Palladium-catalyzed C-C bond formation of arylhydrazines with olefins via carbon-nitrogen bond cleavage

The unactivated carbon-nitrogen bond of various aryl hydrazines was cleaved under very mild conditions by Pd(0) with the assistance of Pd(II). The in situ generated aryl palladium complex readily takes part in the C-C bond formation with olefins. This study offered a new mode of C-Pd bond formation, which will spur the development of palladium-catalyzed cross-coupling in the future.     

Palladium-catalysed asymmetric arylation of tert-cyclobutanols via enantioselective C-C bond cleavage

Palladium-catalysed arylation of tert-cyclobutanols with aryl bromide involving enantioselective C-C bond cleavage affords chiral ketones with moderate to good enantioselectivity.     

Palladium-catalyzed transformation of cyclobutanone O-benzoyloximes to nitriles via C-C bond cleavage

Palladium-catalyzed transformation of cyclobutanone O-benzoyloximes to a variety of nitriles is described. The reaction may proceed via two important steps, that is, (i) oxidative addition of the N-O bond of oximes to Pd(0) to give a cyclobutylideneaminopalladium(II) species and (ii) beta-carbon elimination of this species to afford a reactive alkylpalladium species. The kind of products is very dependent on the nature of substituents on the cyclobutane ring. The direction of the C-C bond cleavage is controlled by the kind of ligand employed. The sequential reaction composed of the C-C bond cleavage and the subsequent intra- and intermolecular C-C bond formations via the corresponding alkylpalladium species is also demonstrated. For example, an oxime having an alkynyl moiety at a suitable position reacts with a variety of alkenes to afford nitriles bearing dienylcyclopentane moiety in moderate to good yields.     

Once cleaved C-C bond was reformed: reversible C-C bond cleavage of dihydroindenyltitanium complexes

The once cleaved carbon-carbon bond of the Cp moiety in 2 was recombined in indene products. Aslo, we propose a novel mechanism for the cleavage of the carbon-carbon bond of the Cp moiety.     

Reaction of a double bond of zirconacyclopentadienes: formation of 1,2,3,5-tetrasubstituted benzenes via the C-C bond cleavage.

Reactions of zirconacyclopentadienes with dichlorocarbene afforded cyclopropanation products in good yields. In a similar manner, reactions of zirconacyclopentadienes with a Simmons-Smith type cyclopropanation reagent also gave vinylcyclopropanes in good yields after hydrolysis. Before hydrolysis, the formation of 1-zirconabicyclo[3.1.0]hexene was observed by 13C NMR spectroscopy. The 1-zirconabicyclo[3.1.0]hexene deriatives reacted with CO to produce 1,2,3,5-tetrasubstituted benzene derivatives in good yields via the C-C bond cleavage of the cyclopropane rings. This is in sharp contrast to the formation of usual 1,2,3,4-tetrasubstituted benzene derivatives from zirconacyclopentadienes.     

Unprecedented double C-C bond cleavage of a cyclopentadienyl ligand

Double C-C bond cleavage of a cyclopentadienyl ligand proceeded to titanacyclopentadienes when 2 equiv of nitriles were added and the resulting two-carbon unit and three-carbon unit were converted into a benzene derivative and a pyridine derivative, respectively, in one-pot.     

Palladium-catalyzed asymmetric arylation,vinylation, and allenylation of tert-cyclobutanols via enantioselective C-C bond cleavage

A novel enantioselective C-C bond cleavage has been achieved using palladium catalysts and chiral N,P-bidentate ligands in the asymmetric arylation, vinylation, and allenylation of tert-cyclobutanols. In these reactions, the enantioselective beta-carbon elimination of Pd(II) alcoholate formed in situ is the key step. Treatment of tert-cyclobutanols with arylating reagents in toluene in the presence of Pd(OAc)(2), a chiral ferrocene-containing N,P-bidentate ligand, and Cs(2)CO(3) affords optically active gamma-arylated ketones in excellent yields with high enantioselectivity (up to 95% ee). When vinylating reagents are used in place of arylating ones, the asymmetric vinylation also proceeds to afford optically active gamma-vinylated ketones in high yields with good to high enantioselectivity. When propargylic acetates are used, which are known to generate (sigma-allenyl)palladium complexes with Pd(0) species, asymmetric allenylation occurs to afford optically active gamma-allenylated ketones in moderate to good yields with moderate to high enantioselectivity.     

Enantioselective C-C bond cleavage creating chiral quaternary carbon centers

[Structure: see text] A chiral all-carbon benzylic quaternary carbon center is created by the asymmetric intramolecular addition/ring-opening reaction of a boryl-substituted cyclobutanone, which involves enantioselective beta-carbon elimination from a symmetrical rhodium cyclobutanolate. The asymmetric reaction was successfully applied to a synthesis of sesquiterpene, (-)-alpha-herbertenol.     

Recent advances for the photoinduced C-C bond cleavage of cycloketone oximes

Nitriles are widely existed in many bioactive compounds, and they can be easily transformed into other functional groups. Therefore, the synthesis of nitriles under cyanide-free conditions is of significant importance. Recent advances for the synthesis of nitriles through photoinduced C-C bond cleavage of cycloketone oximes classified by the type of C-X bond forming are summarized. Various compounds possessing nitriles can be efficiently accessed via this method.     

