The Mechanism of the Catalytic Functionalization of Haloalkanes by Carbene Insertion: An Experimental and Theoretical Study
2009; American Chemical Society; Volume: 28; Issue: 20 Linguagem: Inglês
10.1021/om9006888
ISSN1520-6041
AutoresJuan Urbano, Ataualpa Albert Carmo Braga, Feliu Maseras, Eleuterio Álvarez, M. Mar Díaz‐Requejo, Pedro J. Pérez,
Tópico(s)N-Heterocyclic Carbenes in Organic and Inorganic Chemistry
ResumoCarbon−halogen (C−X) bonds (X = Cl, Br) can be easily functionalized with ethyl diazoacetate (N2CHCO2Et) in the presence of silver-based catalysts containing the TpxAg core (Tpx = hydrotrispyrazolylborate ligand). Polyhalomethanes are converted into products derived from the formal insertion of the carbene CHCO2Et units into the C−X bond. In the case of monohaloalkanes (C4−C6), cleavage of the C−X bond is observed, with formation of XCH2CO2Et and the corresponding olefin. Experimental evidence and theoretical calculations have led to the proposal of a novel mechanism to account for these transformations, in which the metal participates along the pathway in all the reaction steps. Among the experimental data, the first example of a metal-induced, asymmetric functionalization of a C−Cl bond by carbene insertion is included (ee = 14 ± 2%).
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