The nickel catalyst prepared in situ from nickel bis(acetylacetonate) [Ni(acac)2] precursor and bis(diphenylphosphino)ethane (DPPE) ligand has shown excellent performance in the hydrophosphorylation of alkynes. Markovnikov‐type regioselective addition to terminal alkynes and stereoselective addition to internal alkynes were carried out with high selectivity without an acidic co‐catalyst (in contrast to the palladium/acid catalytic system). Various H‐phosphonates and alkynes reacted smoothly in the developed catalytic system with up to 99% yield. The mechanisms of catalyst activation and C P bond formation were revealed by experimental (NMR, ESI‐MS, X‐ray) and theoretical (density functional calculations) studies. Two different pathways of the alkyne insertion in the coordination sphere of the metal are reported for the first time. 相似文献
Symmetrical internal alkynes can be prepared either by diarylation of mono‐ and bis(trimethylsilyl)acetylene (TMSA and BTMSA) catalyzed by ligand‐less palladium(II) chloride or by a di(2‐pyridyl)methylamine‐derived palladium(II ) chloride complex 1 (typical 0.1–1 mol % of Pd loading) in water using pyrrolidine as base and tetra‐n‐butylammonium bromide as additive. Alternatively, this same process is performed in NMP in the presence of tetra‐n‐butylammonium acetate (TBAA) as base with even lower Pd loadings (0.001–1 mol % Pd). The same reaction conditions are applied to the synthesis of unsymmetrical internal alkynes by monoarylation of silylated terminal alkynes. Aryl iodides can be coupled with TMSA, BTMSA and silylated terminal alkynes under heating or at room temperature, whereas for aryl bromides couplings are performed under water reflux or at 110 °C in the case of NMP. Complex 1 can be reused during several cycles either in water or in NMP without loss of catalytic activity. These simple reaction conditions allow the preparation of internal alkynes without secondary products, most probably by succesive protiodesilylation‐Sonogashira coupling. 相似文献
A series of new chiral C2‐symmetrical NCN pincer rhodium(III) complexes with bis(imidazolinyl)phenyl ligands have been conveniently synthesized from easily available materials. The complexes were subsequently applied in the enantioselective addition of terminal alkynes to trifluoropyruvates. With catalyst loading of 1.5–3.0 mol%, the alkynylation of ethyl or methyl trifluoropyruvate with a variety of electronically and structurally diverse terminal alkynes gave the optically active trifluoromethyl‐substituted tertiary propargylic alcohols with enantioselectivities of up to >99% ee and high yields. Although good to excellent enantioselectivities (85–98% ee) could be achieved only for some of the aliphatic terminal alkynes under the optimized conditions, the enantioselectivities were consistently excellent (94% to >99% ee) in the case of aromatic as well as heteroaromatic alkynes and enynes. 相似文献
An efficient and mild access to mixed dimethylalkynylaluminum reagents has been developed via a direct Lewis base‐catalyzed alumination of terminal alkynes by trimethylaluminum. The use of bis(trimethylsilyl)methylamine enables the metalation at room temperature with only 1% of catalyst loading. 相似文献
A highly effective copper catalyst has been developed that promotes the insertion of carbon dioxide into the C H bond of terminal alkynes under unprecedentedly mild conditions. For the first time, propiolic acids can thus be synthesized in excellent yields from alkynes and carbon dioxide in the presence of the mild base cesium carbonate. The catalyst, (4,7‐diphenyl‐1,10‐phenanthroline)bis[tris(4‐fluorophenyl)phosphine]copper(I) nitrate, is easy accessible and relatively stable against air and water. 相似文献
