C- H bond functionalization and

Consider, for instance, the ionization of methane. Starting from a localized description of the neutral molecule, one can assume that the lowest state of the positive ion is obtained by removing one electron to one of the C—H bond functions, and construct in this way four possible functions of the form... 

Shi and co-workers have developed various types of C—H bond functionalization and C—C bond formation. Recently, they reported a novel transformation to realize ortho-arylation of acetanilides with trialkoxyarylsilanes through direct C—H functionalization (Equation 11.34) [72]. Furthermore, they also demonstrated a novel method for the direct construction of biaryl C—C bonds via Pd(II)-catalyzed cross-coupling of (hetero)arenes and various arylboronic acids [73]. Various aromatic rings show good selectivity, even without directing groups, under mild conditions. 

In addition, the imine-directed Rh-catalyzed olefinic C—H bond functionalization reaction has also been employed in the asymmetric synthesis of ( )-incarvillateine by the groups of Bergman and Ellman. The chiral o,p-un-saturated imine substrate 121 was subjected to slightly modified reaction conditions for the p-C—H bond functionalization and was further transformed to the desired chiral y-lactam 124, the key building block for the synthesis of ( )-incarvillateine via subsequent reduction/condensation sequence (Scheme 5.43). 

Another approach to create diverse C—H bond functionalization is to combine one C—H bond activation with a subsequent transformation which greatly enriches the diversity of the initial C—H bond functionalization products. Bearing this concept in mind, Sharma and Hartwig recently developed a one-pot process involving the linear selective Pd-catalyzed allylic C—H bond oxidation and subsequent enantioselective branched Ir-catalyzed allylic substitution to form products with new C—O, C—N, C—C, and C—S bonds (Scheme 5.67). The utility of this process was further demonstrated by an iterative sequence of C—H bond functionalization and homologations to prepare enantioenriched (l,n)-functionalized alkenes. 

Mechanisms of Chelate-Assisted C-H Bond Functionalization and Activation... 

Figure 4.28 A cross-section of results for Rh-catalyzed Indazole synthesis by C-H bond functionalization and cyclative capture as reported by Bergman s and Ellman s groups [60].

Simple RuCl2L and Ru(02CR)XL have shown the first innovations in catalytic sp C-H bond functionalization and new C-C bond formation. In the near future, no doubt that other more efficient ruthenium catalysts for C-H bond functionalization, and tolerating new functional groups to direct C-H bond activation, will be discovered and successfully applied. 

In 2005, Tsang et al. reported the new methodology for carbazole synthesis. The key feature of this methodology is the combination of a C—H bond functionalization and an intramolecular N-arylation (intramolecular C—H bond amination) starting from N-substituted-2-arylanilines. In the presence of a catalytic amount of... 

A combination of a C—H bond functionalization and an intramolecular O-aryration has also been developed. Xiao et al. reported palladium-catalyzed dibonzo-furan synthesis from 2-arylphenols 72 (Scheme 23.27) [37]. Electron-donating and... 

Brasche and Buchwald developed an efficient Cu(OAc)2-catalyzed substituted benzimidazoles and substituted Af-methyl-2-arylbenzimidazoles synthesis from readily available amidines in good to very good yields (Scheme 8.50). This transformation proceeds via direct C-H bond functionalization and C-N bond formation. The O2 was used as the oxidant and water was generated as the only by-product. The starting material amidines were prepared easily from anilines with carbonitrile derivative in advance [89]. 

This chapter is a compiladon of selected illustrative examples and is far from completed. With the exploration of new palladium catalysts, new transformations, such as a new coupling reaction, C—H bond functionalization, and the insight of the a mechanism, more and more novel cascade process will be designed and discovered by combination of two or more different types of reactions into one transformation. 

Homogeneous Hydrocarbon C-H Bond Activation and Functionalization with Platinum... 

The C-C bond-forming coupling of solvent molecules via sp2- and r/ -C-H bond functionalizations can be achieved using an iridium complex based on the TpMe2 ligand (hydridotris(3,5-dimethylpyrazolyl)borate) (Equation (64)).65... 

The arylation of common heteroarenes could be governed by the choice of conditions. Free (NH)-heteroarenes were C-arylated via selective catalytic C-H bond functionalizations. The key to these transformations was the use of MgO, which enabled the formation of a salt of the heteroarene, hence offering N-protection in situ (Equations (84) and (85)). a... 

A mechanism has been proposed for this, and related transformations, involving a chelation assisted C-H bond functionalization. Following hydride addition to the solvent, acetone, and a transmetallation reaction, reductive elimination yields the ketimine. Hydrolysis of the latter affords the ketone (Equation (131)).114 114a... 

HOMOGENEOUS HYDROCARBON C-H BOND ACTIVATION AND FUNCTIONALIZATION WITH PLATINUM... 

In this review, the recent developments in catalytic functionalization of C-H bonds by iridium complexes will be emphasized. For more information on previous work and their details, there are excellent reviews published recently on C-H bond functionalization by transition metal complexes generally [1-9], as well as with an emphasis on iridium [11, 16]. 

Oxidative amination of carbamates, sulfamates, and sulfonamides has broad utility for the preparation of value-added heterocyclic structures. Both dimeric rhodium complexes and ruthenium porphyrins are effective catalysts for saturated C-H bond functionalization, affording products in high yields and with excellent chemo-, regio-, and diastereocontrol. Initial efforts to develop these methods into practical asymmetric processes give promise that such achievements will someday be realized. Alkene aziridina-tion using sulfamates and sulfonamides has witnessed dramatic improvement with the advent of protocols that obviate use of capricious iminoiodinanes. Complexes of rhodium, ruthenium, and copper all enjoy application in this context and will continue to evolve as both achiral and chiral catalysts for aziridine synthesis. The invention of new methods for the selective and efficient intermolecular amination of saturated C-H bonds still stands, however, as one of the great challenges. 

As noted in Section 1.20, an electron in an excited MO generally cannot be considered to be localized in a particular bond. For example, consider CH4. Let 6, denote a localized C—H, bond orbital, and i the inner-shell Cl5 orbital. We can start with a localized description of the ground state with MOs i,by,b2,b3,b4 each doubly occupied. If we now suppose that we have excited an electron from the localized MO 6, to the localized C—H, antibonding MO b, we might write as the wave function for the excited state... 

C-H functionalization, 10, 121 C-H intermolecular functionalization, 10, 122 C-H intramolecular functionalization, 10, 130 olefin functionalization, 10, 155 /)3-Carbon atoms, C-H bond functionalization activated alkyl groups intermolecularly, 10, 111 activated alkyl groups intramolecularly, 10, 114 alkanes and alkyl units, 10, 102 Carbon-based ligands, alkali metal chemistry, 2, 3 Carbon-based 77-ligands, in molybdenum carbonyls alkenes, 5, 433 alkynes, 5, 435 allenes, 5, 433... 

Godula, K. and Sames, D. (2006) C—H bond functionalization in complex organic synthesis. Science, 312, 67. 

Molecular Activation. The strong reducing power of trivalent uranium enables interaction with both inert and less inert functions such as sp3 C—H bond, N2, and H20 displaying a variety of transformations and unusual bonding features. 

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