Carbon bond-coupling

The discoveries made possible by the use of 13C labels are outlined below. A new ene-imine carbon-carbon bond coupling reaction was discovered that afforded... 

In the planning of the carbon-carbon bond couplings, the specific reactants were selected both according to commercial availability and in order to furnish some degree of diversity in the size and flexibility of the isolated P1/P l -modified inhibitors. In addition, the styrene and benzofuran group of orf/zo-substituents may be viewed as isosteres to the active ortho-anilides. 

As soon as I was convinced that I was right, I quickly devised the degradation of 5 to 1-methylcyclohexane-1 -carboxylic acid 6.1 The formation of this degradation product proved the identity of the original carbon-carbon bond coupling process. 

An important class of carbon-carbon bond coupling reactions is the Diels-Alder reactions. An example of a Diels-Alder reaction is shown below ... 

Carbon-carbon bond coupling reactions that link alkynyl ligands are potentially important reactions for the preparation of alkyne oligomers (372) and nonlinear optical materials, as well as carbocyclic and heterocyclic compounds (373, 374). As a metal-mediated strategy to these... 

Also in the area of aminopaUadation chemistry, subsequent Heck-type reactions to enable carbon-carbon bond coupling have been reported with great success. 

Olefin metathesis [35] regioselectively ligates two olefinic sp -hybridized carbon atoms in an inter- or intramolecular sense and represents the most unusual carbon-carbon bond coupling for the synthesis of complex molecules. The latter variation is called ring-closing olefin metathesis [36] and has received considerable... 

The higher terpenes are formed not by successive addition of C5 units but by the coupling of simpler terpenes Thus the triterpenes (C30) are derived from two mole cules of farnesyl pyrophosphate and the tetraterpenes (C40) from two molecules of ger anylgeranyl pyrophosphate These carbon-carbon bond forming processes involve tail to tail couplings and proceed by a more complicated mechanism than that just described... 

In the synthesis of Win 57,273 the attachment of the group, a 2,6-dimethylpytidinyl group, involves formation of a carbon-carbon bond rather than a carbon-nitrogen bond. The method for the attachment of this group is a palladium mediated coupling reaction (77,78) of 4-tributylstarmyl-2,6-dimethylpyridine [122033-61 -8] with a 7-halo quinolone (26). 

One-bond couplings ( /ch) in saturated systems do not seem to have been investigated extensively. The value for cyclohexane (an average of couplings to axial and equatorial protons) iSk 123 Hz, and is increased by substitution adjacent to the carbon by an electronegative element, as with the aromatic systems discussed above. 

HMQC Heteronuclear multiple quantum coherence, e.g. inverse CH correlation via one-bond carbon proton-coupling, same format and information as described for ( C detected) CH COSY but much more sensitive (therefore less time-consuming) because of H detection... 

Coupling reactions and related fluoroalkylations with polytTuoioalkyl halides are induced by vanous reagents, among them metals such as copper and zinc, or by an electrochemical cell. More recently, examples of carbon-carbon bond forma tion by coupling of unsaturated fluorides have been reported Both acyclic and cyclic fluoroolefins of the type (Rp)2C=CFRp undergo reducUve dimerization on treatment with phosphines [42] (equation 33) The reaction shown in equation 33 IS also accompbshed electrocheimcally but less cleanly [43]... 

Heck reaction, palladium-catalyzed cross-coupling reactions between organohalides or triflates with olefins (72JOC2320), can take place inter- or intra-molecularly. It is a powerful carbon-carbon bond forming reaction for the preparation of alkenyl- and aryl-substituted alkenes in which only a catalytic amount of a palladium(O) complex is required. 

Together with reactions named after Heck and Suzuki, the Stille reac-tion belongs to a class of modern, palladium-catalyzed carbon-carbon bond forming reactions. The palladium-catalyzed reaction of an organotin compound 2 with a carbon electrophile 1 is called Stille coupling. 

This organometallic coupling reaction is useful in organic synthesis because it forms carbon-carbon bonds, thereby making possible the preparation of larger molecules from smaller ones. As the following examples indicate, the coupling reaction can be carried out on aryl and vinylic halides as well as on alkyl halides. 

Intermediates 18 and 19 are comparable in complexity and complementary in reactivity. Treatment of a solution of phosphonium iodide 19 in DMSO at 25 °C with several equivalents of sodium hydride produces a deep red phosphorous ylide which couples smoothly with aldehyde 18 to give cis alkene 17 accompanied by 20 % of the undesired trans olefin (see Scheme 6a). This reaction is an example of the familiar Wittig reaction,17 a most powerful carbon-carbon bond forming process in organic synthesis. 

Vinyl triflates derived from lactone enolates are also viable coupling partners In Ni(ll)/Cr(ll)-mediated carbon-carbon bond forming reactions... 

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