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N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01 mol%).

Novel N-heterocyclic carbene-palladium(II) complexes using 2-picolinic acid as the ancillary ligand have been successfully developed under mild conditions. Their catalytic activity in organic synthesis has been initially tested in the Buchwald-Hartwig amination of secondary and primary amines with aryl chlorides. Various substituents on both substrates can be tolerated, giving the desired coupling products in good to almost quantitative yields. The minimum catalyst loading can be 0.01 mol%, implying their potential application toward industrial processes.

A series of N-heterocyclic carbene-palladium(II) chlorides-1-methylindazole and -1-methylpyrazole complexes was successfully synthesized and fully characterized by X-ray single crystal diffraction. In addition, initial investigations of their catalytic activity showed that they were efficient catalysts in the C–N coupling of primary and secondary amines with aryl chlorides at low catalyst loadings.

The palladium-catalyzed chemoselective mono-amination of dichlorobenzenes was reported in this paper. Under the suitable conditions, all reactions involving the three isomers of dichlorobenzenes with various secondary and primary amines in the presence of a well-defined N-heterocyclic carbene-palladium(II)-2-methyl-4,5-dihydrooxazole complex, gave the desired mono-aminated products in moderate to high yields as the major or sole one.

A transition-metal-free, C–N bond-formation reaction between tertiary amines and aryl halides is reported. Under the optimal conditions, various aromatic and aliphatic tertiary amines react with aryl halides, including iodides, bromides, and chlorides, to give mono-aminated products, N,N-dialkylanilines and N-alkyl-N-arylanilines, in good to high yields. Based on the experimental results, the reaction is believed to occur via an aryne intermediate derived from the aryl halide.

A series of novel N-heterocyclic carbene–palladium(II)–4,5-dihydrooxazole (NHC-PdII-Ox) complexes 3 were successfully synthesized from commercially available imidazolium salts 1, PdCl2, and 4,5-dihydrooxazoles 2 in a one-step process, and these complexes showed efficient catalytic activity toward the amination of aryl chlorides. Both secondary and primary amines were tolerated under the same reaction conditions. Under the optimal reaction conditions, the expected coupling products were obtained in moderate to high yields.

A series of N-heterocyclic carbene–PdCl2–imidazole [NHC–Pd(II)–Im] complexes were synthesized and the structure of most of them was unambiguously determined by X-ray single-crystal diffraction. The structure–activity relationship of these complexes was investigated for the Suzuki–Miyaura coupling between 4-methoxyphenyl chloride and phenylboronic acid, and the effect of the NHCs and Im moieties were fully discussed. The sterically hindered IPr-based complex showed the highest catalytic activity. Copyright © 2013 John Wiley & Sons, Ltd.

A Pd(II)-catalyzed oxidative Heck-type reaction of triarylphosphines with alkenes via carbon–phosphorus bond cleavage was reported. Under the optimal reaction conditions, most reactions proceeded smoothly to give the expected coupling products in acceptable to high yields.

A series of N-heterocyclic carbene-palladium(II) chlorides-1-methylindazole and -1-methylpyrazole complexes was successfully synthesized and fully characterized by X-ray single crystal diffraction. In addition, initial investigations of their catalytic activity showed that they were efficient catalysts in the C–N coupling of primary and secondary amines with aryl chlorides at low catalyst loadings.

A new type of well-defined N-heterocyclic carbene (NHC)-palladium chloride-imidazole complexes derived from IPr HCl or IMes HCl, PdCl2 and 1-methylimidazole exhibits high catalytic activity in the room-temperature Suzuki-Miyaura coupling reactions of aryl or heteroaryl chlorides. Moreover, the large-scale (20.0 mmol) couplings in the presence of 0.01 mol% catalyst loading can also give the corresponding coupling products in high yields.

Cleavage of a CN bond of imidazolium salt derived from N-phenyl-substituted proline was observed in this laboratory. A novel imidazole-coordinated monodentate NHC–Pd(II) complex 5 was obtained as the sole product in good yield in the reaction of imidazolium salt 4 with Pd(OAc)2 in refluxing THF. The structure of complex 5 was determined unambiguously by an X-ray diffraction. The complex was found to be a good catalyst in the cross-coupling reaction of arylboronic acids with carboxylic acid anhydrides in water at room temperature. Copyright © 2011 John Wiley & Sons, Ltd.

