Selective C−C Coupling of Vinyl Epoxides with Diborylmethide Lithium Salts

Vinyl epoxides and styrene oxide can react with diborylmethide lithium salts through an exclusive S_N2 borylmethylation/ring opening in a regio- and diastereoselective way, depending on the nature of the substrate. The ring-opening protocol provides homoallylboronates that can be transformed into challenging diastereomeric bishomoallylic alicyclic 1,3-diols. Unprecedented 3-borylated 1,2-oxaborolan-2-ol products were prepared by borylmethylation/ring opening of 2-methyl-2-vinyloxirane followed by intramolecular cyclization.     

C−S Cross-Coupling of Aryldiazonium Salts with Thiols Mediated by Gold

In this work, the coupling of aryldiazonium salts with thiols mediated by the readily accessible gold complex Me₂SAuCl is described. In the reported protocol, the addition of 2,2′-bipyridine as a ligand leads to higher yields than phosphines. The reaction proceeds at room temperature under soft mildconditions and has a broad scope in both the aryldiazonium salt and the thiol. Notably, the coupling works with aryldiazonium salts containing two additional substituents.     

Conductance of Selected Alkali Metal Salts in Aqueous Binary Mixtures of 2-Methoxyethanol at 25°C

Precise conductance measurements have been performed for lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, sodium perchlorate, and sodium tetraphenylborate in 2-methoxyethanol–water mixtures at four different mole fractions, i.e., 0.056, 0.136, 0.262, and 0.486 of 2-methoxyethanol (69.73 D 26.55) at 25°C in the concentration range 0.0004–0.0642 mol-dm^–3. The limiting molar conductivity °, the association constant K _A, and the association distance R for the solvent mixtures have been evaluated from the conductance concentration data using the 1978 Fuoss conductance equation. The single-ion conductances have been estimated using the reference electrolyte tetrabutylam-monium tetraphynylborate(Bu₄NBPh₄). The analysis of the data indicates that for most salts ion association is appreciable in the solvent mixtures with a mole fraction of the cosolvent of 0.262 or higher. The results have been interpreted in terms of ion-solvent interactions and structural changes in the mixed solvent media.     

Enantioselective Synthesis of Arylglycines via Pd-Catalyzed Coupling of Schöllkopf Bis-Lactim Ethers with Aryl Chlorides

Arylglycines are important pharmacophores present in several top-selling drugs. This compound class has now been made accessible from abundant aryl chlorides by a Pd-catalyzed Schöllkopf-type amino acid synthesis. In the presence of the catalyst methylnaphthyl(XPhos)-palladium bromide, the base lithium 2,2,6,6-tetramethylpyrrolidide and the additive ZnCl₂, tert-leucine-derived bis-lactim ethers were efficiently arylated at room temperature, reaching yields of 95 % and diastereoselectivities of 98 : 2. Hydrolysis gave the corresponding arylglycines in high enantiomeric excess.     

Thiol Functionalised Supports for Controlled Metal Nanoparticle Formation for Improved C–C Coupling

The myriad applications of metal nanoparticle systems have individual demands on their size, shape and electronic states, demanding novel synthetic methods to optimise these properties. Herein we report our method of exploiting strong thiol-Pd binding as a precursor for forming small, uniform Pd nanoparticles on activation. We validate our approach with a range of characterisation techniques and contrast our design strategy with an analogous wetness impregnation method, showing the drastic improvements for catalytic C−C coupling. The presence of the thiol groups offers greater control over nanoparticle formation, particularly temperature resolution on activation, potentially allowing more targeted nanoparticle formation procedures.     

Structure, Magnetism and Spin Coupling Mechanism of Cyano-Bridged LnIII–FeIII Binuclear Metal Complexes

A series of binuclear metal complexes [Ln(L)₄(H₂O)₃Fe(CN)₆]·nH₂O (Ce(1), Pr(2), Nd(3), Sm(4), Eu(5), Gd(6), Tb(7), Dy(8), Er(9), L=2-pyrrolidinone) were prepared and the X-ray crystal structures of complexes 4, 6, and 8 were determined. All the compounds consist of an Ln–CN–Fe unit, in which an octahedral coordinated Fe^III is bridged to an Ln^III ion located in square antiprism environment by a cyano group. The magnetic properties of 3, 4, 5, 6, 7, 9 show an overall antiferromagnetic behavior. The fitting to the experimental magnetic susceptibilities of complex 6 gave g=1.99, J=0.735 cm^–1, zJ=–0.080 cm^–1 on the basis of a binuclear spin system (S _Gd=7/2, S _Fe=1/2), revealing a ferromagnetic intra-molecular Gd–Fe interaction and an antiferromagnetic inter-molecular interaction. Results on the quantum chemical density functional theory (DFT) calculation for 6 showed that the calculated magnetic coupling constant is 8.1 cm^–1, supporting the occurrence of weak ferromagnetic intra-molecular interaction in 6. The spin density maps for 6 in the high spin ground state and broken symmetry state were obtained, and the spin–spin coupling mechanism is discussed.     

