期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 19, 期 45, 页码 15304-15314出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201302079
关键词
alkynes; carbenes; CC coupling; dimerization; rhodium
资金
- Spanish Ministerio de Economia y Competitividad (MEC/FEDER) [CTQ2010-15221, CTQ2012-35665]
- Diputacion General de Aragon [E07]
- ARAID Foundation
- CONSOLIDER INGENIO under the Project MULTICAT [CSD2009-00050]
- CONACyT (Mexico) [186898]
A general regioselective rhodium-catalyzed head-to-tail dimerization of terminal alkynes is presented. The presence of a pyridine ligand (py) in a Rh-N-heterocyclic-carbene (NHC) catalytic system not only dramatically switches the chemoselectivity from alkyne cyclotrimerization to dimerization but also enhances the catalytic activity. Several intermediates have been detected in the catalytic process, including the -alkyne-coordinated Rh-I species [RhCl(NHC)((2)-HCCCH2Ph)(py)] (3) and [RhCl(NHC){(2)-C(tBu)C(E)CHCHtBu}(py)] (4) and the Rh-III-hydride-alkynyl species [RhClH{CCSi(Me)(3)}(IPr)(py)(2)] (5). Computational DFT studies reveal an operational mechanism consisting of sequential alkyne CH oxidative addition, alkyne insertion, and reductive elimination. A 2,1-hydrometalation of the alkyne is the more favorable pathway in accordance with a head-to-tail selectivity.
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