Rhodium(I)-N-heterocyclic carbene catalyst for selective coupling of N-vinylpyrazoles with alkynes via C-H activation
The complex [Rh(μ-Cl)(IPr)(η2-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–H activation, leading to Markovnikov-selective butadienylpyrazole derivatives under mild conditions. A straight...
| Autores: | , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión aceptada para publicación |
| Fecha de publicación: | 2014 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/133820 |
| Acceso en línea: | http://hdl.handle.net/10261/133820 |
| Access Level: | acceso abierto |
| Palabra clave: | C−H activation C−C coupling N-heterocyclic carbene Pyrazole Rhodium |
| Sumario: | The complex [Rh(μ-Cl)(IPr)(η2-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–H 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–H 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 κ-N, η2-C═C coordinated vinylpyrazole complex and a RhIII-hydride-alkenyl species resulting from the C–H activation of the vinylpyrazole. |
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