X-H (X = C, N, O, P, S) bond activations induced by beta-heterosubstituted zirconaindenes

The azazirconacyclopentene-substituted phosphines 3 and 4 have been found to activate the C-H bonds of acetylenic systems, such as methylpropiolate, diphenylphosphinoacetylene and phenylacetylene, or of methylene compounds, such as malonitrile and diethylmalonate, to give complexes 5a-c, 6a and 6b. C-H bond activation also takes place with vinylacetate. Similar reactions with amines, alcohols, enolisable ketones, phenols, phosphonates, thiols and a second-generation SH-terminated dendrimer lead through X-H bond activation (X = N, O, P, S) to new complexes 8a-c, 9, 12 a,b, 13, 14a-c, 15, 16a and 16b. The azazirconacyclopentene-substituted amine 20 reacts to form analogous complexes. Zr-X bonds of these complexes (X = C, N, O, S) can be cleaved with diphenylchlorophosphine to give P-X phosphorus derivatives in high yield.     

Photochemical reaction of benzaldehyde and benzyl alcohol with methyl acrylate

Conclusions The major low-molecular-weight product of the photochemical reaction of benzyl alcohol with methyl acrylate, in both the presence and absence of benzaldehyde, is the methyl ester of 4-methoxycarbonyl-6-oxo-6-phenylhexanoic acid (obtained in 2–16% preparative yield). The photolysis of systems containing a primary alcohol, the corresponding aldehyde, and methyl acrylate was found unsuitable for the preparation of 4-substituted-butanolides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2384–2387, October, 1985.     

Regioselectivity in nickel(0) catalyzed cycloadditions of carbon dioxide with diynes

The regioselectivity of Ni(0)-catalyzed cycloadditions of CO₂ (1 atm) with various asymmetrical diynes to afford pyrones was explored. The use of 1,3-bis-(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) provided high regioselectivity when one terminal substituent on the diyne was a methyl group and the other was medium or large in size (R_L=i-Pr, t-Bu, or TMS). In contrast, the use of a relatively small N-heterocyclic carbene, 1,3-dimesitylimidazol-2-ylidene (IMes), afforded high selectivity only when R_L was large (TMS). X-ray crystal analysis of the major isomer indicated that the relatively large R_L group was in the 3-position of the pyrone.     

Coordination properties of bidentate (N,O) and tridentate (N,O,O) heterocyclic alcohols with dimethyltin(IV)

The complex-formation equilibria of dimethyltin(IV) (DMT) with 4-hydroxymethyl imidazole (HMI) and 2,6-dihydroxymethyl pyridine (PDC) have been investigated. Stoichiometry and stability constants for the complexes formed were determined at different temperatures and 0.1?mol?L^?1 NaNO₃ ionic strength. The concentration distribution of the complexes in solution was evaluated as a function of pH. The effect of dioxane as a solvent on both protonation constants and formation constants of DMT complexes with HMI and PDC are discussed. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants were investigated.     

Regioselectivity of S-silylketene S,N acetals and titanium - (ate) - enethiolates addition to unsaturated ketones

(Z) S-Silylketene S,N acetals react with α-enones to afford exclusive 1-2 addition. Titanium enethiolates and titanium - ate - complexe enethiolates undergo 1-2, 1-4 addition.     

Palladium catalyzed α-arylation of methyl isobutyrate and isobutyronitrile: an efficient synthesis of 2,5-disubstituted benzyl alcohol and amine intermediates

Several 2,5-disubstituted benzyl alcohols containing a functionalized t-butyl moiety were synthesized via palladium catalyzed α-arylation of methyl isobutyrate and butyronitrile on synthetically useful scales. The resulting benzyl alcohols could then be further elaborated to benzyl amines or other desirable intermediates.     

Lewis acid catalyzed condensation of 2-aminohetarene N-oxides with N,N-dimethylformamide dimethyl acetal

Chemistry of Heterocyclic Compounds - A method for the introduction of the N,N-dimethylformamidine protective group in a series of six-membered 2-aminohetarene N-oxides was developed. It was shown...     

