Pd nanoparticles catalyzed stereospecific synthesis of beta-aryl cinnamic esters in ionic liquids

Reaction of the catalyst 1 or Pd(OAc)(2) with tetrabutylammonium acetate, dissolved in tetrabutylammonium bromide, leads to a fast formation of Pd nanoparticles which efficiently catalyze the stereospecific reaction of cinnamates with aryl halides to give beta-aryl-substituted cinnamic esters. The role of tetrabutylammonium acetate is crucial in determining the formation of nanoparticles and stereospecificity of the C-C coupling process.     

Reusable copper-catalyzed cross-coupling reactions of aryl halides with organotins in inexpensive ionic liquids

A combination of Cu2O nanoparticles with P(o-tol)3 shows highly catalytic activity for the Stille cross-coupling reaction. A series of copper catalysts and ligands were evaluated, and Cu2O nanoparticles combined with P(o-tol)3 provided the best results. In the presence of Cu2O nanoparticles and P(o-tol)3, a variety of aryl halides including aryl chlorides underwent the Stille reaction with organotins smoothly in moderate to excellent yields using inexpensive TBAB (n-Bu4NBr) as the medium. It is noteworthy that the Cu2O/P(o-tol)3/TBAB system can be recovered and reused at least three times without any loss of catalytic activity among the reactions of aryl iodides and activated aryl bromides.     

Copper oxide nanoparticles catalyzed synthesis of aryl sulfides via cascade reaction of aryl halides with thiourea

Recyclable copper oxide nanoparticles catalyzed simple and highly efficient protocol for the synthesis of symmetrical aryl sulfides was developed by the cross-coupling of aromatic halides with inexpensive and commercially available thiourea which was used as an effective sulfur surrogate. The present cross-coupling protocol of thiourea, via cascade reaction with various substituted aryl halides, producing desired aryl sulfides, has an added advantage of avoiding foul-smelling thiols.     

Non-Sonogashira-type palladium-catalyzed coupling reactions of terminal alkynes assisted by silver(I) oxide or tetrabutylammonium fluoride

Palladium-catalyzed reaction of aryl and alkenyl halides with terminal alkynes in the presence of silver(I) oxide as an activator furnishes various arylated or alkenylated alkynes in good to excellent yields. The similar coupling reaction is also found to proceed using tetrabutylammonium fluoride (TBAF) or tetrabutylammonium hydroxide (TBAOH) as an activator.     

Mild and general cross-coupling of (alpha-Alkoxyvinyl)silanols and -silyl hydrides

(alpha-Alkoxyvinyl)silanols and (alpha-alkoxyvinyl)silyl hydrides are efficiently converted to aryl vinyl ethers by a palladium(0)-catalyzed cross-coupling reaction with aryl halides in the presence of tetrabutylammonium fluoride or hydroxide. Yields are generally high, and the reaction is compatible with a wide range of functional groups.     

Copper-catalyzed direct preparation of diaryl sulfides from aryl iodides using potassium thiocyanate as a sulfur transfer reagent

A method for direct preparation of diaryl sulfides from aryl iodides using potassium thiocyanate as a sulfur-transfer agent is reported. A catalyst system comprising of a simple copper salt, tetrabutylammonium bromide as a phase-transfer agent and water as the solvent is used. Microwave heating at 200 °C for 60 min allows for the conversion of a range of aryl iodides to the corresponding diaryl sulfides.     

Gelatin as a bioorganic reductant, ligand and support for palladium nanoparticles. Application as a catalyst for ligand- and amine-free Sonogashira-Hagihara reaction

Palladium nanoparticles were deposited and reduced by gelatin as a safe edible, naturally occurring and cheap support. No extra reducing agents were used for the generation of Pd(0) nanoparticles from the Pd(II) salt. The nanoparticles of Pd supported on gelatin were characterized by SEM, TEM and AFM images, UV-Vis and XRD spectra and the amount of palladium entrapped in the gelatin was measured by ICP and atomic absorption analysis. The nanoparticles showed high catalytic activity for the Sonogashira-Hagihara coupling reaction of various aryl iodides, bromides and chlorides as well as heteroaryl halides and also β-bromo styrene with phenylacetylene under copper-, ligand- and amine-free conditions. The reactions were carried out at 100 °C in molten tetrabutylammonium bromide (TBAB) or polyethylene glycol (PEG400) in the presence of potassium acetate as a base in argon atmosphere. Dimerization of phenylacetylene applying similar conditions in air is also described.     

