Access to C(sp3)-C(sp2) and C(sp2)-C(sp2) bond formation via sequential intermolecular carbopalladation of multiple carbon-carbon bonds

A synthetic strategy of 4-benzyl-substituted 1,3-butadiene derivatives through Pd-catalyzed three-component coupling reaction of benzyl chlorides, alkynes, and monosubstituted alkenes is described. This tandem coupling reaction forms a C(sp(3))-C(sp(2)) bond and a C(sp(2))-C(sp(2)) bond sequentially in a single-step operation.     

Aza-oxindole synthesis by oxidative coupling of C(sp2)-H and C(sp3)-H centers

A Cu(II) mediated oxidative C(sp(2))-H and C(sp(3))-H coupling protocol gives access to aza-oxindoles in good to excellent yield in the presence of NaOtBu as base and toluene as solvent.     

Mechanistic Insights into C(sp2)−C(sp)N Reductive Elimination from Gold(III) Cyanide Complexes

A new family of phosphine-ligated dicyanoarylgold(III) complexes has been prepared and their reactivity towards reductive elimination has been studied in detail. Both, a highly positive entropy of activation and a primary ^12/13C KIE suggest a late concerted transition state while Hammett analysis and DFT calculations indicate that the process is asynchronous. As a result, a distinct mechanism involving an asynchronous concerted reductive elimination for the overall C(sp²)−C(sp)N bond forming reaction is characterized herein, for the first time, complementing previous studies reported for C(sp³)−C(sp³), C(sp²)−C(sp²), and C(sp³)−C(sp²) bond formation processes taking place on gold(III) species.     

Formation and structure of diruthenium complexes Ru2(CO)6−n (PPh3) n {μ-C(CH=CHPh)C(Ph)C(CH=CHPh)C(Ph)} (n=1, 2)

Ruthenium carbonyl triphenylphosphine complexes Ru₂(CO)_6−n (PPh₃) _n {μ-C(CH=CHPh)C(Ph)C(CH=CHPh)C(Ph)} (n=1, 2) were obtained by the reaction of complex Ru₂(CO)₆{μ-C(CH=CHPh)C(Ph)C(CH=CHPh)C(Ph)} containing the ruthenacyclopentadiene moiety with PPh₃ in refluxing toluene. The complexes were characterized by IR and by¹H,¹³C, and³¹P NMR spectroscopy, and by X-ray analysis. The monophosphine derivative is identical to the complex formed by fragmentation of the Ru₃(CO)₈(PPh₃){μ-C(CH=CHPh)C(Ph)C(CH=CHPh)C(Ph)} cluster and contains the PPh₃ ligand at the ruthenium atom of the ruthenacyclopentadiene moiety. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1836–1843, September, 1998     

Determination of phosphatidylethanolamine molecular species in various food matrices by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS2)

A liquid chromatographic–electrospray ionization–tandem mass spectrometric (LC–ESI–MS²) method has been developed for determination of the molecular species of phosphatidylethanolamine (PE) in four food matrices (soy, egg yolk, ox liver, and krill oil). The extraction and purification method consisted of a pressurized liquid extraction procedure for total lipid (TL) extraction, purification of phospholipids (PLs) by adsorption on a silica gel column, and separation of PL classes by semi-preparative normal-phase HPLC. Separation and identification of PE molecular species were performed by reversed-phase HPLC coupled with electrospray ionization tandem mass spectrometry (ESI–MS²). Methanol containing 5 mmol L⁻¹ ammonium formate was used as the mobile phase. A variety of PE molecular species were detected in the four food matrices. (C16:0–C18:2)PE, (C18:2–C18:2)PE, and (C16:0–C18:1)PE were the major PE molecular species in soy. Egg yolk PE contained (C16:0–C18:1)PE, (C18:0–C18:1)PE, (C18:0–C18:2)PE, and (C16:0–C18:2)PE as the major molecular species. Ox liver PE was rich in the species (C18:0–C18:1)PE, (C18:0–C20:4)PE, and (C18:0–C18:2)PE. Finally, krill oil which was particularly rich in (C16:0(alkyl)–C22:6(acyl))plasmanylethanolamine (PakE), (C16:0–C22:6)PE, and (C16:0–C20:5)PE, seemed to be an interesting potential source for supplementation of food with eicosapentaenoic acid and docosahexaenoic acid.     

