Pd2dba3/P(i-BuNCH2CH2)3N: a highly efficient catalyst for the one-pot synthesis of trans-4-N,N-diarylaminostilbenes and N,N-diarylaminostyrenes

A Pd₂dba₃/P(i-BuNCH₂CH₂)₃N catalyzed one-pot synthesis of unsymmetrically substituted trans-4-N,N-diarylaminostilbenes and both symmetrically and unsymmetrically substituted N,N-diarylaminostyrene derivatives is reported. The procedure involves two or more palladium catalyzed sequential coupling reactions (an amination and an inter-molecular Heck reaction) in one-pot using the same catalyst system with two different aryl halides, including aryl chlorides and hetero aryl halides as the coupling partners.     

Copper powder-catalyzed N-arylation of imidazoles in water using 2-(hydrazinecarbonyl)pyridine N-oxides as the new ligands

2-(2-Hydrazinecarbonyl)pyridine N-oxides, which were derived from pyrrole-2-carbohydrazides and pyridine N-oxides, were synthesized and utilized as the ligands for copper powder-catalyzed N-arylation of imidazoles with aryl halides in water. Imidazoles could be arylated smoothly with various aryl halides to provide the title products in preferable yields without the need of an inert atmosphere.     

An elegant protocol for the synthesis of N-substituted pyrroles through C–N cross coupling/aromatization process using CuFe2O4 nanoparticles as catalyst under ligand-free conditions

A simple and efficient, ligand-free C–N cross-coupling of aryl halides/benzyl bromides with trans-4-hydroxy-l-proline has been developed to produce aromatized N-substituted pyrroles, using a catalytic amount of magnetically separable and recyclable CuFe₂O₄ nanoparticles, in the presence of Cs₂CO₃ in DMSO at 100 °C.     

Solvent-controlled selective synthesis of a trans-configured benzimidazoline-2-ylidene palladium(II) complex and investigations of its Heck-type catalytic activity

Reaction of N,N′-dimethylbenzimidazolyl iodide (A) with Pd(OAc)₂ in DMSO gives selectively trans-bis(N,N′-dimethylbenzimidazoline-2-ylidene) palladium(II) diiodide (trans-2) in 77% yield. The selective formation of the trans-coordination isomer and thus the cis-trans rearrangement is driven by the insolubility of trans-2 in DMSO. X-ray single-crystal diffraction analysis and ¹³C NMR spectroscopy confirm the trans-geometry of the square planar Pd(II) complex. Catalytic studies show that cis-1 and trans-2 are highly efficient in the Mizoroki-Heck coupling reaction of aryl bromides and activated aryl chlorides both in DMF and [N(n-C₄H₉)₄]Br as ionic liquid. The catalytic activities of Pd(II) complexes with N-heterocyclic carbene ligands derived from benzimidazole are comparable to their imidazole-derived analogues.     

Triphenylphosphine: a catalyst for the synthesis of C-aryl furanosides from furanosyl halides

An array of C-aryl furanosides was prepared in good yields from furanosyl halides and aryl Grignard reagents in Et₂O using PPh₃ as a catalyst.     

Synthesis of 6,7-dihydro-5H-dibenzo[c,e]azepines and biaryls by palladium-catalyzed Ullmann reaction

A novel palladium-catalyzed Ullmann protocol is described for the synthesis of 6,7-dihydro-5H-dibenzo[c,e]azepines and biaryls. In the presence of Pd(OAc)₂ and KOAc, intramolecular or intermolecular Ullmann coupling of aryl halides proceeds efficiently under ligand-free and aerobic conditions to afford the corresponding 6,7-dihydro-5H-dibenzo[c,e]azepines and biaryls in moderate to excellent yields.     

Palladium-catalyzed carbonylative synthesis of N-cyanobenzamides from aryl iodides/bromides and cyanamide

A novel and convenient protocol for the synthesis of N-cyanobenzamides starting from readily available aryl halides and cyanamide via palladium-catalyzed aminocarbonylation has been developed. The protocol utilizes Mo(CO)₆ as the CO source or CO(gas) and affords the desired N-cyanobenzamides in moderate to good yields.     

