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Carbene insertion reactions ruthenium

An unprecedented carbene insertion reaction was observed on reaction of the cationic re-arene ruthenium amidinates with trimethylsilyldiazo-methane (Scheme 145, TFPB = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate). [Pg.281]

The catalytic production of olefins, diethyl maleate and fumarate, from ethyl diazoacetate has been reported with osmium [ 149] and ruthenium [ 128] porphyrins. Despite the periodic relationship of ruthenium to iron and osmium and the syntheses of different carbene complexes of ruthenium porphyrins, developed by Collman et al. [125-127], it is only very recently that cyclopropanation [135,171] and ethyl diazoacetate insertion into heteroatom bond reactions [172] were observed using ruthenium porphyrins as catalysts. The details of the catalytic reaction of diazo esters with simple olefins catalyzed with ruthenium porphyrins have been reported [173]. Product yields. [Pg.110]

While major advances in the area of C-H functionalization have been made with catalysts based on rare and expensive transition metals such as rhodium, palladium, ruthenium, and iridium [7], increasing interest in the sustainability aspect of catalysis has stimulated researchers toward the development of alternative catalysts based on naturally abundant first-row transition metals including cobalt [8]. As such, a growing number of cobalt-catalyzed C-H functionalization reactions, including those for heterocycle synthesis, have been reported over the last several years to date (early 2015) [9]. The purpose of this chapter is to provide an overview of such recent advancements with classification according to the nature of the catalytically active cobalt species involved in the C-H activation event. Besides inner-sphere C-H activation reactions catalyzed by low-valent and high-valent cobalt complexes, nitrene and carbene C-H insertion reactions promoted by cobalt(II)-porphyrin metalloradical catalysts are also discussed. [Pg.319]

The most recent example of pyrrolidine synthesis by C-H functionalization was illustrated in 2014, when Che and coworkers demonstrated the synthesis of pseu-doheliotridane, a simple pyrrolidine alkaloid, by employing a ruthenium-catalyzed C-H insertion reaction (Scheme 16.44) [89]. Although diazocarbonyl compounds are generally required as the precursor of the metal carbenoid intermediate, they utilized an alkyl diazomethane as the carbene source. To this end, tosylhydrazone 192 was reacted with [Ru(TTP)(CO)] (TTP tetra(p-tolyl)porphyrin) (1 mol%) and KjCOj, which generated ruthenium carbene 193 in situ, followed by C-H insertion to produce pseudohehotridane in 95% yield with high diastereoselectivity. [Pg.544]

Inter- and intramolecular (cyclometallation) reactions of this type have been ob-.served, for instance, with titanium [408,505,683-685], hafnium [411], tantalum [426,686,687], tungsten [418,542], and ruthenium complexes [688], Not only carbene complexes but also imido complexes L M=NR of, e.g., zirconium [689,690], vanadium [691], tantalum [692], or tungsten [693] undergo C-H insertion with unactivated alkanes and arenes. Some illustrative examples are sketched in Figure 3.37. No applications in organic synthesis have yet been found for these mechanistically interesting processes. [Pg.121]

Reaction of ruthenium cyclopentadienyl bisacetonitrile carbene (22) with electron-poor acetylenes yields the allylcarbene (23).28 As evidenced from DFT calculations, the reaction is likely to proceed by NHC insertion into the ruthenium-carbene bond in the metallacyclopentatriene (24). An unexpected reaction of NHC in the coordination sphere of a metal has been disclosed.29 In this example, NHC is not coordinating the metal but is linked to a phosphorus atom with a shift of the carbene centre as shown in (25). [Pg.157]

The first ruthenium porphyrin carbene complex was reported by Balch and coworkers [ 120] by metallation of an N,N -vinyl-bridged porphyrin [ 105,121 ] with Ru3(CO)i2 (Scheme 12). In this reaction, both of the C - N bonds (vinyl) were broken. Surprisingly, this reaction also yields two ruthenium(Il) dicarbonyl complexes in which the N,N -vinyl bridge remains intact, but the ruthenium has been inserted into a pyrrole C-N bond [122,123]. Upon heating, these two complexes are converted to the axial ruthenium carbene complex. [Pg.103]

Another most recent and successful example concerns the ring-expansion metathesis polymerization (REMP) of cycloolefins using cyclic carbene-ruthenium complex. " In this reaction, the cyclic olefin coordinates onto the ruthenium active center before insertion into the cyclic carbene ring. [Pg.7]

As organoruthenium compounds are able to form the stable ruthenocene, a cyclopentadienyl ring formation reaction tends to proceed. For example, as shown in Scheme 16.7, a metallaindene of ruthenium is heated, and ruthenocene is quantitatively obtained by a carbonyl insertion and a carbene transfer [52]. On the other hand, the gas-phase thermal decomposition of Cp Ru(r/ -cyclooctadienyl) affords ruthenocene by the formation of cyclopentadienyl ring from a cycloocta-dienyl ring as shown in eq. (16.29) [32]. [Pg.355]


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See also in sourсe #XX -- [ Pg.33 ]




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