bluuebunny/crossref_metadata_2025 huggingface dataset:
Derivatization of polyoxotungstates in aqueous solution. Exploration of the kinetic stability of cobalt(II)- and cobalt(III) derivatives of lacunary anions with pyridine and pyridine-type ligands
Authors: Samonte Joseph L , Pope Michael T
Published: April 2011

Four complexes of cobalt(II) with lacunary polyoxotungstate ligands, α-[PW11O39Co(H2O)]5-, α-[SiW11O39Co(H2O)]6-, α1-, and α2-[P2W17O61Co(H2O)]8- have been examined as potential precursors to substitutionally inert derivatized polytungstates that are stable in aqueous solution at near neutral pH. Replacement of the terminal water ligand by pyridine is readily achieved and the rates of exchange between bound and free pyridine were determined from NMR line widths at temperatures between 24 and 48°C. Oxidation to the aquacobalt(III) and pyridinecobalt(III) polytungstates occurs at potentials between +0.64 V (for α1-P2W17O61Co(py)]8-) and +1.00 V (for α2-[P2W17O61Co(H2O)]8-). The cobalt(III) complexes (with the exception of α-[PW11O39Co(H2O)]4- which undergoes slow reduction by the solvent) were prepared by controlled potential electrolysis and by oxidation with potassium perdisulfate. The rates of pyridine substitution on the aquacobalt(III) complexes were determined and follow the sequence α1-[P2W17O61Co(H2O)]7- (~0.5 M-1 s-1) » α2-[P2W17O61Co(H2O)]7- ~ α-[SiW11O39Co(H2O)]5-. Cesium salts of α1-[P2W17O61CoIII(L)]7- (L = pyrazine, 4,4′-bipyridine, isonicotinic acid, and the ethyl ester of isonicotinoylglycylglycine) and the "dumbbell" 2:1 complex with bridging 4,4′-bipyridine were isolated and characterized by cyclic voltammetry and 1H NMR spectroscopy.Key words: lacunary polyoxotungstates, cobalt, ligand substitution, kinetics, redox.
Fluorous biphasic catalysis. 2. Synthesis of fluoroponytailed amine ligands along with fluoroponytailed carboxylate synthons, [M(C8F17(CH2)2CO2)2] (M = Mn2+ or Co2+): Demonstration of a perfluoroheptane soluble precatalyst for alkane and alkene functionalization in the presence of tert-butyl hydroperoxide and oxygen gas
Authors: Vincent Jean-Marc , Rabion Alain , Yachandra Vittal K , Fish Richard H
Published: April 2011

Fluorous biphasic catalysis (FBC) is a relatively new concept for homogeneous catalysis where the fluorocarbon soluble catalyst resides in a separate phase from the substrate and products. Therefore, separation of the catalyst and the products occurs by a facile decantation process. In this contribution, we present the synthesis of new Rf-fluoroponytailed synthons, 2-iodo-1-perfluorooctyl-3-propanol (1), 3-perfluorooctyl-1-propanol (2), and 3-perfluorooctyl-1-iodopropane (3), a variety of new Rf-fluoroponytailed ligands (48), with starting amines, 1,4,7-triazacyclononane, bis-picolylamine, and bis-picolylaminoethylenediamine, as well as new RfMn2+ and RfCo2+ fluoroponytailed carboxylate synthons, [Mn(O2C(CH2)2C8F17)2] (9), and [Co(O2C(CH2)2C8F17)2] (10), where Rf is C8F17. The only totally perfluoralkane soluble ligand we found was 1,4,7-tris-N-(4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecyl)-1,4,7-triazacyclononane (RfTACN, 4), and it was utilized, along with synthons 9 and 10, to generate in situ RfMn2+RfTACN and RfCo2+RfTACN complexes as precatalysts for functionalization of alkanes and alkenes. We will demonstrate that indeed this novel FBC approach for the separation of the precatalyst from the substrates and (or) products is viable for oxidation of alkanes and alkenes in the presence of the necessary oxidants, tert-butyl hydroperoxide (TBHP), and O2 gas. We will also show that these oxidation reactions occur via an autoxidation mechanism under our FBC conditions, while using electron spin resonance (ESR) techniques to ascertain the redox chemistry occurring with the starting mononuclear RfMn2+RfTACN complex.Key words: fluorous solvents, biphasic catalysis, alkane/alkene oxidation.
Synthesis and spectroscopic (1H NMR, ESR) characterization of new aryloxy-Mn(II) complexes: steric control over O- vs. phenyl-π-coordination of ArO- ligands (ArO- = C6H5O-, 4-methyl-C6H4O-, 3,5-dimethyl-C6H3O-, 2,6-di-tert-butyl-C6H3O-, 2,6-dimethyl-C6H3O-) to the "Mn(II)Cp" moiety, and their reactivity with carbon dioxide
Authors: Aresta M , Tommasi I , Dileo C , Dibenedetto A , Narracci M , Ziolkowski J , Jezierski A
Published: April 2011

The coordination chemistry of phenoxide ligands, such as C6H5O, 4-(CH3)-C6H4O, 3,5-(CH3)2-C6H3O, 2,6-(tert-butyl)2-C6H3O, 2,6-(CH3)2-C6H3O, to Mn(II) has been investigated because of the possible implication of Mn(II)phenoxide complexes as intermediates in the phenylphosphate carboxylase enzyme, a protein which catalyses the selective carboxylation of phenylphosphate to 4-OH-benzoic acid using CO2. We report here the synthesis and characterization of [CpMn(µ-OAr)(THF)]2 (ArO = C6H5O, 4-(CH3)-C6H4O, 3,5-(CH3)2-C6H3O, 2,6-(CH3)2-C6H3O) and [CpMn(η5-ArO)] (ArO = 2,6-(tert-butyl)2-C6H3O and 2,6-(CH3)2-C6H3O) complexes, the first examples of mixed-sandwich complexes with Cp and phenate as π-ligands. The latter bear the 2,6-substituted phenoxide π-coordinated to the [Mn(Cp)]+ moiety. The different mode of bonding of the phenoxide ligands to Mn(II), substantiated by 1H NMR and electron spin resonance (ESR) spectroscopy, is controlled by the steric hindrance of substituents at the 2- and 6-position. The reactivity of the π-bonded ligand towards CO2 is also reported as a quite rare example of nucleophilic attack at the cumulene by the ring-carbon of the phenoxide, which is driven by electron density localization at the 4-position generated upon π-coordination to Mn(II).Key words: Mn(II)-complexes, phenoxide ligands, 1H NMR spectroscopy, ESR spectroscopy, reaction with carbon dioxide.
Scope and limitations of ruthenium-catalyzed metathesis of simple polymer-bound alkenes
Authors: Breed Peter G , Ramsden James A , Brown John M
Published: April 2011