Divergent Coupling of Benzocyclobutenones with Indoles via C−H and C−C Activations

Highly selective divergent coupling reactions of benzocyclobutenones and indoles, in which the chemoselectivity is controlled by catalysts, are reported herein. The substrates undergo C2(indole)–C8(benzocyclobutenone) coupling to produce benzylated indoles and benzo[b]carbazoles in the Ni- and Ru-catalyzed reactions. A completely different selectivity pattern C2(indole)–C2(benzocyclobutenone) coupling to form arylated indoles is observed in the Rh-catalyzed reaction. Preliminary mechanistic studies suggest C−H and C−C activations in the reaction pathway. Synthetic utility of this protocol is demonstrated by the selective synthesis of three different types of carbazoles from the representative products.     

Polyaniline-Anchored Metal Salts for Michael Reaction of α,β-Unsaturated Ketones

A catalyst consisting of polyaniline-anchored metal salts is used as a Lewis acid to promote the Michael reaction of α,β-unsaturated ketones. The reaction is performed efficiently with imidazole, acetyl acetone, and ethyl acetate as Michel donors and chalcones as the acceptors under ultrasound irradiation.     

Base-Free Pd-Catalyzed C−Cl Borylation of Fluorinated Aryl Chlorides

Catalytic C−X borylation of aryl halides containing two ortho-fluorines has been found to be challenging, as most previous methods require stoichiometric amounts of base and the polyfluorinated aryl boronates suffer from protodeboronation, which is accelerated by ortho-fluorine substituents. Herein, we report that a combination of Pd(dba)₂ (dba=dibenzylideneacetone) with SPhos (2-dicyclohexylphosphino-2’,6’-dimethoxybiphenyl) as a ligand is efficient to catalyze the C-Cl borylation of aryl chlorides containing two ortho-fluorine substituents. This method, conducted under base-free conditions, is compatible with the resulting di-ortho-fluorinated aryl boronate products which are sensitive to base.     

Ring Cleavage of N-Alkylisothiazolilm Salts by Complex Metal Hydrides. Synthesis of β-Enaminothioketones

N-Alkylisothiazolium salts undergo ring cleavage when treated with complex metal hydrides to give β-enami-nothioketones in high yields.

The isothiazole nucleus is remarkably stable to chemical attack by reducing agents.¹ In fact, little work has been published on reactions involving reductive cleavage of the isothiazole ring. Thus, other azole systems as isoxazole are readily cleaved by catalytic hydrogenolysis whereas the isothiazole nucleus, in the same conditions, remains unchanged.² However there are instances in which ring cleavage occurs. For example, cleavage of isothiazole during lithiation at the 5-position gives a small proportion of a β-mercaptoenone resulting from the cleavage of the N-S bond.^3,4 Isothiazoles are reductively desulfu-rized by Raney nickel and this method has been used by Woodward in a remarkable synthesis of colchicine.⁵     

Catalytic C−H/C−F Coupling of Azoles and Acyl Fluorides

A method for the palladium/copper-catalyzed direct acylation of azoles with acyl fluorides is described. This study reports the first examples of acyl fluorides being used as acylation reagents in transition-metal-catalyzed aromatic C−H bond functionalization reactions. Depending on the reaction temperature, decarbonylative coupling may also occur. Mechanistic studies suggest that the cleavage of the aromatic C−H bond, promoted by a copper-phosphine species, is not the rate-limiting step of this acylation.     

Synthesis and Selective Coloration of Monoaza Crown Ethers Bearing Picrylamino－type Side Arms for Alkali Metal Salts and Methylamine

N-pivot lariat ethers with picrylamino group as a chromophore (1, 2 and 3) have been prepared by reaction of N-(4-aminoaryl)monoaza crown ethers with picryl chrolide,and the selective coloration of 1, 2 and 3 for alkali metal salts and amines has been studied by UV-Vis spectra.     

