Carbon-caibon

An important feature of aldol addition is that carbon-caibon bond formation occurs between the a-caibon atom of one aldehyde and the carbonyl group of another. This is because carbanion (enolate) generation can involve proton abstraction only from the a-carbon atom. The overall transfonnation can be represented schematically, as shown in Figure 18.5. 

Mixed Claisen condensations aie analogous to mixed aldol condensations and involve carbon-caibon bond fonnation between the a-caibon atom of one ester and the carbonyl car bon of another. 

Section 26.9 Carbon-caibon bond fonnation between isoprene units can be understood on the basis of nucleophilic attack of the tt electrons of a double bond on a caibocation or an allylic caibon that bears a pyrophosphate leaving group. 

Diethyl malonate has been proposed for use as a proton source in these cyclization reactions [124], It is not a sufficiently strong acid to protonate the radical-anion rapidly. However it irreversibly protonates the enol intermediate generated after carbon-caibon bond formation. In one case, control of stereochemistry in favour of the traHS-sunstituted five membered ring 39 was achieved by the addition of cerium(Ill) ions [124],... 

For cyclizations that annulate an alkene-containlng moiety onto the carbon-caibon double bond of an enone, see also page 1329, Section 6. 

The addition of hydroxy groups to the carbon-caibon double bond of an alkene (equation 1) is classed under the lUPAC nomenclature for transformations as a dihydroxy addition. Many reagents can bring about this transformation,which can proceed in a syn or anti manner, as shown in equation (2), and the type of addition which occurs depends on the reagent. 

Von Strandtmann, M., Cohen, M. P., and Shavel, J., Carbon-caibon alkylation of ena-mines with. Mannich bases. II. New synthesis of pyran-containing fused ring systems, J. Org. Chem.. 30, 3240, 1965. 

The direct anodic cleavage of saturated aliphatic carbon-caibon bonds is only possible if an electnm is removed from the highest occupied molecular orbital (HOMO) of the C— bond, e,g. due to the presence of strain in the bond. ... 

The Volume Editors have spent great time and effort in considering the format of the work. The intention is to focus on transformations in the way that synthetic chemists think about their problems. In terms of organic molecules, the work divides into the formation of carbon-caifoon bonds, the introduction of heteroatoms, and heteroatom interconversions. Thus, Volumes 1-S focus mainly on carbon-carbon bond formation, but also include many aspects of the introduction of heteroatoms. Volumes 6-8 focus on interconversion of heteroatoms, but also deal with exchange of carbon-caibon bonds for carbon-heteroatom bonds. 

The alkene metathesis reaction between carbon-caibon double bonds is now a well-established synthetic method in industrial operations and in the laboratory. Recently it has been recognized that a closely related, transition metal catalyzed reaction takes place between a carbon-carbon double bond and a carbon-oxygen double bond. lliis latter process, which can be considered as a Wittig analog, shows promise of becoming an important tool of synthesis strategy. ... 

Classical Organic Synthesis (Carbon-Caibon Bond Formation)... 

Fig. 6.24 Carbon-caibon bond lengths as a function Of the hybridization of the bonding atoms. [Data from Bent, H. A. Chem. Rev. INI. 61. 275-3II.]...

Hyurohaloccnation (see Addition mac-lions to carbon-caibon mutiipie hnnek)... 

New Mitsunobu Reagents For Carbon-Caibon Bond Foimation," Tto. S. Tsudoda, T. 

Far less important for the synthesis of important molecular frameworks are cyclization reactions involving attack of heteroatom nucleophiles on carbonyl derivatives, since these reactions are not concerned with carbon-caibon bond fonnation but rather with transforming the carbonyl derivatives into other carbonyl derivatives, such as the reductive cyclization of (58) to give the cyclic OJV-acetal (59 Scheme 28). 2... 

A tremendous advantage of catalytic alkene metathesis deals with new approaehes to make carbon-caibon bonds and espeeially eyeles and macro-cycles with catalysts tolerating funetional groups. This is a reason why this reaetion has brought a revolution in organie synthesis by redueing the number... 

Explain why carbon-nitrogen double bonds and carbon-nitrogen triple bonds can be reduced by hydride donors such as NaBH4, while carbon-carbon double bonds and carbon-caibon triple bonds cannot. 

Alternatively, a method entailing surface coating with an alcohol solution of 60% B rank phenol formaldehyde resin (PFR) and dispersant, followed by recarbonization (700°C, 60 min), was used to prepare carbon-carbon composite membranes with improved separation performance by Liang and co-workers [80], On the carbon-caibon composite membrane coated with PFR alcohol solution and added dispersant, the gas permeation rates decreased by a factor of 10, and the ideal separation factor increased, probably due to the PFR s dispersing effect. 

Carbon/caibon materials for Generation IV nuclear reactors... 

Chen YL (1965) Carbon-caibon double bond cleavage by photoaddition of Af-nitrosodialk-ylamine to olefins. J Am Chem Soc 87(20) 4642 643... 

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