Synthetic procedures for the preparation of two types of functional resin are described, both based on 2% cross-linked polystyrene with a high density (>60%) of side-chains and terminated by a primary alcohol. In the first case the C11 side-chain is linked to the polymer through a sulfide, and in the second an ether linkage is employed to incorporate a (CH2CH2O)4 unit. In both cases the resins have 13C NMR spectra that are informative in the chain terminus region without special operating conditions. Model intermolecular metathesis reactions were carried out on allylcarbamic acid tert-butyl ester and various alkenes with Grubbs' catalyst. On the basis of these experiments, gel-phase metathesis was successfully demonstrated between a polymer-bound allyl ether and simple symmetrical disubstituted alkenes, monitoring the extent of reaction by 13C NMR. These reactions did not go to completion even with recycling and some evidence for competing interchain metathesis is presented, based on the increased broadening and reduced mobility of the ensuing polymer.Key words: alkene metathesis, ruthenium, gel-phase, 13C NMR.
Equilibrium thermodynamic studies for the formation of 1:1 complexes of CO and ethene with a rhodium(II) porphyrin metallo-radical
Authors: Basickes Leah , Bunn Andrew G , Wayland Bradford B
Published: April 2011

Tetra(2,4,6 triisopropropyl phenyl)porphyrinatorhodium(II) ((TTiPP)RhII·1) is a persistent metal-centered radical with the odd electron in the rhodium(II) dz2orbital. (TTiPP)RhII· forms 1:1 complexes with CO and CH2CH2where the porphyrin ligand steric properties inhibit further reactions of the one-electron activated substrates.1H NMR paramagnetic shifts at a series of temperatures are used in evaluating the thermodynamics for CO complex formation with 1 to form [(TTiPP)RhII(CO)]·2 (ΔH° = -5.5 ± 0.5 kcal mol-1; ΔS° = -9 ± 1 cal K-1mol-1). Related1H NMR studies show that the bonding of 1 with ethene is less favorable than CO.Key words: rhodium porphyrin, carbon monoxide, ethene, thermodynamics, complex formation, metal-centered radical.
Selective dehydrogenation of alcohols and diols catalyzed by a dihydrido iridium PCP pincer complex
Authors: Morales-Morales David , Redón Rocío , Wang Zhaohui , Lee Do W , Yung Cathleen , Magnuson Kevin , Jensen Craig M
Published: April 2011

The PCP pincer complex, IrH2{C6H3-2,6-(CH2P-t-Bu2)2} (1) catalyzes the transfer dehydrogenation of primary and secondary alcohols. Dehydrogenation occurs across the CO bond rather than the CC bonds and the corresponding aldehydes or ketones are obtained as the sole products arising from the dehydrogenation reactions. Methanol is an exception to this pattern of reactivity and undergoes only stoichiometric dehydrogenation with 1 to give the carbonyl complex, Ir(CO){C6H3-2,6-(CH2P-t-Bu2)2} (2). The products are obtained in nearly quantitative yields when the reactions are carried out in toluene solutions. Under the same conditions, 2,5-hexanediol is converted to the annulated product, 3-methyl-2-cyclopenten-1-one which has been isolated in 91% yield in a preparative scale reaction.Key words: alcohol, dehydrogenation, ketones, iridium pincer complex, annulation.
A relationship between the catalytic carbonylation of (N-arenesulfonyl)imides and iodonium ylides
Authors: Besenyei Gábor , Neszmélyi András , Holly Sándor , Simándi László I , Párkányi László
Published: April 2011

Reactivities of various sulfonamide derivatives of general formula ArSO2N=XPhn (X = I; n = 1; X = S, Se, n = 2; X = P, As, n = 3) in catalytic carbonylations have been explained by structural properties of the substrates. Based on crystallographic data reported in the literature, it has been concluded that the two-step catalytic oxidative carbonylation of sulfonylimides proceeds only when the N=X double bond is strongly polarized. The structural requirement observed within the sulfonamide derivatives has been found to be applicable for iodonium ylides. Catalytic carbonylation of the phenyliodonium methylide (3a) prepared from dimedone (5,5-dimethyl-1,3-cyclohexanedione) and (diacetoxyiodo)benzene, resulted in a new spirobenzofuranone derivative (5a) which was characterized by X-ray single crystal diffraction, 1JC,C coupling constants, 13C-T1 relaxation times, as well as by IR and Raman spectroscopic methods. Crystals of 5a are monoclinic, space group P21/c, a = 7.187(1), b = 21.129(1), and c = 10.636(1) Å, beta = 92.81(1)°, V = 1613.2(3) Å3, and Z = 4. A ketene intermediate has been postulated in the catalytic carbonylation of the iodonium ylide. A survey of databases has revealed that the triacyl dihydrofuranone moiety in 5a constitutes a new structural unit.Key words: oxidative carbonylation, palladium catalyst, iodonium ylides, spirobenzofuranone.
Photochemical behaviour of 1,4-dichlorobenzene in aqueous solution
Authors: Meunier Laurence , Pilichowski Jean-François , Boule Pierre
Published: April 2011