A rational catalyst development based on mechanistic and spectroscopic investigations led to the discovery of a new protocol for catalytic hydroamidation reactions that draws on easily available ruthenium trichloride trihydrate (RuCl3⋅3 H2O) as the catalyst precursor instead of the previously employed, expensive bis(2‐methylallyl)(1,5‐cyclooctadiene)ruthenium(II). This practical and easy‐to‐use protocol dramatically improves the synthetic applicability of Ru‐catalyzed hydroamidations. The catalyst, generated in situ from ruthenium(III) chloride hydrate, tri‐n‐butylphosphine, 4‐(dimethylamino)pyridine and potassium carbonate, effectively promotes the addition of secondary amides, lactams and carbamates to terminal alkynes under formation of (E)‐anti‐Markovnikov enamides. The scope of the new protocol is demonstrated by the synthesis of 24 functionalized enamide derivatives, among them valuable intermediates for organic synthesis. 相似文献
The straightforward in situ synthesized bis(2,6‐diisopropyl)acenaphthenequinonediimine palladium triflate catalyst was generally employed for both the mono‐alkoxycarbonylation of terminal alkynes, and the bis‐alkoxycarbonylation of 1,2‐disubstituted alkynes by using mild reaction conditions [carbon monoxide pressure (PCO)=4 bar, temperature=20 °C]. Utilizing low catalyst loading (down to 0.5 mol%), a variety of propiolic esters were synthesized with good to excellent isolated yields. Most importantly the system was very efficient not only with methanol but also with a range of different alcohols, starting from the less hindered benzyl alcohol to the most hindered ones, such as isopropyl alcohol and tert‐butyl alcohol. In addition, aromatic and aliphatic 1,2‐disubstituted alkynes were converted into maleic acid derivatives, together with an acid‐catalyzed isomerization reaction, showing modest to good selectivity and excellent combined yields. In particular 3‐hexyne showed a satisfactory degree of selectivity for the maleic diesters of methanol and benzyl alcohol, obtaining the corresponding products with good isolated yields.
An efficient heterogeneous lead sulfide‐gold catalyst has been successfully developed for the synthesis of propargylic amines via a three‐component coupling reaction of aldehyde, amine and alkyne in water. The process is simple and applicable to a diverse range of aromatic and aliphatic aldehydes, amines and alkynes. Furthermore, the catalyst is stable to air and water, and can be easily recovered and reused. 相似文献
In the presence of a cationic gold(I) catalyst and N‐halosuccinimide, both trimethylsilyl‐protected and terminal alkynes are converted into alkynyl halides. Further experiments showed that silyl‐protected alkynes undergo electrophilic iodination and bromination under Brønsted acid catalysis, whilst terminal alkynes require a cationic gold catalyst. The former reactions probably proceed via activation of the electrophile, whilst the latter reactions proceed via a gold(I) acetylide intermediate. Gold‐catalysed halogenation was further combined with gold‐catalysed hydration and subsequent annulation to provide convenient routes to iodomethyl ketones and five‐membered aromatic heterocycles. 相似文献
An efficient ruthenium(II)‐catalyzed oxidative annulation reaction of various arylimidazolium salts with alkynes via N‐heterocyclic carbene‐directed C H activation to obtain substituted benzo[ij]imidazo[2,1,5‐de]quinolizinium salts is reported. This catalytic reaction proceeds in an excellent regioselective manner when using unsymmetrical alkynes as reactants. The intermediate mono‐annulated products can be obtained by reducing the amount of catalyst. Two catalytically competent N‐heterocyclic carbene‐based cyclometallated ruthenium(II) complexes have been isolated and characterized, which represent the key intermediates in the catalytic cycle. Moreover, most of the products show a strong fluorescent property, indicating their potential for making new light‐emitting materials.
