C-CN bonds activation

Intramolecular Pd(0)-catalysed cyanoacylation of C=C bond in (40), involving the C—CN bond activation, has been developed as a new route to butenolides (41). DMF as a solvent, high temperatures, and short reaction times (attained by microwave irradiation) proved to minimize the competing decarbonylation. The reaction presumably proceeds with a migratory insertion of the alkyne, which is believed to be the product-determining step. ° ... 

Watson, M. R, Jacobsen, E. N. (2008). Assunmetric intramolecular arylcyanation of unactivated olefins via C-CN bond activation. Journal of the American Chemical Society, 130, 12594—12595. 

Liu, N., Wang, Z.-X. (2012). Nickel-catalyzed cross-coupling of arene- or heteroarenecarbonitriles with aryl- or heteroarylmanganese reagents through C-CN bond activation. Advanced Synthesis and Catalysis, 354, 1641-1645. 

The low-temperature reaction of allyl cyanide with the Ni hydrido dimer [NiH(dippe)]2 gives the Ni(0) complex Ni(77 -CH2=CHCH2CN)(dippe), which rearranges to the nickel(ii) allyl(cyano) complex 71 (via C-CN bond activation) and the olefin-isomerization product Ni(77 -CH3CH=GHGN)(dippe) (via C-H bond activation).The kinetics of these bond-activation processes has been studied and the role of Lewis acids in these competitive reactions has been clarified. 

C-CN bond activation through the formation of silyUsonitrile metal complexes has been disclosed for rhodium complexes by Brookhart and coworkers for the first time (Scheme 4) [39,40]. SilyUron [41], silylene-iron [41], and silylene-ruthenium [42] complexes have also been demonstrated to activate C-CN bonds. Detailed mechanistic studies have been performed on the C-CN bond activation of this type to show the intermediacy of i/ -iminoacyls, for which C-CN cleavage takes place leading to the formation of silylisonitriles. 

In spite of the rich chemistiy of stoichiometric C-CN bond activation by various transition metal complexes via the different pathways described above, their application in catalytic transformations of nitriles directed to organic synthesis has rarely emerged until the last 10 years. This review features the progress of catalytic reactions via C-CN activation (for a previous review on this topic see [43]). Particular focus of this review is on C-CN activation by metal complexes to give... 

Oxidative addition of C-CN bonds to nickel(0) can be followed by transmetalation with various main-group organometaUic reagents, and subsequent reductive elimination can result in the functionalization of C-CN bonds of nitriles (Scheme 5). As the simplest case, C-CN bonds can be transformed to C-H bonds via transmetalation with metal hydrides. Indeed, nickel-catalyzed hydrodecyanation of various aromatic and aliphatic nitriles proceeds with tetramethyldisUoxane as a hydride donor (Scheme 6) [44]. While a wide range of nitriles can be decyanated by this protocol, a relatively high amount of catalyst is required in this process, presumably because of the formation of catalyticaUy inactive (PCy3)2Ni(CN)2. The use of AlMe3 as a Lewis acid is effective in some cases to promote the C-CN bond activation. Under these reaction conditions, the relative reactivity order of different aryl electrophiles is estimated Ar-SMe>Ar-CN>Ar-OAr>Ar-OMe. 

C-CN bond activation by silylrhodium species can be applied to a catalytic cycle for silylative decyanation of nitriles, when rhodium intermediates active in C-CN activation are generated from disilanes instead of hydrosilanes (Scheme 14). The reaction proceeds with a range of nitriles, including aryl, alkenyl, and alkyl cyanides, to give the corresponding tetraorganosilanes (Scheme 15) [53, 57], although the yields of tetra-alkylsilanes are modest. 

Watson MP, Jacobsen EN (2008) Asymmetric intramolecnlar arylcyanation of unactivated olefins via C — CN bond activation. J Am Chem Soc 130(38) 12594-12595. doi 10.1021/ Ja805094J... 

This volume contains eight chapters from leading experts in the field, and is expected to provide an overview of the latest developments in C-C bond activation. It begins with mechanistic studies of transition metal-mediated C-C bond action by Prof. W.D. Jones, which laid the foundation for further discovery of catalytic reactions. The following chapters from Profs. Y. Nakao, C.-H. Jun, and C. J. Douglas focus on different strategies to activate unstrained C-C bonds, namely, C-CN bond activation, metal-organic cooperative catalysis, and activation of 8-acylquinolines. 

DFT studies have been performed in order to evaluate the energetics of C-H and C-CN bond activation of MeCN by the [Rh(Tp)(CNMe)] fragment and the results compared with that reported for the similar [Rh(Tp) (PMes)] moiety.[Rh(Tp)(CNCH2CMe3)] reacts with acetonitrile and benzonitrile, exhibiting C-H but not C—C activation. These results are... 

Evans ME, Jones WD. Controlling the selectivity for C-H and C-CN bond activation at rhodium a DFT examination of ligands effects. Organometallics. 2011 30 3371—3377. Evans ME, Li T, Jones WD. C-H vs C-C bond activation of acetonitrile and benzonitrile via oxidative addition rhodinm vs nickel and Cp vs Tp (Tp = hydrotris(3,5-dimethylpyrazol-l-yl)borate, Cp =l] -pentamethylcyclopenta-dienyl). J Am Chem Soc. 2010 132 16278-16284. 

It is well know that nickel(O) complexes play a crucial role in the commercial synthesis of adiponitrile (AdN), the major nylon-6,6 precursor. In the global process, the isomerization of the branched 2-methyl-3-butenenitrile (2M3BN) to the linear 3-pentenenitrile (3PN) is a key step. " Such isomerization is obtained through the C-CN bond activation involving a Ni° intermediate. 

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