Several photoproducts were identified in the direct photolysis of 1,4-dichlorobenzene (1,4-DCB) in air-saturated aqueous solution, namely 4-chlorophenol, hydroquinone, hydroxybenzoquinone, and 2,5-dichlorophenol. In the absence of oxygen the latter is not formed and phenol was detected, but the unexpected formations of 4,4'-dichlorobiphenyl, 2,4',5-trichlorobiphenyl, and a terphenyl derivative are observed. Mechanisms are proposed to explain the formations of identified photoproducts. The phototransformation of 1,4-DCB may be photoinduced by NO3 or FeIII salts. The main primary product is 2,5-dichlorophenol, which results from a hydroxylation without dechlorination. Some other products have been identified in particular 4-chlorophenol and 2,5-dichlorobenzoquinone in the case of FeIII salts.Key words: 1,4-dichlorobenzene, photolysis, aqueous solution, induced phototransformation.
A comprehensive computational examination of transannular DielsAlder reactions of unsubstituted C14 trienes  Barriers, template effects, and the CurtinHammett principle
Authors: Wolfe Saul , Buckley Anthony V , Weinberg Noham
Published: April 2011

A combination of MM3-level molecular mechanics calculations and PM3-level semiempirical molecular orbital calculations has been employed, in conjunction with an algorithm for the comprehensive conformational analysis of cyclic compounds, to obtain 1202 unique 1,3,9-cyclotetradecatriene conformations, distributed over the six possible geometrical isomers, and 70 unique transannular DielsAlder transition structures leading to the six possible stereoisomeric tricyclic olefins. A kinetic analysis that takes into account all minima of a given geometrical isomer and all transition structures leading to the same tricyclic product leads to a free energy of activation that is almost the same as the free energy difference between the lowest minimum and the lowest transition structure (the CurtinHammett principle). A substantial template effect, mainly entropic in origin, is found when the transannular reactions are compared to the DielsAlder reactions of the cognate 2,4-hexatrienes with the 2-butenes. Although the cyclization of the trans-cis-trans triene favours the cis-anti-cis over the trans-anti-trans product by more than 20 kcal mol1, the situation is reversed in the acyclic reaction. A cyclic triene that can cyclize directly to a trans-anti-trans tricycle can therefore be proposed.Key words: molecular models, Deslongchamps, Takahashi, trans-anti-trans tricycle, MM3, PM3, transition states.
Stereoselective addition of acetone to the C=N bond of [4.3.0] boron heterobicycles
Authors: Barba Victor , Cuahutle Damian , Santillan Rosa , Farfán Norberto
Published: April 2011

The reaction of N-salicylidene-2-aminophenolate (SAP-H2) derivatives with phenyl boronic acid afforded five new boron bicyclic species in moderate yields, as confirmed by an X-ray study of the boron heterocycle derived from 2-amino-4-chlorophenol. The results also showed that the boron complexes derived from Schiff bases undergo an acetolysis reaction to give the corresponding dioxazaborocines containing all substituents on the same side also in good yields. The structure of one of the addition products was established by X-ray analysis showing that, in the solid state, it exists as a dimeric structure formed by hydrogen bonds.Key words: borocines, tridentate ligands, imines, boronic acids.
An analysis of the hydration thermodynamics of the CONH group
Authors: Graziano Giuseppe
Published: April 2011

The hydration thermodynamics of the CONH group play a fundamental role for the stability of the native conformation of globular proteins, but cannot be measured in a direct manner. The values of the thermodynamic functions have to be extracted from experimental measurements on model compounds using group additivity approaches. The estimates determined by Makhatadze and Privalov in the temperature range 5100°C are used in the present study in view of their qualitative reliability. They are analyzed by means of a suitable approach that couples scaled particle theory calculations with the application of the modified Muller's model. It results that the negative entropy change is caused by the excluded volume effect for cavity creation, exaggerated in liquid water by the small size of water molecules themselves; the negative enthalpy change is determined by the H-bond energetics, formation of CONHwater H-bonds, and reorganization of waterwater H-bonds. The negative heat capacity change, a striking feature of CONH hydration thermodynamics, is because the H-bonds in the hydration shell of the CONH group are less broken than those in bulk water in the temperature range examined.Key words: peptide group, hydration, excluded volume effect, H-bonds, two-state model, negative heat capacity change.
The metal template effect on O-alkylation of tetrahydroxy[3.1.3.1]metacyclophane with 4-(chloromethyl)pyridine to afford tetrakis- [(4-pyridylmethyl)oxy][3.1.3.1]metacyclophanes and their conformational studies
Authors: Yamato Takehiko , Kumamaru Kenji , Tsuzuki Hirohisa
Published: April 2011

An attempted O-alkylation of the flexible macrocycle tetrahydroxy[3.1.3.1]metacyclophane (1) with 4-(chloromethyl) pyridine (2a) in the presence of NaH under THF reflux gave 1,3-di-O-substitution product distal-3a as a major product. In contrast, tetraol 1 was O-alkylated with 2a in the presence of Cs2CO3 to afford a mixture of two conformers of tetra-O-alkylated product 4a in a ratio of 77:23 (1,4-alternate-4a:partial-cone-4a) in 95% yield. No formation of the cone conformer in the reaction of the tetraol 1 with 2a, in comparison with those with 2-(chloromethyl) pyridine (2b) or benzyl bromide (2c) in the presence of NaH or K2CO3, which predominantly afforded cone-conformer, might be attributable to the absence of contributions derived from cationN interactions as well as cationπ interactions. The latter effect might be much smaller because of the decreased π-density of the pyridine ring compared to that of the benzene ring. The structural characterization of these products in solution as well as solid state is also discussed.Key words: macrocycles, calixarenes, cyclophanes, [3.1.3.1]metacyclophanes, O-alkylation, conformation, crystal structure, cationN interaction.
Ti5Si1.3Sb1.7  The first titanium silicide antimonide, forming a crystal structure not found in either binary system
Authors: Kleinke Holger
Published: April 2011

Ti5SixSb3x can be prepared by melting mixtures of Ti, Si, and TiSb2. The ternary phase with x = 1.32(5) crystallizes in the W5Si3 type (space group I4/mcm, Z = 8, for x = 1.32(5): a = 1034.6(2), c = 515.2(1) pm), while Ti5Sb3 and Ti5Si3 adopt the Yb5Sb3 type and the Mn5Si3 type, respectively. The Si and Sb atoms share two sites in Ti5Si1.32(5)Sb1.68: one site is located within a linear chain with short interatomic bonds, which is almost exclusively occupied by Si (i.e., 92(1)% Si and 8% Sb), whereas the second site, being occupied by 80(2)% Sb and 20% Si, shows no significant interactions between the main group elements. Band structure calculations reveal the new silicide antimonide being metallic as a consequence of partly filled Ti d states. The structure is mainly stabilized by bonding TiSb, TiSi, and SiSi interactions.Key words: titanium, silicide, antimonide, crystal structure, electronic structure, structure and bonding.
Synthesis and characterization of manganese complexes of the dibenzophospholyl ligand
Authors: Decken Andreas , Neil Melanie A , Bottomley Frank
Published: April 2011