Electrochemical cleavage of a benzylic C-C bond in arylaliphatic compounds

Electrochemical cleavage of a benzylic C-C bond in arylaliphatic compounds and the effect of the structure of their alkyl and aryl fragments on the process are studied. Cleavage was found to be the most effective for substituted benzenes and anisoles with side chains bearing vicinal methoxy- and hydroxy-groups in the a- and -positions. Cleavage was moderate for cior -methoxy(hydroxy)- and (,-dialkoxyalkyl)arenes. Electrolysis carried out in methanol results in formation of PhCH₂OMe and PhCH(OMe)₂ from PhCH₂R and PhCH(OMe)R, benzaldehyde from (1,2-dihydroxypropyl)benzene, acetophenone from 2-phenylhexan-2-ol, 4-MeOC₆H₄CH(OMe)₂ from 4-(1,2-dimethoxypropyl)anisole, and 2-(MeO)₂CHC₆H₄CH(OMe)₂ from 1,2-dimethoxyindan.Translated fromIzvestiya Akademii Nauk, Seriya KMmicheskaya, No. 1, pp. 140–143, January, 1993.     

Rhodium-catalyzed rapid synthesis of substituted phenols from cyclobutenones and alkynes or alkenes via C-C bond cleavage

A novel rhodium-catalyzed synthesis of substituted phenols by the ring-opening reaction of cyclobutenones with alkynes as well as electron-deficient alkenes has been developed. Both reactions involve C-C bond cleavage of cyclobutenones, and an (η⁴-vinylketene)rhodium complex rather than a rhodacyclopentenone is considered to be a key intermediate.     

Mechanistic insight into the cleavage of an aromatic C-C bond by tungsten

The pathway for the cleavage of an aromatic C-C bond in quinoxaline by a tungsten(II) complex [W(PMe(3))(4)(η(2)-CH(2)PMe(2))H] is explored by performing detailed DFT calculations. The real active complex was found to be [W(PMe(3))(2)(η(2)-CH(2)PMe(2))H] rather than [W(PMe(3))(4)]. The key step in the whole reaction is the reductive elimination of two hydrides that are located originally on quinoxaline (see scheme).     

Pyridinyl directed alkenylation with olefins via Rh(III)-catalyzed C-C bond cleavage of secondary arylmethanols

Novel C-C bond cleavage of secondary alcohols through Rh(III)-catalyzed β-carbon elimination directed by a pyridinyl group is reported. A five-membered rhodacycle is proposed as a key intermediate, which undergoes further alkenylation with various olefins. This novel transformation shows high efficiency along with excellent selectivity in mild conditions. A wide range of functionalities are compatible. This study offers a new strategy to carry out C-C bond activation.     

New reactivity of oxaziridine: Pd(II)-catalyzed aromatic C-H ethoxycarbonylation via C-C bond cleavage

A novel Pd(II)-catalyzed aromatic C-H ethoxycarbonylation with oxaziridine involving C-C bond cleavage is described. Various aromatic 2-phenylpyridines and related compounds as well as aryl ureas can be effectively ethoxycarbonylated. A catalytic cycle involving Pd(II) and Pd(IV) is proposed.     

基于铁催化的C-H键活化构建C-C键的研究进展

过渡金属催化的C-H键活化及在此基础上的C-C键形成的反应因其高原子经济性和高效的合成效率而备受人们的关注.铁元素具有含量丰富、廉价、易得、环境友好等优点,在催化反应中得到了越来越广泛的应用.近几年来,人们关于Fe催化的C-H键活化构建C-C键反应的研究也取得了一定的进展.本文对铁催化的C-H键活化构建C-C键的最新研究进展作了综述,并且按照铁催化剂的不同价态进行了分类归纳,也对催化机理进行了阐述与总结.     

Alkynylation of benzonitriles via nickel catalyzed C-C bond activation

The scope of synthetically useful nickel catalyzed cross coupling reactions of benzonitriles has now been expanded to allow alkynylation. Thus, the cross coupling of benzonitriles with alkynylzinc reagents occurs readily in the presence of Ni/PMe₃ based catalysts to afford the respective aryl alkynes in high yields.     

Novel cyano-bridged mixed-valent copper complexes formed by completely in situ synthetic method via the cleavage of C-C bond in acetonitrile

A series of novel cyano-bridged mixed-valent copper complexes with different nuclearities, where the cyanide group is obtained from the cleavage of a carbon-carbon (C-C) bond in acetonitrile under mild conditions, have been prepared and structurally characterized via a completely in situ synthetic method. The method is catalyzed by 2,2'-bipyridine and 1,10-phenanthroline-based Cu(II) complexes in the presence of certain reductants, such as aryl aldehydes or pyridyl amines. This work provides a facile in situ synthetic method to prepare mixed-valent cyano-bridged multinuclear complexes having novel Cu(II)(CN)Cu(I)(CN)Cu(II) and Cu(II)(CN)Cu(I)(CN)Cu(I)(CN)Cu(II) units and avoids using toxic cyanides. In addition, our preliminary studies demonstrate that the mixed-valent trinuclear copper complexes can effectively catalyze the oxidation of benzaldehyde by peroxide.     

Aromatic allylation via diazotization: metal-free C-C bond formation

A new method for the synthesis of allyl aromatic compounds not involving any metal-containing reagent or catalyst has been developed. Arylamines substituted with a large number of different substituents were converted via diazotizative deamination with tert-butyl nitrite in allyl bromide and acetonitrile to the corresponding allyl aromatic compounds. The allylation reaction was found to be suitable for larger scale synthesis due to short reaction times, a nonextractive workup, and robustness toward moisture, air, and type of solvent.