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  • Title: C-C alpha insertion: insertion of an alkyne into the C-C single bond between the carbene-carbon atom and the alpha-carbon atom of a Fischer carbene complex by an unprecedented metalla(di-pi-methane) skeletal rearrangement.
    Author: Unaldi S, Aumann R, Fröhlich R.
    Journal: Chemistry; 2003 Jul 21; 9(14):3300-9. PubMed ID: 12866074.
    Abstract:
    The first examples of insertion of a C(triple bond)C bond of an alkyne into a C(carbene)-Calpha single bond of a carbene complex (C-Calpha insertion) are reported. (prim-Alkyl)carbene complexes [(OC)(5)M=C(OEt)CH(2)R] (1 a-f; M=Cr, W; R=nPr, C(7)H(7), Ph) undergo C-Calpha insertion of electron-deficient alkynes [PhC(triple bond)CC(XEt)NMe(2)]BF(4) (5 a,b; X=O, S) to give zwitterionic carbiminium carbonylmetalates 3 a-g, which are thermally transformed into (CO)(4)M chelate carbene complexes 4 a-g by elimination of CO. The overall reaction is highly regio- and stereoselective. It involves an unprecedented metalla(di-pi-methane) rearrangement as the key step.
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