Manganese carbonyl complexes bearing dibenzophospholyl (DBP) and 1-phenyldibenzophosphole (Ph-DBP) ligands have been prepared. Reaction of Li-DBP with Mn(CO)5Br gave (µ2-DBP)(µ2-Br)Mn2(CO)8, while reaction of bis(1,1'-dibenzophospholyl) and Mn2(CO)10 yielded (µ2-DBP)2Mn2(CO)8. The phosphine adducts (Ph-DBP)Mn2(CO)9 and (Ph-DBP)2Mn2(CO)8 were obtained by reaction of Ph-DBP and Mn2(CO)10. The ligands are σ-bonded through the phosphorus atom in all complexes. The compounds were characterized by 1H, 13C, and 31P NMR and IR spectroscopy, mass spectrometry, and X-ray diffraction.Key words: dibenzophospholyl, dibenzophosphole, manganese, heterocycle.
The total synthesis of (+)-aspicilin using 2,3-butane diacetal protected butane tetrols via a chiral memory protocol
Authors: Dixon Darren J , Foster Alison C , Ley Steven V
Published: April 2011

The total syntheses of the polyhydroxylated macrolactone (+)-aspicilin and a diastereoisomer have been achieved via a concise route, starting from the spatially desymmetrized (R',R',R,S)-2,3-butanediacetal-protected butane tetrol 13. The key steps include a regioselective silyl protection of 13 and a stereoselective Lewis acid mediated addition of allyltributylstannane to the equatorially disposed aldehyde of 4. Macrocyclization is achieved using ring closing metathesis, after which selective hydrogenation and protecting group removal yields the natural product.Key words: aspicilin, butanediacetal, desymmetrization, macrolactone, metathesis.
Synthesis of substituted phenols by directed ortho-lithiation of in situ N-silyl-protected O-aryl N-monoalkylcarbamates
Authors: Kauch Matthias , Hoppe Dieter
Published: April 2011

A simple, high-yield procedure has been developed for the ortho-lithiation and subsequent ortho-substitution of phenols by a manifold of electrophiles. N,C-Dilithiation of O-aryl N-monoalkylcarbamates proved to be impossible due to a cleavage reaction of the monolithiated intermediates. However, in situ N-silylation of O-aryl N-isopropylcarbamates proceeds smoothly with trialkylsilyl triflates  N,N,N',N'-tetramethylethylenediamine (TMEDA). Separation of the formed O-aryl N-isopropyl-N-trialkylsilylcarbamates from the byproduct TMEDA·HOTf, which is insoluble in diethyl ether or toluene, is not required. ortho-Lithiation with n-butyllithiumTMEDA at 78°C leads to the corresponding aryllithium, which does not undergo anionic ortho-Fries rearrangement under the reaction conditions, but is efficiently substituted by electrophilic reagents. During the aqueous work-up, the N-silyl group is removed and the corresponding ortho-substituted O-aryl N-isopropylcarbamate is isolated. Among the introduced electrophiles are: Me3Si, Bu3Sn, PhS, I, Br, Cl, alkyl, α-hydroxyalkyl. Liberation of the free phenols is performed under mild alkaline conditions.Key words: directed ortho-metalation, ortho-lithiated O-aryl carbamates, ortho-substituted phenols, in situ protection of N-monoalkylcarbamates.
Oxidative coupling of naphtho-9-crown-3 ether: X-ray crystal structure and solution and solid-state NMR analysis of the dimer
Authors: Buchanan G W , Rastegar M F , Yap G PA , Moghimi A , Ghandi M
Published: April 2011

Treatment of naphtho-9-crown-3 ether with FeCl3 and aqueous H2SO4 generates bis-naphtho-9-crown-3 ether in ca. 30% yield. This compound crystallizes in the monoclinic P21/n space group; a = 9.2004(9), b = 18.0868(17), and c = 13.2078(13) Å, β = 97.799(2)° and Z = 4. 1H and 13C NMR data have been obtained in solution, and the solid-state 13C NMR spectrum is included for comparison. A chemical shift range of ca. 12 ppm has been found for the oxygenated aliphatic carbons in the solid state, in contrast to the 3 ppm range in the solution 13C NMR spectrum. These results are discussed in terms of the torsional environments of the carbon sites in the crystal structure.Key words: crown ether, stereochemistry, oxidative dimerization.
Previously published / Prédémment paruAsymmetric total synthesis of (+)-exo-brevicomin based on enantioconvergent biocatalytic hydrolysis of an alkene-functionalized 2,3-disubstituted epoxide
Authors: Mayer Sandra F , Mang Harald , Steinreiber Andreas , Saf Robert , Faber Kurt
Published: April 2011

A short total asymmetric synthesis of (+)-exo- and ()-endo-brevicomin ((+)-exo-3 and ()-endo-3), which are components of the attracting pheromone system of several bark-beetle species belonging to the genera Dendroctonus and Dryocoetes, was accomplished via a chemoenzymatic protocol. The key step consisted of biocatalytic hydrolysis by bacterial epoxide hydrolases of cis-configured 2,3-disubstituted oxiranes bearing olefinic side chains. This reaction proceeded in an enantioconvergent fashion, by affording a single enantiomeric vic-diol from the rac-epoxide in up to 92% ee and 83% isolated yield.Key words: bacterial epoxide hydrolase, 2,3-disubstituted oxirane, enantioconvergent hydrolysis, (+)-exo-brevicomin, ()-endo-brevicomin.
Isolation and characterization of an unusually stable formamidinium-containing macrotricyclic complex of lithium ion formed during the synthesis of 14-thia-1,4,8,11-tetraaza-bicyclo[9,5,3]nonadecane
Authors: Barclay Tosha M , McAuley Alexander , Subramanian S
Published: April 2011

