Carbon—hydrogen bonds metal carbene synthesis

Isocyanide insertion reactions into heteroatom—hydrogen, carbon-halogen, carbon—hydrogen bonds, and metal carbenes 13CSR5257. Last advances in synthesis of added value compounds and materials by laccase-mediated biocatalysis 12COC2508. 

Pertinent reviews published during 1980 cover cyclometallation of P-donor ligands, CO insertion into metal-carbon o-bonds, mechanistic features of catalytic CO hydrogenation reactions, and stoicheiometric reactions of transition-metal carbene complexes. Other articles of interest deal with the stability of metal-carbon bonds, " transition-state geometry for insertion of metals into C-H bonds, organic synthesis using Group VIII metal complexes, and C-H bond activation by transition metals. " Molecular orbital calculations on the interconversion of metal bis(olefin) and metallocyclo-pentane complexes have been reported. ... 

A further approach to the synthesis of pyrroles other than that shown in Scheme 47 involves formation of l-metalla-5-aza-l,3,5-trienes 123 (M = W) by insertion of an alkyne into the M=C bond of an (imino)carbene complex 121, leading to chain extension by two carbon atoms ( alkyne route to pyrroles). Compounds 123 cyclize spontaneously to 2//-pyrrole complexes 124, from which ///-pyrroles 122 are obtained by disengagement of the metal unit (Scheme 48).l2d 2H-Pyrrole complexes of type 124 have been characterized by X-ray analysis, and 2/Z-pyrroles could be eliminated from such complexes if substituents other than hydrogen are attached to C2 of the compound.136125 137 l2al2b... 

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