Cross-coupling reactions of (1-fluorovinyl)methydiphenylsilane(1) with aryl halides and aryl triflates

The cesium fluoride (CsF)-assisted cross-coupling reaction of (1-fluorovinyl)methyldiphenylsilane (1) with aryl halides and aryl triflates was examined. The reaction with aryl iodides smoothly proceeded to afford the corresponding (1-fluorovinyl)arenes in the presence of a catalytic amount of CuI and Pd(PPh(3))(4) in aprotic polar solvents such as DMF, DMI, DMA, and NMP in good yields. A variety of functional groups (nitro, ester, ketone, and ether) on the aromatic rings can be tolerated under these mild conditions. Aryl iodides are superior to aryl bromides as the coupling reaction partner. The cross-coupling reaction of 1 with aryl triflates instead of aryl halides was also accomplished in the presence of tetrabutylammonium iodide (n-Bu(4)NI) as the additive under similar conditions.     

Hydrogenation of azides over copper nanoparticle surface using ammonium formate in water

Aryl azides undergo clean reduction by copper nanoparticles and ammonium formate in water. The surface hydrogen on copper nanoparticles is considered to be the active reducing species. A variety of functionalized aryl azides and aryl sulfonyl azides are reduced by this procedure to the corresponding amines with excellent chemoselectivity in high yields.     

A ligand-free copper(I) oxide catalyzed strategy for the N-arylation of azoles in water

A simple and practical protocol has been developed for the cross-coupling of azoles and aryl iodides under ligand-free copper(I) oxide catalyzed conditions in water. The protocol uses tetrabutylammonium bromide (TBAB) as the phase-transfer catalyst, and water as the solvent, and shows good tolerance towards various functional groups.     

Nanosized Iron- or Copper-Catalyzed Homocoupling of Aryl,Heteroaryl, Benzyl,and Alkenyl Grignard Reagents

Under very mild reaction conditions, iron or copper nanoparticles efficiently promoted the homocoupling of different Grignard reagents in tetrahydrofuran at room temperature. The nanosized iron or copper particles were generated in situ in a simple and economical way from commercially available FeCl₂ or CuCl₂, respectively, an excess of lithium powder, and a catalytic amount (5 mol%) of 4,4′-di-tert-butylbiphenyl (DTBB) as electron carrier. The reaction of a series of aryl, heteroaryl, benzyl, and alkenyl Grignard reagents in the presence of a substoichiometric amount of the iron or copper nanoparticles led to the formation of the corresponding homocoupling products in good yield.     

Unexpected C-Se cross-coupling reaction: copper oxide catalyzed synthesis of symmetrical diaryl selenides via cascade reaction of selenourea with aryl halides/boronic acids

Selenourea is used as an effective selenium surrogate in the C-Se cross-coupling reaction catalyzed by copper oxide nanoparticles under ligand free conditions. This protocol has been utilized for the synthesis of a variety of symmetrical diaryl selenides in good to excellent yields from the readily available aryl halides/boronic acids.     

Cu（OAc）2/Pyrimidines-Catalyzed Cross-coupling Reactions of Aryl Iodides and Activated Aryl Bromides with Alkynes under Aerobic, Solvent-free and Palladium-free Conditions

Excellent results have been achieved in the Cu（OAc）2-catalyzed Sonogashira cross-couplings of aryl iodides and activated aryl bromides utilizing TBAF （tetrabutylammonium fluoride） as the base and 4,6-dimethoxypyrimidin-2-amine as the ligand. It is noteworthy that the reaction is conducted under aerobic, solvent-free and palladium-free conditions.     