Using 1,3-bis(chloroacetamido)propane (5) as the common intermediate, an efficient route is described to the stepwise syntheses of 1-thia-4,8-diazacyclodecane, [10]aneN2S (8), and the pentadentate macrobicycle 17-thia-1,4,8,11-tetraazabicyclo[9,5,3]-nonadecane (11). During the investigation of the condensation of (5) with (8), with Li2CO3 used as a base the Li+ cation is carried over as the complex of the dioxo intermediate (10) and survives further reduction. Prolonged contact of these complexes with CHCl3 during cyclisation and extraction (in the presence of Li2CO3 and NaOH, respectively), leads to the formation of the complex cation [Li(4)]2+ as a byproduct in which the cationic macrocycle (4), containing a formamidinium ring, is formed through bridging of the 1,11-nitrogens in the macrobicycle (11) by a -CH= group that is derived from CHCl3. This renders the cavity in (4) too small for the inclusion of transition metal ions. Reaction of the lithium cation [Li(4)]2+ with PdCl2 yielded the trimetallic salt [(Li(4)]-PdCl2-[(Li(4)])](ClO4)4 in which two [Li(4)]2+ ions are bridged by a PdCl2 unit through coordination of the pendant thioether donors. A crystal structure of this trimetallic salt confirms the formation of [Li(4)]2+. In contrast, if triethylamine is used as a base during the cyclisation reaction leading to the formation of (11) and contact with aqueous NaOH and CHCl3 during its isolation is minimized, the formation of (4) is prevented and the yield of (11) improved.Key words: macrobicycle synthesis, lithium, formamidinium, paaladium, complex.
LINEAR FREE ENERGY RELATIONSHIPS CONCERNING REACTION RATES IN MODERATELY CONCENTRATED MINERAL ACIDS
Authors: Bunnett J. F. , Olsen Fredric P.
Published: April 2011

Linear relationships exist between log kψ + H0 (for reactions of weakly basic substrates) or log kψ (for reactions of strongly basic substrates) and (H0 + log [H+]). These are linear free energy relationships. For weakly basic substrates, the correlations obtained are better than in plots of (log kψ, + H0) versus log [Formula: see text] or of log kψ versus −H0. The slopes in plots of log kψ or (log kψ + H0), as appropriate, against (H0 + log [H+]) are taken as parameter, [Formula: see text], which characterizes the response of the reaction rate to changing mineral acid concentration. Values of [Formula: see text] for reactions of strongly basic substrates reflect only relationships between protonated substrate and transition state, and may be related to reaction mechanism. [Formula: see text] values for reactions of weakly basic substrates reflect both equilibrium protonation of the substrate and transformation of protonated substrate to transition state, and are therefore less directly related to mechanism. However, the [Formula: see text] values for the two steps are additive and that for the latter step can be obtained by subtraction if the overall [Formula: see text] value and that for equilibrium protonation are known.
SIMULTANEOUS ANALYSIS OF TWO-COMPONENT SYSTEMS BY DIFFUSE REFLECTANCE SPECTROSCOPY
Authors: Frei R. W. , Ryan D. E. , Lieu V. T.
Published: April 2011

Diffuse reflectance spectroscopy can be used for the analysis of multicomponent systems in the adsorbed state. The Kubelka–Munk theory for diffuse reflection and transmission on light-scattering layers has been applied for this analysis. Simple dye mixtures adsorbed on thin-layer chromatography-grade adsorbents were employed. The method can be adapted directly to the analysis of incompletely separated components on chromatographic adsorbents.
A CORRELATION OF STEPWISE STABILITY CONSTANT RATIOS AND SOME BONDING PROPERTIES OF TRANSITION METAL AND ZINC COMPLEXES
Authors: Manning P. G.
Published: April 2011

Stepwise stability constant ratios for some transition metal and zinc amino acid complexes are analyzed. It is shown that the observed ratios for Cu and Ni amino acid complexes are larger than the calculated ratios by a factor R, the Bjerrum rest effect. It is suggested that the rest effect is due to metal–nitrogen covalency, there being sufficient transfer of charge from ligand to metal in the first association stage to reduce markedly the electrostatic attraction between ligand and metal in the second.For Zn complexes, the observed and calculated ratios are in excellent agreement. A small rest effect would seem to be present in the Co system, but experimental errors render any conclusions uncertain.
Syntheses of novel substituted p-phenylenediamines
Authors: Oberster A. E. , Farhat Kelly , Kibler R. W. , Cook W. S. , Setoodeh S. Y. , Smith Jr. G. E. P.
Published: April 2011

The syntheses of 39 novel p-phenylenediamine derivatives are reported, including a number in which one of the nitrogens in the p-phenylenediamine is part of a heterocyclic ring. These compounds were prepared as part of a program seeking effective antiozone agents having little or no dermatitic toxicity.
The major reducing species operative when an equimolar proportion of AlCl3 is added over a short period of time to an ether solution of equimolar proportions of LiAlH4 and acetal or ketal
Authors: Diner U. E. , Davis H. A. , Brown R. K.
Published: April 2011

The relative ease of hydrogenolysis of ether solutions of acetals or ketals is much greater with AlH2Cl than with AlH3. Conversion of the species [Formula: see text] one into the other is fast, and is accomplished by the addition of the appropriate quantity of AlCl3 or LiAlH4 to solutions of AlH3 or AlHCl2, respectively. Gradual addition of an equimolar proportion of AlCl3 in ether to an ether solution of equimolar proportions of LiAlH4 and acetal or ketal first forms AlH3, which is rapidly converted into AlH2Cl as more AlCl3 is added. During the time of this addition (≤ 10 min) little reduction by AlH3 takes place. Most of the reduction is done by the species AlH2Cl when the AlCl3 is completely added.
Mono-O-(methylsulfonylethy)-d-glucoses
Authors: Bullock A. L. , Cirino V. O. , Rowland S. P.
Published: April 2011