Gallium and Indium Complexes of Bis(amino thiol) (N(2)S(2)) Ligands

Three methods have been developed to prepare gallium and indium complexes of three tetradentate N(2)S(2) ligands of the general formula M(N(2)S(2))R (M = Ga, In; R = Cl, Br, SCN, O(2)CC(6)H(5)-O,O'). The ancillary ligand (Cl, SCN, O(2)CC(6)H(5)-O,O') was varied with the tetradentate ligand BAT-TM. X-ray crystallography shows that the coordination geometry about the d(10) metal ion is influenced by the steric requirements of the ligands. X-ray crystallography of four molecules results in the following data: GaCl(BAT-TM) (1), formula = C(10)H(22)ClGaN(2)S(2), space group = Pnma, a = 12.387(4) ?, b = 21.116(6) ?, c = 5.986(2) ?, V = 1565.8(9) ?(3), Z = 4; InCl(BAT-TM) (2), formula = C(10)H(22)ClInN(2)S(2), space group = Pnma, a = 12.968(9) ?, b = 29.29(1) ?, c = 5.866(2) ?, V = 1620(2) ?(3), Z = 4; InNCS(BAT-TM) (3), formula = C(11)H(24)ClInN(3)S(3), space group = Pbca, a = 11.812(3) ?, b = 11.679(3) ?, c = 24.238(9) ?, V = 3449.7 (17) ?(3), Z = 8; In(O,O'-O(2)CC(6)H(5))(BAT-TM) (4), formula = C(19)H(29)O(2)InN(2)S(2), space group = P2(1)/n, a = 10.783(2) ?, b = 18.708(4) ?, c = 12.335(4) ?, V = 2321.7(9) ?(3), Z = 4. Proton NMR studies show that the complexes are stable in solution; in polar solvents such as acetonitrile, for certain molecules, two metal-ligand complexes are observed. Similarly, two metal-ligand complexes are seen in NMR data taken in 80% acetonitrile/20% D(2)O (pD = 4.6) mixture. HPLC studies (acetonitrile/50 mM sodium acetate, pH = 4.6) show that the lipophilicity of the ligand determines the retention time of the complex.     

Kinetic study of the ruthenium(VI)‐catalyzed oxidation of benzyl alcohol by alkaline hexacyanoferrate(III)

The kinetics of the Ru(VI)‐catalyzed oxidation of benzyl alcohol by hexacyanoferrate(III), in an alkaline medium, has been studied using a spectrophotometric technique. The initial rates method was used for the kinetic analysis. The reaction is first order in [Ru(VI)], while the order changes from one to zero for both hexacyanoferrate(III) and benzyl alcohol upon increasing their concentrations. The rate data suggest a reaction mechanism based on a catalytic cycle in which ruthenate oxidizes the substrate through formation of an intermediate complex. This complex decomposes in a reversible step to produce ruthenium(IV), which is reoxidized by hexacyanoferrate(III) in a slow step. The theoretical rate law obtained is in complete agreement with all the experimental observations. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 421–429, 2002     

Interaction of chloroform with aniline, o-toluidine and N,N-dimethyl aniline

Heats of mixing aniline, o-toluidine, and N,N-dimethyl aniline with chloroform have been determined by an adiabatic calorimeter. The results have been examined for molecular interactions between them, and they indicate that aniline and o-toluidine are associated through hydrogen bonds. Enthalpy of bond formation in a 1:1 complex has also been determined.     