Photoinduced,Direct C(sp2)−H Bond Azo Coupling of Imidazoheteroarenes and Imidazoanilines with Aryl Diazonium Salts Catalyzed by Eosin Y

Herein, a greener approach to the eosin Y-Na₂ catalyzed, C(sp²)−H bond azo coupling of imidazoheteroarene with aryl diazonium salts is described, under acid free conditions. This direct photoredox process resulted in the corresponding azo products in good to excellent yields. Besides, this new approach could also be applicable to anilines, which is a poorly reactive substrate by other methods. The main features of this reaction are that it provides high yields and is gram-scalable and applicable to biologically relevant imidazoheteroarenes and -anilines.     

Synthesis,Crystal Structure of Ruthenium 1,2-Naphthoquinone-1-oxime Complex and Its Mediated C—C Coupling Reactions of Terminal Alkynes

IntroductionRecently ,wehavereportedthecoordinationchem istryof 1,2 naphthoquinone mono oxime (nqoH)towardsplatinumgroupmetalsincludingrutheniumandrhodi um .1 8ThereactionsofnqoHwithrutheniumcarbonyl[Ru3(CO) 12 ]leadtofiveisomersofmononuclearrutheni umcarbonylcomplexesof 1,2 naphthoquinone mono oxime .1 3Thepresenceoftheliablecarbonylligandsofferstheopportunitytointroduceavarietyofligandswithspe cificfunctionalgroupsintothemolecule .3Bythisstrategy ,metal containingpolymers ,supramolecular…     

Synthesis and Characterization of β—Cyclodextrin Bonded Metal Porphyrins

Reactions of 5-(p-aminophenyl)-10,15,20-triphenyl porphyrin (1) with Ru3(CO)12 or M(OCOCH3)2 (M=Ni,Mn) afforded metalloporphyrins(4-6),respectively.6-Deoxy-6-io-do-β-cyclodextrin(2) and mono(6-O-trifluoromethanesulfonyl) permethylated β-cyclodextrin(3) reacted with complexes 4-6 to give β-cyclodextrin bonded metal porphyrins (7-9) and permethylated β-cyclodextrin bonded me-tal porphyrins (10-12) respectively.These new complexes were identified by MS,IR,UV-visible and ^1H NMR spectra,and elemental analysis.     

Nitrimines: VII. Reaction of S,S′-Dimethyl-N-nitroimidodithiocarbonate with Alkali. Synthesis of S-Methyl-N-nitrothiocarbamate and Its Salts

Russian Journal of Organic Chemistry - Reaction of S,S′-dimethyl-N-nitroimidodithiocarbonate with alkali in aqueous-alcoholic solution results in salts of S-methyl-N-nitrothiocarbamate. In...     

Design and Synthesis of Bis-thioureas Ligands for Pd-Catalyzed Heck Reaction

The palladium-catalyzed arylation of olefins (the Heck reaction) is one of the most versatile tools for C-C bond formation in organic synthesis. Phosphine ligands are generally used to stabilize the reactive palladium intermediates, the air-sensitivity of phosphine ligands, however, places significant limits on their synthetic applications. Recently, Yang1 and we2 have reported Heck and Suzuki reactions of highly active arenediazonium salts and halides catalyzed by air-stable monothiourea-Pd…     

Screening of MgO——and Ce02-Based Catalysts for Carbon Dioxide Oxidative Coupling of Methane to C2＋ Hydrocarbons

The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM)have been investigated over ternary and binary metal oxide catalysts.The catalysts are prepared by doping MgO-and CeO2-based solids with oxides from alkali(Li2O),alkaline earth (CaO),and transition metal groups (WO3 or MnO).The presence of the peroxide (O2^2-)active sites on the Li2O2,revealed by Raman spectroscopy,may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts.The high reducibility of the CeO2 catalyst,an important factor in the CO2-OCM catalyst activity,may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobitity and oxygen vacancies in the CeO2 catalyst.raman and Fourier Transform Infra Red (FT-IR)spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks carresponding to the buld crystalline structures of Li2O,CaO,WO2 and MnO are detected.The performance of 5%MnO/15?O/CeO2 catalyst is the most potential among the CeO2-based catalysts,although lower than the 2%Li2O/MgO catalyst.The 2%Li2O/MgO catalyst showed the most promising C2 hydrocarbons selectivity and yield at 98.0%and 5.7%,respectively.