Mono-O-(methylsulfonylethyl)-d-glucoses needed for comparison with the cleavage products obtained by acid hydrolysis of methyl vinyl sulfone modified cotton celluloses have been prepared. Several new glucose derivatives were prepared as intermediates in the synthesis of the desired 2-O-, 3-O-, and 6-O-(methylsulfonylethyl)-d-glucoses. The reactions were monitored by gas–liquid chromatography; use was made of trimethylsilyl derivatives as necessary. The substituted glucoses were obtained as glassy solids.
The pyrolysis of 3-vinyl-1-pyrazoline and 3-vinyl-1-pyrazoline-5,5-d2, and its relation to the vinylcyclopropane to cyclopentene rearrangement
Authors: Crawford Robert J. , Cameron Douglas M.
Published: April 2011

The kinetics and products of the pyrolysis of 3-vinyl-1-pyrazoline (1) are described. The pyrolysis of 3-vinyl-1-pyrazoline-5,5-d2(II) produces vinylcyclopropane-2,2-d2and cyclopentene-4,4-d2. The secondary isotope effect has been measured (kH/kD = 1.21 ± 0.03), and the reaction mechanism is interpreted as proceeding through a nitrogen-free intermediate similar to that suggested for the rearrangement of vinylcyclopropane to cyclopentene. At 170° a dramatic change in the product composition occurs, and evidence is presented for a "hot vinylcyclopropane" being produced.
Nuclear magnetic resonance studies. XI. Vinyl proton chemical shifts and coupling constants of some substituted styrenes
Authors: Gurudata  , Stothers J. B. , Talman J. D.
Published: April 2011

The proton spectra of the vinyl groups in a series of 23 substituted styrenes have been analyzed as ABC spin systems. The proton chemical shifts are compared with the previously reported shielding data for the corresponding vinyl carbon nuclei. The series includes 12 meta- and para-substituted examples and 10 ortho-substituted examples. The effects of steric inhibition of conjugation on the vinyl proton parameters for some 2,6-disubstituted derivatives are considered in detail.
Crystal structure of Cd2V2O7
Authors: Au P. K. L. , Calvo C.
Published: April 2011

Cadmium pyrovanadate crystallizes in the C2/m space group with lattice parameters a = 7.088(5) Å, b = 9.091(5) Å, c = 4.963(5) Å, β = 103°21(5)′, and z = 2. This crystal is an isostructure of the mineral thortveitite and thus the anion consists of a pair of centrosymmetrically related corner-sharing VO4 tetrahedra while the cation resides within a distorted octahedron of oxygen atoms. The anion has a linear V—O—V group, but, as with the isostructural pyrophosphates, the central oxygen atom shows an anomalously high thermal activity. The V—O bond distances are 1.76 Å for the inner bond and 1.70 Å for the terminal bond. The bond angles about the anion and cation are similar to those found for the other analogues of thortveitite.
Crystal structure of β-Zn3(PO4)2
Authors: Stephens J. S. , Calvo C.
Published: April 2011

β-Zn3(PO4)2 crystallizes in the monoclinic space group P 21/c with lattice parameters, a = 9.393(3) Å, b = 9.170(6) Å, c = 8.686(3) Å, β = 125.73(10)°, and Z = 4. The three independent cations are strongly ligated to 4, 5, and 5 oxygen atoms, with average Zn—O bond distances of 1.98 ± 0.09 Å, 2.10 ± 0.10 Å, and 2.08 ± 0.13 Å respectively. In addition there are two longer Zn—O distances of 2.51 Å and 2.55 Å in this structure. The PO4 groups exist as independent, nearly regular tetrahedra, with each oxygen atom ligated to two cations. Unlike the structures found for the α and γ phases of Zn3(PO4)2, which contain ribbons and sheets respectively as the basic cation coordination motif, the structure of β-Zn3(PO4)2 contains interconnected sheets.
Steroids and steroidases. VI. On the C-17 specificity of the Δ5-3-ketoisomerase of Pseudomonas testosteroni and evidence for substrate micelle formation
Authors: Jones J. Bryan , Wigfield Donald C.
Published: April 2011

Studies on the acid-, base-, and enzyme-catalyzed isomerizations of several variously C-17 substituted Δ5-3-ketosteroids have indicated micellar aggregation of relatively non polar substrates in the dilute aqueous methanol assay solvent to be an important consideration when evaluating specificity data. Further evidence that the isomerase is sensitive to the presence of 17α-substituents in its substrates has been obtained and the probability that tyrosine is the acid catalytic group at the active center is discussed.
Acid-catalyzed rearrangement of hydroperoxides. I. Benzhydryl hydroperoxides
Authors: Anderson Glenn H. , Smith James G.
Published: April 2011

Substituted benzhydryl hydroperoxides have been synthesized and rearranged using sulfuric acid as the catalyst and acetone as the solvent. The products have been analyzed in order to determine the migration aptitudes for the various aryl groups. A linear relationship exists between the log of the migration aptitude and the σ+ values of the substituents. Ortho substituents deviate from this relationship but the extent of deviation is much smaller than expected. The migration aptitude of hydrogen versus phenyl in the rearrangement of benzhydryl hydroperoxide has been found to vary markedly depending on the solvent. These observations and their bearing upon the mechanism of the rearrangement are discussed.
Acid-catalyzed rearrangement of hydroperoxides. II. Phenylcycloalkyl hydroperoxides
Authors: Anderson Glenn H. , Smith James G.
Published: April 2011