A new boronic-acid based strategy to synthesize 4(5)-(het)aryl-1H-imidazoles

This paper describes the synthesis of a new N-THP protected 5-(1H)-imidazolyl boronic acid pinacol ester and its use in Suzuki cross-coupling reactions with a wide range of (het)aryl halides to provide 4(5)-(het)aryl-1H-imidazoles.     

DAB-Cy as an inexpensive and effective ligand for palladium-catalyzed homocoupling reaction of aryl halides

A novel catalytic system of PdCl₂(CH₃CN)₂ with N,N′-dicyclohexyl-1,4-diazabutadiene (DAB-Cy) ligand was successfully used in reductive coupling of aryl halides.     

Facile stereoselective synthesis of cis- and trans-3-alkoxyazetidin-2-ones

A highly stereoselective synthesis of cis- and trans-3-alkoxy-3-phenyl/benzylthioazetidin-2-ones is described. The reaction of α-chlorosulfide-β-lactams with various alcohols catalyzed by a Lewis acid such as ZnCl₂ in the presence of molecular sieves (3-4 Å) leads to cis-3-alkoxy-3-phenyl/benzylthio-β-lactams whereas treatment of potassium 2-alkoxy-2-phenylthioethanoate with appropriate Schiff's base using POCl₃ in the presence of triethylamine leads to the formation of trans-3-alkoxy-3-phenylthioazetidin-2-ones as major products.     

Imidazol(in)ium carboxylates as N-heterocyclic carbene ligand precursors for Suzuki-Miyaura reactions

Simple catalysts formed in situ from palladium acetate and a variety of imidazolium and imidazolinium carboxylates and dithiocarboxylates have been screened in the coupling of aryl halides with trans-2-phenylvinylboronic acid. Imidazol(in)ium carboxylates show an excellent activity, which compares to that displayed by the parent imidazol(in)ium chlorides, whereas imidazol(in)ium dithiocarboxylates are poorly efficient. Interestingly, the base employed exerts a profound influence on the trans/cis stereochemistry of the coupling product.     

Immobilized triazine bis[mercapto amine] complexes of Pd(0) anchored nickel ferrite as a nanocatalyst for C–C coupling reaction

Immobilized triazine bis[mercapto amine] complexes of Pd(0) (NiFe₂O₄@TABMA-Pd(0)) was easily synthesized and applied as highly efficient and versatile nanocatalyst for the synthesis of various trans stilbenes with high performance for the Heck coupling reaction of several types of aryl halides under thermal conditions. In short reaction time, excellent yields of trans stilbene derivatives have been achieved using NiFe₂O₄@TABMA-Pd(0) catalyst.     

Silicon-carbon unsaturated compounds. 73. Photolysis of cis- and trans-1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane in the presence of tert-butyl alcohol and acetone

Irradiation of cis-1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane (1a) in the presence of tert-butyl alcohol in hexane with a low-pressure mercury lamp bearing a Vycor filter proceeded with high stereospecificity to give cis-2,3-benzo-1-tert-butoxy-1,4-dimethyl-4-phenyl-1,4-disilacyclooct-2-ene (2a), in 33% isolated yield, together with a 15% yield of 1-[(tert-butoxy)methylphenylsilyl]-4-(methylphenylsilyl)butane (3). The photolysis of trans-1,2-dimethyl-1,2-diphenyl-1,2-disilacyclohexane (1b) with tert-butyl alcohol under the same conditions gave stereospecifically trans-2,3-benzo-1-tert-butoxy-1,4-dimethyl-4-phenyl-1,4-disilacyclooct-2-ene (2b) in 41% isolated yield, along with a 12% yield of 3. Similar photolysis of 1a and 1b with tert-butyl alcohol-d₁ produced 2a and 2b, respectively, in addition to 1-[(tert-butoxy)(monodeuteriomethyl)(phenyl)silyl]-4-(methylphenylsilyl)butane. When 1a and 1b were photolyzed with acetone in a hexane solution, cis- and trans-2,3-benzo-1-isopropoxy-1,4-dimethyl-4-phenyl-1,4-disilacyclooct-2-ene (4a and 4b) were obtained in 25% and 23% isolated yield. In both photolyses, 1-(hydroxymethylphenylsilyl)-4-(methylphenylsilyl)butane (5) was also isolated in 4% and 5% yield, respectively. The photolysis of 1a with acetone-d₆ under the same conditions gave 4a-d₆ and 5-d₁ in 18% and 4% yields.     

