Metal mediated reaction with

However, such halogenated Pcs can also be the starting point for carbon-carbon bond formation by other metal-mediated reactions with terminal alkenyl-containing building blocks [39], In terms of incorporation of alkenyl linkers for the fabrication... 

In general, as can be discerned from the example discussed above, silyl enol ethers are excellent nucleophiles for metal-mediated reactions with chiral acetals. An interesting example of an intramolecular reaction is to be found in the formation of the cis-tetrahydropyranone 19 from the 2,4-di-substituted cis-dioxolane 18 (Equation 2) [15]. 

Thus, a highly reactive species is needed to make this type of bond activation reaction feasible under mild conditions. In addition, to be useful, the C-H bond activation must occur with both high chemo- and regiose-lectivity. Over the past several decades, it has been shown that transition metal complexes are able to carry out alkane activation reactions (1-5). Many of these metal-mediated reactions operate under mild to moderate conditions and exhibit the desirable chemoselectivity and regioselectiv-ity. Thus, using transition metal complexes, alkane activation can be preferred over product activation, and the terminal positions of alkanes, which actually contain the stronger C-H bonds, can be selectively activated. The fact that a hydrocarbon C-H bond has been broken in a... 

In concurrence with the thermal metal-free version, diastereoselection is virtually complete in the metal mediated cycloaddition. In contrast to thermal, metal-free [6 + 4] cycloaddition reactions, however, the metal mediated reactions of trienes are known to furnish exclusively endo products. This is in agreement with both mechanisms,... 

Continuing with the approach of this chapter from previous years metal-mediated reactions, cycloadditions, radical processes and asymmetric applications will be highlighted. Syntheses using traditional approaches will not be covered, unless improvements are reported. Due to the volume of publications concerning pyridines and associated heterocycles many subject areas could not be covered. Combinatorial or solid-phase synthesis will not represented since the area is rather specialized and many of the processes utilize existing methodology. The synthesis and reactions of polyaza-fused systems of the pyridine class will also not be included in this review. 

Ionic liquids are a versatile class of solvents in transition metal-mediated reactions because of many projected advantages compared with conventional media, including their non-volatility. The catalytic PKR was also tested in this media, but only a narrow range of substrates provided reasonable chemical yields. ... 

The selective oxidation of C—H bonds in alkanes under mild conditions continues to attract interest from researchers. A new procedure based upon mild generation of perfluoroalkyl radicals from their corresponding anhydrides with either H2O2, m-CPBA, AIBN, or PbEt4 has been described. Oxidation of ethane under the reported conditions furnishes propionic acid and other fluorinated products.79 While some previously reported methods have involved metal-mediated functionalization of alkanes using trifluoroacetic acid/anhydride as solvent, these latter results indicate that the solvent itself without metal catalysis can react as an oxidant. As a consequence, results of these metal-mediated reactions should be treated with caution. The absolute rate constants for H-abstraction from BU3 SnH by perfluorinated w-alkyl radicals have been measured and the trends were found to be qualitatively similar to that of their addition reactions to alkenes.80 a,a-Difluorinated radicals were found to have enhanced reactivities and this was explained as being due to their pyramidal nature while multifluorinated radicals were more reactive still, owing to their electrophilic nature.80... 

The same authors have demonstrated that 1,3-diynes behave in predictable yet distinctive manners compared to simple enynes under electrophilic transition metal-mediated reaction conditions. This characteristic behaviour of 1,3-diynes is presumably caused by the slightly electron-withdrawing nature of the alkynyl substituent, which not only renders preferentially the formation of 5-exotype alkylidenes but also allows for the subsequent [l,3]-metallotropic shift. Several salient features of reactions with this functionality include the following (a) an acetate is more reactive than the tethered alkene as an initiator, generating [l,2]-acetate migrated alkylidene intermediate, whereas an alkene is a better terminator than an acetate/bromide to generate the cyclopropane moiety (b) allene products are not formed at all under current reaction conditions (c) 5-exo/6-endo-type alkylidene formation depends on the heteroatom substituent in the tether (d) facile metallotropic [1,3]-shift of the intermediate alkylidenes occurred whenever possible. 

Mainly the hydrogenations are mediated through a platinum-group-metal-catalysed reaction with chiral ligands bound to the metal. Koten and coworkers210 proposed the use of Ru- and Rh-containing catalysts immobilised on silica in asymmetric hydrogenation. As a chiral compound, they used BINAP (2,2 -bis(diphenylphosphino)-1,1 -binaphthyl) (Scheme 4). 

Although the process, which is called P-hydride elimination or simply p-elimination, is useful in organic synthesis, it competes with other reactions, thereby limiting its value. In general, since P-elimination is rapid, transition metal mediated reactions of species bearing P-hydrogens often fail. 

The synthesis of -lactams has been achieved using a variety of transition metal mediated reactions, many of which are specific to this type of compound. The vinyl epoxide (15) reacts with [Fc2(CO)9] to... 

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