The acid-catalyzed rearrangement of 1-phenylcycloalkyl hydroperoxides has been investigated using the cyclohexyl, cyclopentyl, and cyclobutyl compounds. Evidence was sought for rearrangement of the cycloalkyl group in competition with migration of the phenyl group during the reaction. Such a rearrangement would result in ring expansion of the cycloalkyl group to give, ultimately, products formed by cycloalkyl ring opening.No evidence for such a reaction was found in the case of 1-phenylcyclohexyl hydroperoxide; only the expected products, phenol and cyclohexanone, were detected. However, rearrangement of 1-phenylcyclopentyl hydroperoxide gave, besides the expected phenol and cyclopentanone, significant amounts of the ring-opened compound 4-hydroxyvalerophenone as its acetate. A second product, 1-phenylcyclopentene, arose by elimination of hydrogen peroxide from the hydroperoxide.1-Phenylcyclobutyl hydroperoxide proved to undergo ring expansion with great facility. Only the ring expanded products, 2-phenyl-2-tetrahydrofuryl hydroperoxide and its corresponding peroxide, could be isolated in the treatment of 1-phenylcyclobutanol with hydrogen peroxide using catalytic amounts of mineral acids. However, in the absence of catalysts, 1-phenylcyclobutyl hydroperoxide was formed in detectable amounts and its presence was demonstrated by decomposition with ferrous sulfate to butyro-phenone and 1,6-dibenzoylhexane.It seems reasonable that ring strain is the factor promoting the ring expansion of 1-phenylcyclobutyl hydroperoxide. In the case of 1-phenylcyclopentyl hydroperoxide, it is suggested that the steric interaction of the ortho hydrogens of the phenyl group with the cyclopentyl ring protons has the effect of slowing the migration of the phenyl group sufficiently that alkyl migration can occur to give the observed ring-opened products.
Convenient synthesis of 3-amino-3-deoxy-D-ribose
Authors: Sowa Walter
Published: April 2011

3-Amino-3-deoxy-D-ribose and D-ribose were prepared from a derivative of D-xylose. 1,2-O-Isopropylidene-5-O-triphenylmethyl-α-D-xylofuranose (2) was oxidized by dimethyl sulfoxide – acetic anhydride to 1,2-O-isopropylidene-5-O-triphenylmethyl-α-D-erythro-pentofuranos-3-ulose (3). The oxime (4) of this 3-keto sugar derivative was reduced with lithium aluminium hydride to 3-amino-3-deoxy-1,2-O-isopropylidene-5-O-triphenylmethyl-α-D-ribofuranose (5), isolated as the acetamido derivative (6). Hydrolysis yielded 3-amino-3-deoxy-D-ribose hydrochloride. 3 was reduced by sodium borohydride to 1,2-O-isopropylidene-5-O-triphenylmethyl-α-D-ribofuranose (7), which yielded D-ribose on hydrolysis.
The preparation of methyl 4-deoxy-3-O-methyl-α,β-DL-threo-pentopyranoside
Authors: Sweet F. , Brown R. K.
Published: April 2011

Methyl 4-deoxy-3-O-methyl-α,β-DL-threo-pentopyranoside has been prepared by a highly selective reaction of methanol with cis-, trans-, or cis-trans-3,4-epoxy-2-methoxytetrahydropyran in the presence of a catalytic amount of.p-toluenesulfonic acid. The structure was supported by its conversion, after hydrolysis, to the phenylosazone and, by nitric acid oxidation, to O-methyl-DL-tartaric acid.
Hydrogen bonding in water and ice
Authors: Ford T. A. , Falk Michael
Published: April 2011

The absorption bands due to the OH and OD stretching vibrations of HDO in ice were measured between 0 and −182° and compared with the corresponding bands in liquid water. Their frequencies were correlated with the intermolecular potential energies of H2O and D2O. The distributions of the intermolecular energies in ice and in water at different temperatures were derived from the profiles of the bands.
Method for the accurate determination of specific rotation. Specific rotation of valine and leucine
Authors: MacDonald J. C.
Published: April 2011

The optical rotation of various concentrations of L-valine and L-leucine, dissolved in glacial acetic acid, or 5 or 6 M HCl, was measured with a photoelectric polarimeter at the nominal wavelengths 589, 578, 546, 436, and 365 nm and temperatures of 20, 25, and 30 °C. The specific rotation for any one wavelength, solute, and solvent could be defined by the equation [α]λT = A(1 + D(T − 25)) + BC, where T is temperature in °C, C is concentration in grams of solute per 100 ml of solution, and A, B, and D are constants. The best fit values of the constants were determined by computer calculation and are listed. Constants are also given for calculating a specific rotation based on grams of solute per 100 g of solution.
Synthesis of highly hindered diphenyl ethers
Authors: Neville George A. , Moir Robert Y.
Published: April 2011

A new modification of the Hems synthesis for diphenyl ethers is reported. The preparation of 11 tetra-ortho-substituted, 12 tri-ortho-substituted, and 4 di-ortho-substituted diphenyl ethers is described for the action of various phenols on N-(4′-carbomethoxy-2′,6′-dinitro)phenylpyridinium chloride. Some factors governing product formation are discussed on the basis of the extensive number of successful as well as unsuccessful reactions.
Anomalous acid-catalyzed reactions of cyclobutanones
Authors: Lee-Ruff Edward , Turro Nicholas J. , Amice P. , Conia J. M.
Published: April 2011

The reactions of 2(2-isopropanol)cyclobutanones with phosphorous pentoxide lead to ring opened carboxylic acids. Reaction of 2-isopropylidenecyclobutanones with polyphosphoric acid (PPA) gives ring cleavage rearrangement products. The mechanisms of these reactions are discussed in the light of the observed different reactions of the corresponding cyclopentanones.
Structures of bahia-I and bahia-II: two new guaianolides
Authors: de Vivar A. Romo , Ortega A.
Published: April 2011

Two new guaianolides bahia-I and bahia-II were isolated from Bahia pringlei. Their structures are shown to be 1a and 1b.
Etude de la décomposition des diazo-2 dicétones-1,3. II. Cas du diazo-2 diphényl-4,5 cyclohexanedione-1,3
Authors: Barker William D. , Gilbert Roland , Lapointe Jean-Paul , Veschambre Henri , Vocelle Daniel
Published: April 2011

not available
Synthesis of 8-deoxy-D-erythro-D-galacto-octose. Determination of the configuration of two octenoses
Authors: Lance D. G. , Szarek W. A. , Jones J. K. N. , Howarth G. B.
Published: April 2011

The preparation of 8-deoxy-1,2:3,4-di-O-isopropylidene-D-erythro-α-D-galacto-octopyranose (2) from two octenoses is described. The structure of 2 was established by degradation of its di-O-methyl derivative to 1-deoxy-2,3-di-O-methyl-L-erythritol. This work permits the assignment of configuration to the octenoses. Acid-catalyzed hydrolysis of 2 gave a new higher-carbon sugar, 8-deoxy-D-erythro-D-galacto-octose (4). The synthesis of 1-deoxy-2,3-di-O-methyl-L-threitol and 1-deoxy-2,3-di-O-methyl-D-erythritol is reported.
Synthesis of 3-deoxy-D-galacto-octulosonic acid
Authors: Perry M. B. , Webb Ann C.
Published: April 2011