New insights on the Lewis acidity of diorganolead(IV) compounds: Diphenyllead(IV) complexes with N,O,S-chelating ligands

The reactions of PbPh₂(OAc)₂ with alkylglyoxylate thiosemicarbazones (HRGTSC, R = Et, Bu) afforded complexes of the type [PbPh₂(GTSC)] · H₂O, [PbPh₂(RGTSC)₂] and [PbPh₂Cl(BuGTSC)]. The structures of HRGTSC (R = Me, Et, Bu), [PbPh₂(OAc)(RGTSC)](R = Me, Et, Bu), [PbPh₂Cl(BuGTSC)] and [PbPh₂(GTSC)] · H₂O have been studied by X-ray diffraction. [PbPh₂(OAc)(RGTSC)] and [PbPh₂(GTSC)] · H₂O have [PbC₂NO₃S] kernels and the coordination sphere of the metal is pentagonal bipyramidal. [PbPh₂Cl(BuGTSC)] has a [PbC₂NOSCl] kernel and the coordination geometry around lead is pentagonal bipyramidal with one vacant site. Analysis of the bond distances in [PbPh₂(GTSC)] · H₂O suggests a significant affinity between diphenyllead(IV) and carboxylate donor groups, supporting a borderline acidic character for this organometallic cation. ¹H and ¹³C NMR spectra in DMSO-d₆ suggest the partial dissociation of the acetate in [PbPh₂(OAc)(RGTSC)] solutions and indicate some differences in the coordination mode of the two RGTSC⁻ ligands in [PbPh₂(RGTSC)₂] complexes.     

Polysiloxane xerogels with a bifunctional surface layer containing O/N, O/S, S/N, and S/S donor centers

Formation of bifunctional xerogels containing -NH₂, -SH, -P(O)(OEt)₂, and -NHP(O,S)(OEt)₂ complexing groups in the surface layer was studied using sol-gel method (fluoride ion catalyst, ethanol solvent) and three-component systems.     

Studies on photophysics and photochemistry of N-salicylidene-p-(N,N-dimethylamino)aniline

The fluorescence spectra of N-salicylidene-p-(N,N-dimethylamino)aniline have been investigated in various solvents and three kinds of fluorescence were found; they were that of excited intermediate, exciplex and excited dimer. According to the transient absorption spectra and decay kinetic data of photoproducts of the title compound, it has been found that the photoproducts in cyclohexane are a zwitterion and a mixed dimer formed by a zwitterion and an enol; in acetonitrile the photoproducts are a zwitterion, a mixed dimer formed by a zwitterion and an enol and a dimer formed of zwitterion. Photochromic and luminescence mechanisms of the title compound are discussed as well.     

Reaction of acylacetylenes and methyl propiolate with N,N′-bis(dithiocarboxy)piperazine

The reaction of N,N-bis(dithiocarboxy)piperazine with acetylenic ketones and methyl propiolate gave N,N-bis(acylvinyldithiocarbo)- and N,N -bis(methoxy-carbonylvinyldithiocarbo)piperazines. Heating the compounds obtained with perchloric acid leads to intramolecular cyclization with the formation of N,N -bis[2-acyl(methoxycarbonyl)methyl-1,3-dithietanium]piperazine perchlorates.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2637–2640, November, 1990.     

Polydentate N(2)S(2)O and N(2)S(2)O(2) Ligands as Alcoholic Derivatives of (N,N'-Bis(2-mercaptoethyl)-1,5-diazacyclooctane)nickel(II) and (N,N'-Bis(2-mercapto-2-methylpropane)-1,5-diazacyclooctane)nickel(II)