Original palladium pincer complexes deriving from 1,3-bis(thiophosphinoyl)indene proligands: C(sp3)-H versus C(sp2)-H bond activation

A series of original 2-indenylidene palladium pincer complexes {PdL[Ind(Ph(2)P==S)(2)]} (L = HNCy(2), PPh(3), Cl(-)) have been prepared by double C-H activation of a 1,3-bis(thiophosphinoyl)indene proligand. Crystallographic analyses and DFT calculations indicate that the bonding situation of the {Pd[Ind(Ph(2)P==S)(2)]} fragment is essentially governed by the conjugated and rigid nature of the dianionic pincer ligand, the nature of the coligand having little influence. The formation of the 2-indenylidene complexes involves either a 2-indenyl pincer or a four-membered cyclometalated complex as an intermediate, suggesting that C(sp(2))-H or C(sp(3))-H bond activation takes place. However, deuterium labelling experiences show that in all cases, C(sp(3))-H bond activation occurs followed eventually by a Pd/H exchange. Nevertheless, evidence for direct C(sp(2))-H bond activation under mild conditions is obtained when a methyl group is introduced at the indene proligand to prevent C(sp(3))-H bond activation. The ensuing dissymmetrical 2-indenyl palladium pincer complex has been fully characterized.     

Mechanistic Insights into C(sp2)−C(sp)N Reductive Elimination from Gold(III) Cyanide Complexes

A new family of phosphine‐ligated dicyanoarylgold(III) complexes has been prepared and their reactivity towards reductive elimination has been studied in detail. Both, a highly positive entropy of activation and a primary ^12/13C KIE suggest a late concerted transition state while Hammett analysis and DFT calculations indicate that the process is asynchronous. As a result, a distinct mechanism involving an asynchronous concerted reductive elimination for the overall C(sp²)?C(sp)N bond forming reaction is characterized herein, for the first time, complementing previous studies reported for C(sp³)?C(sp³), C(sp²)?C(sp²), and C(sp³)?C(sp²) bond formation processes taking place on gold(III) species.     

A PVC-based cryptand C2B22 membrane potentiometric sensor for zinc(II)

A PVC membrane electrode for zinc ions based on cryptand C2_B22 as membrane carrier was prepared. The electrode exhibits a linear stable response over a wide concentration range (5.0 × 10^–2– 5.0 × 10^–5 mol/L) with a slope of 24 mV/ decade and a limit of detection of 3.98 × 10^–5 mol/L (2.6 μg/g). It has a fast response time of about 30 s and can be used for at least 4 months without any divergence in potential. The proposed sensor revealed good selectivities for Zn²⁺ over a wide variety of other metal ions and could be used in a pH range of 4–7. It was used as an indicator electrode in potentiometric titration of zinc ion. Received: 26 February 1998 / Revised: 25 May 1998 / Accepted: 28 May 1998     

Synthesis and crystal and molecular structure of mixed-ligand compounds Eu(S2CN(C2H5)2)3(2,2′-Bipy) and Eu(S2CN(C2H5)2)3(1,10-Phen)

Synthetic procedures were developed and X-ray diffraction analysis was performed for two mixed-ligand compounds of europium(III) with diethyldithiocarbamate ions and 2,2′-bipyridyl (2,2′-Bipy) or 1,10-phenanthroline (Phen): Eu(S₂CN(C₂H₅)₂)₃(2,2′-Bipy) (I) and Eu(S₂CN(C₂H₅)₂)₃Phen (II). The structures of the complexes consist of discrete monomer molecules; the coordination polyhedron of Eu (EuN₂S₆ is a node) is a distorted dodecahedron. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 2, pp. 300–309, March–April, 1997.     

Copper-catalyzed decarboxylative C(sp2)-C(sp3) coupling reactions via radical mechanism

We have successfully developed an example of copper-catalyzed decarboxylative C(sp(2))-C(sp(3)) coupling reactions via C-H functionalization for the first time. It is noteworthy that our catalytic system is very stable, low-cost, palladium-free, ligand-free, and easily accessible.     