3-Deoxy-D-galacto-octulosonic acid was prepared by oxidation of 3-deoxy-D-glycero-L-manno-octonic acid, and 3-deoxy-D-glycero-L-gluco-octonic acid made by the action of sodium cyanide on 2-deoxy-D-galacto-heptose. Gas–liquid chromatographic procedures for the detection and quantitative analysis of the 3-deoxy-D-galacto-octulosonic acid are described.
Spin trapping with 9-nitrosotriptycene
Authors: Kaur Harparkash , Perkins M John , Scheffer André , Vendor-Morris David C
Published: April 2011

Nitrosotriptycene is found to be a potentially useful spin trap when used in organic solvents; the esr spectra of its spin adducts are simple, but they may show marked temperature dependence due to restricted rotation. Nitrosotriptycene traps primary alkyl radicals with a rate constant of ca. 2 × 107 L mol−1 s−1 at 40°C in benzene.
The He(I) photoelectron spectra of the propenoyl halides
Authors: Klapstein Dieter , O'Brien Robert T.
Published: April 2011

The He(I) photoelectron spectra of propenal and the propenoyl halides, CH2=CHCOX, X = H, F, Cl, Br, were measured and interpreted with the aid of semi-empirical MO calculations, comparison with results for structurally related species, and a sum-rule for the out-of-plane orbital energies. Information concerning the identities and relative energies of the higher occupied molecular orbitals of the neutral molecules could be deduced from the spectra.
The fast atom bombardment mass spectra of some N-substituted pyrimidinium salts
Authors: Kazakoff Clement W. , Rye Robin T. B. , Tee Oswald S.
Published: April 2011

The fast atom bombardment mass spectra of selected 1,2-dihydro-1,3-disubstituted-2-oxo-pyrimidinium salts are presented. Loss of N-substituents from the solute cation is the principal fragmentation observed in the positive ion spectra. Several concentration dependent features of the spectra are identified; these are thought to result from the interaction of the solute cation with bombardment-induced matrix fragments. Cluster ions are observed in both positive and negative ion spectra. In a mixed solute system cluster ions resulting from extensive cation and anion mixing are observed; the concentration dependence of these mixed cluster ion peaks can be approximately described in terms of conventional solution equilibria.
The chemistry of the blue stain fungi. Part 3. Some metabolites of Ceratocystisminor (Hedgcock) Hunt
Authors: Ayer William A. , Attah-Poku Samuel K. , Browne Lois M. , Orszanska Helena
Published: April 2011

The metabolites formed in still cultures by Ceratocystisminor, one of the fungal species associated with the blue stain disease of pine, have been isolated and identified as ceratenolone (5), 6,8-dihydroxy-3-methylisocoumarin (2), 8-hydroxy-6-methoxy-3-methylisocoumarin (8), 3,4-dihydro-6,8-dihydroxy-3-methylisocoumarin (10), 3,4-dihydro-3-methyl-3,6,8-trihydroxy-3-methylisocoumarin (12), 3,4-dihydro-3-methyl-3,4,6,8-tetrahydroxyisocoumarin (13), and succinic acid. Ceratenolone (5), a new type of natural product, forms an intensely blue chelate with ferric ions. This chelate may be responsible for the blue coloration of the wood of pine infected by Ceratocystisminor.
Étude des mélanges eau–HF par spectroscopie infrarouge à transformée de Fourier
Authors: Khorami Jaleh , Beaudoin Réjean , Ménard Hugues
Published: April 2011

An analysis of the ir spectra of HF–H2O mixtures containing from 10 to 97% of HF has been used to determine the evolution of the ionic species of HF. The results indicate that water and the ions H3O+F−, H3O+, and F− are present in the solutions containing less than 46% w/w of HF. In the solutions containing at least 50% w/w of HF, bands characteristic of the ion HF2− start appearing and their intensity increases with the concentration of HF, up to a concentration of 90%. As well, polymers of (HF)n have been detected in the solutions containing the highest concentration of HF. These results can be used to explain the electrochemical behaviour of solutions of HF–H2O.
Kinetics and mechanisms of oxidation of methylamine by permanganate ion
Authors: Mata-Perez Fernando , Perez-Benito Joaquin F.
Published: April 2011

The oxidation of methylamine by permanganate ion in aqueous phosphate buffers is autocatalyzed by a soluble form of colloidal manganese dioxide temporarily stabilized in solution by adsorption of phosphate ions on its surface. The dependence of the rate constants of both the noncatalytic and catalytic mechanisms on the concentrations of both methylammonium and hydroxyl ions and on temperature has been determined. The activation parameters have been obtained. Mechanisms in agreement with the experimental data are proposed.
Enzymes in organic synthesis. 37. Preparation and characterization of potential decalindione substrates of horse liver alcohol dehydrogenase
Authors: Jones J. Bryan , Dodds David R.
Published: April 2011

The preparations of ten decalindiones for investigation as substrates of horse liver alcohol dehydrogenase are reported. The structure characterizations include clarifications of some ambiguities in the decalin literature.
Allomerization of cholic acid and conversion to petromyzonol
Authors: Zhu Xingpei , Amouzou Etchri , McLean Stewart
Published: April 2011

Petromyzonol, a rare bile substance, has been prepared from an abundant starting material, cholic acid. The critical conversion, the inversion of the configuration at C-5, was accomplished by oxidizing a suitably protected derivative of cholic acid to a 1,4-dien-3-one, which was then stereoselectively reduced to methyl allocholate. In a single oxidation step, the 3-hydroxy steroid was converted to the dienone by Barton's procedure using a catalytic amount of benzeneseleninic anhydride and m-iodoxybenzoic acid as the stoichiometric oxidant. The stereoselective reduction employed two steps: hydrogenation of the dienone to the saturated ketone (5α) in the presence of the Wilkinson catalyst, followed by reduction of the ketone with K-Selectride. Finally, methyl allocholate was reduced to petromyzonol with lithium aluminum hydride.