N-Heterocyclic carbene-palladium(II)-1-methylimidazole [NHC-Pd(II)-Im] complex 1 showed efficient catalytic activity toward α-arylation of symmetric dialkyl ketones under mild conditions. It was found that the ratio of aryl chlorides and ketones drastically affected the reaction. When the ratio of aryl chlorides and ketones was 1:2, mono-arylated products can be obtained in good to high yields as the sole; while that of aryl chlorides and ketones was changed to 1:0.7, di- and mono-arylated products were obtained in good to high total yields at the same time, with the former as the major.

CuO-catalyzed Suzuki–Miyaura cross-coupling reactions of arylboronic acids with aryl iodides and bromides using 2,2′-diamino-6,6′-dimethylbiphenyl as the ligand are described in the paper. Under suitable conditions, all reactions gave the desired coupling products in moderate to excellent yields.

A novel butyl lithium ((BuLi)-Bu-n)-mediated carboxylation of vinyl idenecyclop to panes with CO2 in THF at -78 degrees C followed by the further transformation has been realized to afford the corresponding carboxylic adducts in moderate to good yields under normal conditions. The scope and limitations as well as the plausible reaction mechanism have been also discussed in this paper. (c) 2009 Elsevier Ltd. All rights reserved.

Lewis acid or Brønsted acid catalyzed reactions of vinylidene cyclopropanes (VDCPs), 1, with activated carbon-nitrogen, nitrogen-nitrogen, and iodine-nitrogen double-bond-containing compounds have been thoroughly investigated. We found that pyrrolidine and 1,2,3,4-tetrahydroquinoline derivatives can be formed in good yields in the reactions of VDCPs 1 with ethyl (arylimino)acetates 2 by a [3+2] cycloaddition or intramolecular Friedel-Crafts reaction pathway. Based on these results, we found that activated carbon-nitrogen and nitrogen-nitrogen double-bond-containing compounds, such as N-toluene-4-sulfonyl (N-Ts) imines 5 and diisopropylazodicarboxylate (7), can also react with VDCPs 1 to give [3+2] cycloaddition products in moderate to good yields in the presence of a Lewis acid. When N-tert-butoxycarbonyl aldimine 9 was used as the substrate, six-membered cycloaddition products 10 and 11 were formed in moderate yields in the presence of a Brønsted acid, trifluoromethanesulfonic acid (TfOH). The reactions of VDCPs 1 with N-Ts-iminophenyliodinane (12) were also carried out in the presence of (CuOTf)(2)C(6)H(6) and it was found that nitrogen-containing indene derivatives 13 were obtained, rather than the aziridination products. Plausible mechanisms for all of these transformations are discussed, based on the obtained results.

[reaction: see text] A number of pyrrolidine and 1,2,3,4-tetrahydroquinoline derivatives are prepared selectively in moderate to good yields by the reaction of arylvinylidenecyclopropanes 1 with ethyl (arylimino)acetates 2 in the presence of Lewis acid depending on the electronic nature both of 2 and R1 or R2 aromatic groups of 1.

A transition-metal-free, C–N bond-formation reaction between tertiary amines and aryl halides is reported. Under the optimal conditions, various aromatic and aliphatic tertiary amines react with aryl halides, including iodides, bromides, and chlorides, to give mono-aminated products, N,N-dialkylanilines and N-alkyl-N-arylanilines, in good to high yields. Based on the experimental results, the reaction is believed to occur via an aryne intermediate derived from the aryl halide.

A well-defined NHC-Pd(II)-Im complex 1 showed efficient catalytic activity toward the allyl-aryl coupling of allylic alcohols with arylboronic acids in neat water. Under the optimal reaction conditions, all reactions proceeded smoothly to give the corresponding coupling products in moderate to high yields.

The reactions of vinylidencyclopropanes 1 with diphenyl diselenide 2 in the presence of AIBN produced the corresponding products 4 or 5 in moderate to good yields under mild conditions. The transformation of 4 to the corresponding methylenecyclopropanes 6 was achieved by treatment with hydrogen peroxide (H2O2) in toluene, and these were further transformed to the corresponding naphthalene derivatives 7 by treatment with 30 mol % of TfOH in dichloromethane.