Copper ferrite nanoparticle-mediated N-arylation of heterocycles: a ligand-free reaction

The synergistic effects of iron and copper in copper ferrite nanoparticles for the N-arylation of heterocycles with aryl halides were demonstrated. The magnetic nature of the catalyst facilitates its removal from the reaction medium for further use. Negligible leaching of Cu and Fe in consecutive cycles makes the catalyst economical and environmentally benign for C-N cross-coupling reactions.     

Transition-metal-free Suzuki-type coupling reactions: scope and limitations of the methodology

The scope and limitations of the transition-metal-free Suzuki-type coupling of aryl halides and arylboronic acids to form biaryls are presented. Confirmation that the reaction is indeed metal-free is presented. The effects of changing base, solvent, reaction temperature, phase-transfer catalyst, and substrate are shown and the implications of these results discussed in terms of their impact on the synthetic versatility of the methodology. The main findings are that the reaction works well for aryl bromides, water is necessary as a solvent for the reaction, the optimum temperature for the reaction is 150 degrees C, the reaction is best performed by using microwave promotion with the exception of an electron-poor aryl bromide example where conventional heating may be used, only limited boronic acids can be used as coupling partners, sodium carbonate is the best base for the reaction, tetrabutylammonium bromide proves to be the best phase-transfer catalyst for the reaction, the reaction is limited to couplings between aryl halides and aryl boronic acids with sp(2)-sp(3) couplings proving ineffective, and NaBPh(4) can be used in the place of phenylboronic acid as a phenylating agent.     

Palladium-nanoparticles catalyzed hydrodehalogenation of aryl chlorides in ionic liquids

Pd-nanoparticles, in molten tetrabutylammonium bromide as the solvent and tetrabutylammonium acetate as the base, catalyze the hydrodehalogenation of various aryl chlorides under hydrogen at atmospheric pressure. Recycling experiments show a decreasing activity of this catalyst due to a small leaching of palladium from the ionic liquid phase during the extraction of the reaction products with cyclohexane. On the contrary, leaching is avoided when vacuum distillation is used to separate the dehalogenated products form the reaction mixture, thus allowing an extensive recycling of the Pd-catalyst.     

Ligand-, copper-, and amine-free sonogashira reaction of aryl iodides and bromides with terminal alkynes

Conditions for an efficient ligand-, copper-, and amine-free palladium-catalyzed Sonogashira reaction of aryl iodides and bromides with terminal alkynes have been developed. Critical to the success of this new protocol is the use of tetrabutylammonium acetate as the base. Noteworthy features of this method are room-temperature conditions and the tolerance of a broad range of functional groups in both reaction partners.     

Ligand-free copper nanoparticle promoted N-arylation of azoles with aryl and heteroaryl iodides

A relatively mild, efficient, and inexpensive method for the nucleophilic aromatic substitution of the N–H heterocycles with various aryl and heteroaryl iodides using copper nanoparticles (Cu-NP) is reported. The coupling reaction has been successfully achieved with moderate to good yields.     

Palladium-Catalyzed Cross-Coupling of 2,3-Naphthoxadisilole with Aryl Halides

Palladium-catalyzed cross-coupling between 2,3-naphthoxadisilole and aryl halides in the presence of tetrabutylammonium fluoride afforded 2-aryl naphthalenes. This is first report that oxadisilole served as a partner in the palladium-catalyzed cross-coupling reactions. The reaction mechanism was also studied.     

In situ generation of palladium nanoparticles using agro waste and their use as catalyst for copper‐, amine‐ and ligand‐free Sonogashira reaction

The use of water extract of waste papaya bark ash for the in situ generation of palladium nanoparticles (Pd NPs) as an efficient and environmentally friendly basic medium for the Sonogashira reaction at room temperature is reported. This methodology follows green chemistry principles as the reaction is performed using agro waste (natural feedstock) for the generation of the Pd NPs as well as for providing a basic medium for the reaction in the absence of any additional organic or inorganic base, ligand and copper salt, giving excellent yield of cross‐coupled product at room temperature. The reaction conditions are compatible with electronically diverse aryl iodides and electronically diverse alkyne derivatives.