Thermochemistry of europium and dithiocarbamate complex Eu(C5H8NS2)3(C12H8N2)

A solid complex Eu(C₅H₈NS₂)₃(C₁₂H₈N₂) has been obtained from reaction of hydrous europium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen⋅H₂O) in absolute ethanol. IR spectrum of the complex indicated that Eu³⁺ in the complex coordinated with sulfur atoms from the APDC and nitrogen atoms from the o-phen. TG-DTG investigation provided the evidence that the title complex was decomposed into EuS. The enthalpy change of the reaction of formation of the complex in ethanol, Δ_r H _m ^θ(l), as –22.214±0.081 kJ mol^–1, and the molar heat capacity of the complex, c _m, as 61.676±0.651 J mol^–1 K^–1, at 298.15 K were determined by an RD-496 III type microcalorimeter. The enthalpy change of the reaction of formation of the complex in solid, Δ_r H _m ^θ(s), was calculated as 54.527±0.314 kJ mol^–1 through a thermochemistry cycle. Based on the thermodynamics and kinetics on the reaction of formation of the complex in ethanol at different temperatures, fundamental parameters, including the activation enthalpy (ΔH _≠ ^θ), the activation entropy (ΔS _≠ ^θ), the activation free energy (ΔG _≠ ^θ), the apparent reaction rate constant (k), the apparent activation energy (E), the pre-exponential constant (A) and the reaction order (n), were obtained. The constant-volume combustion energy of the complex, Δ_c U, was determined as –16937.88±9.79 kJ mol^–1 by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_c H _m ^θ, and standard enthalpy of formation, Δ_f H _m ^θ, were calculated to be –16953.37±9.79 and –1708.23±10.69 kJ mol^–1, respectively.     

Quantum-Chemical Study of Yb@C 60 , Yb@B 2 C 58 , and Gd@B 3 C 57 Molecules

Using the DFT PBE0/SDD method, the structural parameters of the Yb@η2-C60, Yb@η6-C60, Yb@η6-B2C58, and Gd@η6-B3C57 molecules, of corresponding anions (1,4-B2C58)2–, (1,3,5-B3C57)3–, and free radicals BkC60–k were calculated. Ytterbium is coordinated by the degraded C=C bond in the Yb@η2-C60 molecule and by the 1,4-diboratacyclohexa-1,3,5-triene fragment, in Yb@η6-B2C58. Symmetric substitution of three atoms of the cyclohexa-1,3,5-triene fragment leads to the formation of cyclopropane fragment, three 1,4-diboratacycloocta-1,3,5,7-tetraene fragments, and three boratacyclobutane fragments. The dipole moment μ(Yb@C60) is directed from the cavity center to Yb; the dipole moment μ(Gd@η6-B3C57) is greater and has the opposite direction (from B3 to Gd). The populations of the 4f-shells of the Yb and Gd atoms are conserved. The binding energy of the endoatom in Ln@BkC60–k is significantly higher than that in Yb@C60.     

Synthesis of cyclic thioethers through tandem C(sp3)-S and C(sp2)-S bond formations from alpha,beta'-dichloro vinyl ketones

The synthesis of 5- to 8-memebered cyclic thioethers 4 has been achieved through a simple two-step sequence. The present methodology utilizes the facile Friedel-Crafts acylation of terminal alkynes 1 with acid chlorides 2 followed by tandem C(sp(3))-S and C(sp(2))-S bond formations with NaSH.xH(2)O.     

Synthesis and structure of a product of interaction of acetonitrile with hydrogen bromide, [H2N=C(Me)−NH−C(Me)Br2]Br

A mixture of solid products was obtained upon absorption of dry HBr by MeCN. One of the products, [H₂N=C(Me)−NH−C(Me)Br₂]Br, was isolated as white single crystals and characterized by X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2274–2277, November, 1998.     

Investigation of the thermal properties of [Cd(hydet-en)2Pd(CN)4] AND [Zn(hydet-en)2Pd(CN)4] single crystals

Thermal properties of the single crystals have been investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. The thermodynamic parameters such as activation energy and enthalpy and thermal stability temperature of the samples were calculated from the differential thermal analysis (DTA) and TG data. The activation energies for first peak of DTA curves were found as 496.65 (for Cd–Pd) and 419.37 kJ mol^–1 (for Zn–Pd). For second peak, activation energies were calculated 116.56 (for Cd–Pd) and 173.96 kJ mol^–1 (for Zn–Pd). The thermal stability temperature values of the Cd–Pd and Zn–Pd compounds at 10°C min^–1 heating rate are determined as approximately 220.7 and 203°C, respectively. The TG results suggest that thermal stability of the Cd–Pd complex is higher than that of the Zn–Pd complex.     