The highly efficient Suzuki-Miyaura cross-coupling reaction using cyclopalladated N-alkylferrocenylimine as a catalyst in aqueous medium at room temperature under ambient atmosphere

A series of N-alkyl-substituted cyclopalladated ferrocenylimines were used in palladium-catalyzed Suzuki-Miyaura cross-coupling reactions of aryl halides in room temperature and CH₃OH/H₂O media under aerobic conditions. As for the catalysts, the length of N-alkyl chains has no significant effect on the catalytic activity. Using 0.01 mol% of dimer 3a in the presence of K₂CO₃ as base offered excellent yields in the reaction of activated and non-activated aryl bromides with phenylboronic acid.     

Intramolecular C-glycosylation of 2-O-benzylated pentenyl mannopyranosides: remarkable 1,2-trans stereoselectivity

The IDCP-promoted intramolecular C-glycosylation of pentenyl α-mannopyranosides carrying, at O-2, an activated benzyl group gave, unexpectedly, the 1,2-trans-fused bicyclic product which corresponds to an α-C-aryl mannopyranose derivative. This remarkable, strained C-glycosyl compound was rapidly epimerized to the more stable 1,2-cis product on treatment with BF₃·Et₂O. The IDCP-reaction product could be elaborated into a 2-(α-C-mannopyranosyl)-3,4,5-trimethoxybenzyl alcohol derivative.     

Microwave-assisted Stille and Hiyama cross-coupling reactions catalyzed by ortho-palladated complexes of homoveratrylamine

The activity of dimeric [Pd{C₆H₂(CH₂CH₂NH₂)-(OMe)₂-3,4}(μ-Br)]₂ and monomeric [Pd{C₆H₂(CH₂CH₂NH₂)-(OMe)₂-3,4}Br(PPh₃)] complexes as efficient, air, and moisture tolerant catalysts was investigated in Stille and Hiyama cross-coupling reactions of various aryl halides. Substituted biaryls were produced in excellent yields in short reaction times using these complexes. The monomeric complex had been demonstrated to be more active than the corresponding dimeric catalyst for the cross-coupling of some of aryl bromides and unreactive aryl chlorides. The combination of homogenous metal catalyst, microwave irradiation, and microwave-active polar solvents gave high yields of products in short reaction times.     

Copper(II) trans-bis-(glycinato): an efficient heterogeneous catalyst for cross coupling of phenols with aryl halides

Copper(II) trans-bis-(glycinato) complex, easily prepared by the solid state reaction of copper(II) acetate and glycine (trans-[Cu(glyo)₂·H₂O]) was found to be an efficient, recyclable, and high yielding catalyst for the Ullmann type synthesis of diaryl ethers via the cross coupling of phenols with aryl halides without using any additives at relatively low reaction temperature. The catalyst could easily be recovered by simple filtration and was reused for several runs with consistent catalytic activity.     

Synthesis and applications of a new palladacycle as a high active catalyst in the Suzuki couplings

The reaction of biphenyl-based phosphine P(o-C₆H₄Me)Ph₂ (1) with Pd(OAc)₂ in toluene affords the air and water stable palladacycle (2) as a binuclear compound which has been characterized by multi-nuclear NMR spectroscopy and elemental analysis as a mixture of cis and trans isomers with relative intensity of 1:3, respectively. This palladacycle is a highly efficient catalyst precursor for the coupling of aryl boronic acids and aryl halides. Both activated and deactivated aryl bromides and chlorides are efficiently coupled in the presence of 2 to furnish the corresponding cross-coupled products in excellent yields, and a wide variety of functional groups are tolerated in aryl halides. This methodology has also been extended for the coupling of bromoarylphosphines and bromoarylphosphine oxides with aryl boronic acids for the generation of hindered corresponding products.     

A manganese/copper bimetallic catalyst for C-N coupling reactions under mild conditions in water

An efficient and convenient bimetallic MnF₂/CuI catalyst in combination with trans-1,2-diaminocyclohexane has been developed for the cross-coupling of nitrogen heterocycles with aryl halides in water at moderate temperature. A variety of nitrogen nucleophiles including pyrazole, 7-azaindole, indazole, indole, pyrrole and imidazole afforded the corresponding products in moderate to good yields (up to 94%) under the described arylation conditions.