A novel application of nanoparticles of paramagnetic magnetite (Fe3O4) as an efficient catalyst for carbon‐carbon bond formation via the Sonogashira–Hagihara reaction under heterogeneous ligand‐free conditions in ethylene glycol (EG) is described. By using this catalyst, arylalkynes are produced from the reaction of aryl iodides and activated heteroaryl bromides with alkynes. The results are reproducible using the catalyst, which was prepared from different sources. The catalyst is easily separated by an external magnetic field from the reaction mixture. The separated catalyst can be recycled for several consecutive runs without appreciable loss of its catalytic activity. 相似文献
Short and versatile syntheses of reusable diarylphosphinopolystyrene‐supported palladium catalysts 3a – j are described. The bis(o‐tolyl)phosphino catalyst 3b is particularly efficient for the Suzuki and Sonogashira cross‐couplings, whereas the bis(m‐tolyl)phosphino catalyst 3c is the most active catalyst for Heck reactions. The couplings are performed under non‐anhydrous reaction conditions and require only low amounts of supported palladium (0.5 mequivs. for Suzuki–Miyaura, 1.0 mequiv. for Sonogashira and 0.5 mequivs. for Heck reactions could be sufficient). Catalysts 3a–j are recovered by filtration and can be reused more than four times with no loss of efficiency. 相似文献
Hydrolytically stable, crosslinking bis(acrylamide)s 1a – 1l or bis(methacrylamide)s 2a – 2c were synthesized by reaction of acryloyl or methacryloyl chloride using primary or secondary amines. In addition, monomers 3a and 3b were obtained by amidation of 2,6‐dimethylene‐4‐oxaheptane‐1,7‐dicarboxylic acid (DMOHDA) with propylamine and diethylamine, respectively. The structures of the monomers were characterized by IR, 1H, and 13C NMR spectroscopy. All monomers containing N,N′‐monosubstituted carbamide groups were solids. Those containing N,N′‐disubstituted carbamide groups were water‐soluble liquids. Water‐soluble bis(acrylamide) 1d (N,N′‐diethyl‐1,3‐bis(acrylamido)propane) shows a radical polymerization reactivity in the presence of 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (AMPAHC) similar to that of glycerol dimethacrylate, as revealed by gelation experiments in water. 1d is hydrolytically stable in 20 wt.‐% phosphoric acid and can be used to substitute dimethacrylates in self‐etching dentin adhesives. Furthermore, this monomer was also suitable as a reactive diluent in composites.
The reactions of the N,N′‐diarylimidazolium and N,N′‐diarylimidazolinium salts with chlorosulfonic acid result in the formation of the respective disulfonated N‐heterocyclic carbene (NHC) precursors in reasonable yields (46–77%). Water‐soluble palladium catalyst complexes, in situ obtained from the respective sulfonated imidazolinium salt, sodium tetrachloropalladate (Na2PdCl4) and potassium hydroxide (KOH) in water, were successfully applied in the copper‐free Sonogashira coupling reaction in isopropyl alcohol/water mixtures using 0.2 mol% catalyst loading. The preformed (disulfonatedNHC)PdCl(cinnamyl) complex was used in aqueous Suzuki–Miyaura reactions at 0.1 mol% catalyst loading. The coupling protocol reported here is very useful for Sonogashira reactions of N‐ and S‐heterocyclic aryl bromides and chlorides with aryl‐ and alkylacetylenes. 相似文献
Soybean protein powders obtained by aqueous buffer and reverse micelle extractions were examined and characterized using X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), and scanning electron microscopy (SEM). These analysis methods provided detailed information about elemental distributions, surface structure, and secondary and microstructures of the protein, respectively. XPS data revealed that the O and N atomic percentages of soybean protein surfaces obtained with bis(2‐ethylhexyl) sodium sulfosuccinate (AOT)/hexane reverse micelles were higher than those obtained with aqueous buffer, whereas the percentage of atomic C was lower. The ratios of nitrogen to carbon (N/C) on the surface of soybean protein obtained through the two extraction methods were similar. The O/C ratio for soybean protein obtained from AOT reverse micelles was large. The obtained results indicated that the reverse micelles could affect the C, O, and N components on the surface of soybean proteins. Moreover, XRD and SEM results also showed the influence of AOT reverse micelles, which lead to more β‐sheet and pore structures. 相似文献
A periodic mesoporous organosilica (PMO) with chiral cyclohexyldiamine‐based nickel(II) complexes incorporated within the silica framework was prepared through a co‐condensation of (1R,2R)‐cyclohexyldiamine‐derived silane and Ph‐bridged silane followed by complexation of nickel(II) bromide in the presence of (1R,2R)‐N,N′‐dibenzylcyclohexyldiamine. Structural analyses by X‐ray powder diffraction, nitrogen sorption and transmission electron microscopy disclosed its orderly mesostructure while characterization by solid‐state NMR and X‐ray photoelectron spectroscopy demonstrated the well‐defined single‐site chiral bis(cyclohexyldiamine)‐based nickel(II) active centers incorporated within the PMO material. In particular, as a heterogeneous chiral catalyst, this periodic mesoporous organosilica showed high catalytic activity and excellent enantioselectivity in asymmetric Michael addition of 1,3‐dicarbonyl compounds to nitroalkenes (more than 92% conversions and up to 99% ee values). More importantly, this heterogeneous catalyst could be recovered easily and reused repeatedly nine times without obviously affecting its ee value, showing good potential for industrial applications. 相似文献