The synthesis, structural characterization, spectroscopic, and electrochemical properties of N(2)S(2)-ligated Ni(II) complexes, (N,N'-bis(2-mercaptoethyl)-1,5-diazacyclooctane)nickel(II), (bme-daco)Ni(II), and (N,N'-bis(2-mercapto-2-methylpropane)1,5-diazacyclooctane)nickel(II), (bme-daco)Ni(II), derivatized at S with alcohol-containing alkyl functionalities, are described. Reaction of (bme-daco)Ni(II) with 2-iodoethanol afforded isomers, (N,N'-bis(5-hydroxy-3-thiapentyl)-1,5-diazacyclooctane-O,N,N',S,S')halonickel(II) iodide (halo = chloro or iodo), 1, and (N,N'-bis(5-hydroxy-3-thiapentyl)-1,5-diazacyclooctane-N,N',S,S')nickel(II) iodide, 2, which differ in the utilization of binding sites in a potentially hexadentate N(2)S(2)O(2) ligand. Blue complex 1 contains nickel in an octahedral environment of N(2)S(2)OX donors; X is best modeled as Cl. It crystallizes in the monoclinic space group P2(1)/n with a = 12.580(6) ?, b = 12.291(6) ?, c = 13.090(7) ?, beta = 97.36(4) degrees, and Z = 4. In contrast, red complex 2 binds only the N(2)S(2) donor set forming a square planar nickel complex, leaving both -CH(2)CH(2)OH arms dangling; the iodide ions serve strictly as counterions. 2 crystallizes in the orthorhombic space group Pca2(1) with a = 15.822(2) ?, b = 13.171(2) ?, c = 10.0390(10) ?, and Z = 4. Reaction of (bme-daco)Ni(II) with 1,3-dibromo-2-propanol affords another octahedral Ni species with a N(2)S(2)OBr donor set, ((5-hydroxy-3,7-dithianonadiyl)-1,5-diazacyclooctane-O,N,N',S,S')bromonickel(II) bromide, 3. Complex 3 crystallizes in the orthorhombic space group Pca2(1) with a = 15.202(5) ?, b = 7.735(2) ?, c = 15.443(4) ?, and Z = 4. Complex 4.2CH(3)CN was synthesized from the reaction of (bme-daco)Ni(II) with 1,3-dibromo-2-propanol. It crystallizes in the monoclinic space group P2/c with a = 20.348(5) ?, b = 6.5120(1) ?, c = 20.548(5) ?, and Z = 4.     

Synthesis and characterization of sulfuryl diazide, O2S(N3)2

Sulfuryl diazide, O(2)S(N(3))(2), previously described as an "exceedingly explosive" compound, has been isolated and characterized by IR (Ar matrix, gas) and Raman (solid) spectroscopy, and its structure has been determined by X-ray crystallography. It has a melting point of -15 °C and can be handled in small quantities in gas, liquid, and solid states. Vibrational spectroscopic studies suggest the presence of only one conformer in both gas and solid states, and the X-ray crystallography revealed an anti conformation of the two azido groups with respect to the NSN plane. Calculations predict the anti (C(2)) conformer to be 6.6 kJ mol(-1) lower in energy than the syn (C(s)) one at the CBS-QB3 level of theory. The related chlorosulfuryl azide, ClSO(2)N(3), has also been prepared and characterized by IR and Raman spectroscopy.     

Lewis acid catalyzed direct cyanation of indoles and pyrroles with N-cyano-N-phenyl-p-toluenesulfonamide (NCTS)

BF(3)·OEt(2)-catalyzed direct cyanation of indoles and pyrroles using a less toxic, bench-stable, and easily handled electrophilic cyanating agent N-cyano-N-phenyl-para-toluenesulfonamide (NCTS) affords 3-cyanoindoles and 2-cyanopyrroles in good yields with excellent regioselectivity. The substrate scope is broad with respect to indoles and pyrroles.     

1,1'-Di(heteroatom)-functionalised ferrocenes as [N,N], [O,O] and [S,S] chelate ligands in transition metal chemistry

Dppf is one of the most useful and popular ligands in coordination chemistry. Its overwhelming success has overshadowed and arguably even delayed the development and use of closely related ferrocene-based ligands with two ligating N, O or S atoms. Recently, however, dynamic progress concerning such homo-donor ligands can be noted. This tutorial review describes the main results obtained over the past decade in order to introduce the reader to an exciting field which currently shows particularly rapid development. The material is organised in sections according to ligand type, followed by a section which summarises the applications reported so far.