Reactions of vinylidenecyclopropanes with diaryl diselenide catalyzed by iodosobenzene diacetate produced the corresponding addition products 4 in moderate to good yields under mild conditions. The further transformation of 4 to the corresponding methylenecyctopropanes 5 has been disclosed in the presence of hydrogen peroxide (H 2 O 2 ) in toluene.

A well-defined NHC–Pd(II)–Im complex was proved to be an efficient catalyst for the Hiyama reaction of a variety of aryl chlorides with aryltrimethoxysilanes. Under the optimal conditions, all reactions took place smoothly to give the corresponding coupling products in moderate to high yields.

A total of 11 NHC-Pd(II)-imidazole complexes are synthesized and tested with respect to their catalytic activity.

A Pd(II)-catalyzed oxidative Heck-type reaction of triarylphosphines with alkenes via carbon–phosphorus bond cleavage was reported. Under the optimal reaction conditions, most reactions proceeded smoothly to give the expected coupling products in acceptable to high yields.

The application of a NHC-metal complex in pure water, which is not developed very popularly to date, is presented for the title reaction.

The new palladium chloride-imidazole complex exhibits high catalytic activity in the room-temperature Suzuki-Miyaura coupling reactions of aryl chlorides.

In the presence of a new complex, cross-coupling reaction of arylboronic acids with carboxylic acid anhydrides results in formation of diarylketones, mostly in high yields.

Highly stereo- and regioselective carbolithiation reactions of vinylidenecyclopropanes 1 were realized by treatment with lithium diisopropylamide (LDA) in THF and by quenching with various electrophiles such as aryl or aliphatic aldehydes, ketones, enones or propargyl bromide. Transformation of these adducts such as vinylcyclopropenes and allenols was also performed in the presence of Lewis acid or Bronsted acid to provide the fused and conjugated aromatic products in good to high yields under mild conditions.

[structure: see text]. Iodobenzene diacetate-mediated reactions of methylenecyclopropanes 1, vinylidenecyclopropanes 2, and a methylenecyclobutane 3a with phthalhydrazide give the corresponding [3+2] cycloaddition products in good yields under mild conditions. In these reactions, phthalhydrazide was transformed to a 1,3-dipole intermediate in the presence of iodobenzene diacetate. A plausible reaction mechanism has been proposed.

Lewis-acid-catalyzed reactions of arylvinylidenecyclopropanes having three substituents at the corresponding cyclopropyl rings have been investigated thoroughly. The reaction products are highly dependent on the substituents at the corresponding cyclopropyl rings and the electronic nature of the aryl groups. For arylvinylidenecyclopropanes bearing two alkyl groups at the C-1 position (R1, R2, R3=aryl; R4=H; R5, R6=alkyl), naphthalene derivatives were formed in the presence of Lewis-acid Eu(OTf)3 in DCE at 40 degrees C. For arylvinylidenecyclopropanes in which R1, R2, R3=aryl and R4, R5=alkyl (syn/anti isomeric mixtures), the corresponding 6aH-benzo[c]fluorine derivatives were formed in the syn-configuration via a double intramolecular Friedel-Crafts reaction when all of the aryl groups do not have electron-withdrawing groups or the corresponding indene derivatives were obtained via an intramolecular Friedel-Crafts reaction as long as one electron-deficient aryl group was attached. For arylvinylidenecyclopropanes in which R1, R2, R3, R4=aryl and R5=alkyl or H, the corresponding indene derivatives were obtained exclusively via a sterically demanding intramolecular Friedel-Crafts reaction. Lewis-acid effects and mechanistic insights have been discussed on the basis of experimental investigations.

Pd(PPh3)4-catalyzed reactions of vinylidenecyclopropanes 1 with acetic acid proceeded smoothly at 80 °C in toluene to give the corresponding acetylated dienes 2 in moderate to good yields in the presence of DPEphos ligand. The plausible mechanism is proposed on the basis of the control and deuterium labeling experiments.

An interesting rearrangement of arylvinylidenecyclopropanes having three substituents at the 1- and 2-positions of the corresponding cyclopropane catalyzed by Lewis acids to give 6aH-benzo[c]fluorine derivatives via a double intramolecular Friedel-Crafts reaction or to give an indene derivative via an intramolecular Friedel-Crafts reaction is described.