclic Carbene Catalyst for Selective Coupling of N-Vinylpyrazoles with Alkynes via C鈥揌 Activation

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• 作者：Ram贸n Azp铆roz ; Laura Rubio-P茅rez ; Andrea Di Giuseppe ; Vincenzo Passarelli ; Fernando J. Lahoz ; Ricardo Castarlenas ; Jes煤s J. P茅rez-Torrente ; Luis A. Oro
• 刊名：ACS Catalysis
• 出版年：2014
• 出版时间：December 5, 2014
• 年：2014
• 卷：4
• 期：12
• 页码：4244-4253
• 全文大小：501K
• ISSN：2155-5435

文摘

The complex [Rh(渭-Cl)(IPr)(畏²-coe)]₂ {IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-carbene, coe = cis-cyclooctene} efficiently catalyzes the coupling of alkynes and N-vinylpyrazole via C鈥揌 activation, leading to Markovnikov-selective butadienylpyrazole derivatives under mild conditions. A straightforward approach to cross-conjugated acyclic trienes is also operative through a one-pot alkyne dimerization-hydrovinylation tandem reaction. The proposed mechanism involves C鈥揌 activation of vinylpyrazole directed by nitrogen coordination to the metallic center. Subsequent alkyne coordination, insertion, and reductive elimination steps lead to the coupling products. Several key intermediates participating in the catalytic cycle have been detected and characterized, including a 魏-N, 畏²-C鈺怌 coordinated vinylpyrazole complex and a Rh^III-hydride-alkenyl species resulting from the C鈥揌 activation of the vinylpyrazole

Keywords:

C鈭扝 activation; C鈭扖 coupling; pyrazole; N-heterocyclic carbene; rhodium