Synthesis of (Allyloxy)(alkynyl)carbene Complexes and Their Reaction with Octacarbonyldicobalt: An Unprecedented Retro-Fischer Reaction

Synthesis and reactivity of metal carbene complexes with heterobiaryl spacer substituents

“…Dilithiated bithiophene was reacted with the metal hexacarbonyl at low temperature and alkylation of the intermediated products with methyl trifluoromethanesulfonate affording the mono-and biscarbene complexes (1-4) as well as complexes where alkylation proceeded via ring opening of tetrahydrofuran (6)(7)(8). D ötz and co-workers 25 were the first to observe an opening of the THF ring during alkylation of Fischer carbene complexes with magic methyl. Raubenheimer and co-workers reported the formation of similar compounds during the alkylation of carbene complexes containing an azolyl organic substituent.…”

μ-Furan-2,5-diylbis(methoxycarbene)-bis[pentacarbonylchromium(0)]

“…The title compound was isolated as the main product from the reaction of dilithiated furan (Chadwick & Willbe, 1977) and two equivalents of hexacarbonylchromium (Crause et al, 2005) and subsequent alkylation with six equivalents of methyl trifluoromethanesufonate (Christoffers & Dö tz, 1994). The title compound was purified and isolated as a purple band from a silica-gel 60 column using a 2:1 mixture of hexane and dichloromethane as eluant.…”

“…This intermediate, (1), may influence the orientation of carbene substituents in the final product. If the intermediate displays interactions between the lithium cations and the O atoms of the acylate and furan groups, methylation (Christoffers & Dö tz, 1994), in the third step, will be determined by the rigid structure resulting from the interactions of the ions. Hence, one would predict that the methoxy substituent would adopt a cis position about the C(carbene)-C(furan) bond with respect to the furan O atom, and, with little rotation around the C(carbene)-O bond, the methyl group should be trans to the furan ring.…”

Unexpected Reaction Pathways in the Reaction of Alkoxyalkynylchromium(0) Carbenes with Aromatic Dinucleophiles

“…In spite of the number of reactions reported for α , β ‐unsaturated Fischer carbene complexes,8 reactions in which a fragmentation of the carbon skeleton is involved are rare. At the beginning of this work, only one example of this kind of process had been described 9a. Thus, Dötz and co‐workers reported the spontaneous retro‐Fischer fragmentation of complex 4 to form enyne 5 (Scheme ).…”