Organometallic gold(I)–nickel(II)–aryldiethynyl (–C≡C(Ar)C≡C–) phosphine complexes: synthesis and multinuclear n.m.r. study

Silver triflate [AgOTf] assisted de-bromination gives [Ni(dppm/dppe/(PPh₃)₂)(OTf)₂], which on reaction with aryldiethynyls and gold(I) phosphines in CH₂Cl₂ medium, by the self assembly technique, leads to [{Ni(dppm/dppe/(PPh₃)₂}{(1,4-AB)Au(PPh₃)}₂] [{Ni₄(dppm/dppe/(PPh₃)₂)₄(1,4AB)₄}] [dppm/dppe = diphenyl phosphino-methane (1), -ethane (2), where OSO₂CF₃ is the triflate anion]. The maximum molecular peak of the corresponding molecule is observed in the ESI mass spectrum. I.r. spectra of the complexes show –C=C– and –C=N–, as well as phosphine stretching. The ¹H-n.m.r. spectra as well as ³¹P(¹H)-n.m.r. suggest solution stereochemistry, proton movement, phosphorus proton interaction. Considering all the moities there are a lot of carbon atoms in the molecule reflected by the ¹³C-n.m.r. spectrum. In the ¹H–¹H-COSY spectrum of the present complexes and contour peaks in the ¹H–¹³C-HMQC spectrum, assign the solution structure and stereo-retentive transformation in each step.     

Synthesis and Characterization of One-dimensional Dicyclohexyl-18-crown-6 Complexes with M2[Cd(mnt)2] (M = Na, K)

Two supramolecular crown ether complexes [Na(DC18C6-A)(H₂O)]{[Na(DC18C6-A)][Cd(mnt)₂]} (1) and [K(DC18C6-A)]₂[Cd(mnt)₂] (2) (DC18C6-A = cis-syn-cis-dicyclohexyl-18-crown-6, isomer A; mnt = maleonitriledithiolate) have been synthesized and characterized by elemental analysis, FT-IR spectroscopy and X-ray single crystal diffraction. Complex 1 is composed of one [Na(DC18C6-A)(H₂O)]⁺ complex cation and one {[Na(DC18C6-A)][Cd(mnt)₂]}⁻ complex anion and displays an infinite chain-like structure through N–Na–N interactions. In complex 2, [K(DC18C6-A)]⁺ complex cation and [Cd(mnt)₂]²⁻ complex anion afford a novel 1D ladder-like structure by N–K–N, N–K–S interactions.     

Synthesis of polycyclic molecules by double C(sp2)-H/C(sp3)-H arylations with a single palladium catalyst

Polycyclic molecules were obtained in good yields by double C(sp(2))-H/C(sp(3))-H arylations mediated by a single palladium/phosphine catalyst. Both double intermolecular/intramolecular and intramolecular/intramolecular C-C couplings were performed successfully, which indicates that this concept has a broad applicability for the rapid construction of molecular complexity.     

Formation of a PIII−C(sp2) bond by addition of diphenyl(trimethylsilyl)phosphine to activated acetylenes

Diphenyl(trimethylsilyl)phosphine reacts with alkoxy(alkyl)acetylenes to give mixtures of addition products, (2-alkoxy-2-trimethylsilylalkenyl)diphenylphosphines and (2-alkoxyalkenyl)diphenylphosphines. The reaction is sensitive to the solvent; in MeCN, it gives only nonsilylated products. (1-Alkoxyethenyl)diphenylphosphines were obtained as the main products upon the reaction of Ph₂PSiMe₃ with terminal alkoxyalkynes, irrespective of the reaction conditions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1792–1796, September, 1998.     

Cembrenolides of a soft coral Lobophytum sp. (coelenterata,octocorallia, alcyonacea)

The known cembrenolide sarcophin and its new acetoxy derivative — 13-acetoxy-7,8-epoxycembra-1(15),3,11-trien-2,16-olide — have been isolated from the soft coralLobophytum sp.. The compounds isolated are inhibitors of the activity of Na⁺K⁺-ATPase and are membranotropic agents. The structures of the compounds have been shown on the basis of the results of NMR spectroscopy. Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Branch, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 762–765, November–December, 1990.