bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluorosulfates of palladium
Authors: Lee K. C. , Aubke F.
Published: May 2006

The syntheses of Pd(SO3F)2 and Pd(SO3F)3 by the reactions of palladium with BrOSO2F and S2O6F2 are described. Structural information on both compounds is based on infrared, Raman, diffuse reflectance, and electronic mull spectra as well as magnetic measurements from ∼300 to ∼100 K. Palladium bisfluorosulfate is found to have a polymeric structure with the fluorosulfate group acting as a tridentate ligand. As a consequence, an octahedral environment is found for Pd2+ with a 3A2g ground state, a µeff298 value of 3.39 BM and the ligand field parameter Dq = 1177 cm−1 and B = 633 cm−1. Pd(SO3F)3 is best regarded as PdII[PdIV(SO3F)6].
3β-Azidoformate thermolysis as a method for functionalizing the 4α-methyl group of lanostan-3β-ol and similar systems
Authors: Alewood Paul Francis , Benn Michael , Wong John , Jones Alan J.
Published: May 2006

Thermolyses of the azidoformate derivatives of 1,1,4a-trimethyl-trans-decalin-2β-ol, lanostanol-3β, and Δ8-lanosten-3β-ol yield the perhydro-1,3-oxazin-2-one products of nitrene insertion into the adjacent α-oriented methyl groups, as well as oxazolidinones and ketones.
Ammonium fluorolanthanates: solid state synthesis, infrared spectral and X-ray diffraction data
Authors: Rajeshwar Krishnan , Secco Etalo A.
Published: May 2006

Solid state synthesis of thirteen ammonium fluorolanthanates is reported. Two main types of fluorolanthanates appeared in the primary synthesis reaction, viz. NH4LnF4 and (NH4)3Ln2F9.The final decomposition product of the fluorolanthanates is LnF3 with NH4Ln2F7 appearing as an intermediate in (NH4)3Ln2F9 decomposition.Infrared absorption spectra and X-ray diffraction data for the stable fluorolanthanates are presented.
Simple electrochemical synthesis of vanadium(II) halides
Authors: Habeeb Jacob J. , Neilson Lynn , Tuck Dennis G.
Published: May 2006

Vanadium metal dissolves rapidly in a cell Pt/X2 in CH3CN/V (anode) (X = Cl, Br, I) under applied voltages of 5–50 V. The solution phase yields crystalline VCl2. 2CH3CN, VBr2. CH3CN, or VI2; the acetonitrile adducts decompose to VX2 on heating in vacuo. Overall yields of VX2, based on weight of metal dissolved, are 80–90%.
Nuclear analogs of β-lactam antibiotics. IV. Synthesis of 1-oxo-Δ3-O-2-isocephems
Authors: Doyle Terrence William , Martel Alain , Luh Bing-Yu
Published: May 2006

The synthesis of 7-β-phenoxyacetamido-3-methyl-1-oxo-Δ3-O-2-isocephem-4-carboxylic acid 14 is described. Condensation of amine 2 followed by β -lactam formation and ozonolysis gave the acid 5. This was converted to its trichloroethyl ester 8 and the ketal was hydrolyzed to give 9. Reduction of the azido function followed by amide formation gave 11. The trichloroethyl group was removed and the enol acid 12 closed to yield 13. Hydrogenolysis of the benzyl ester gave 14. The structural assignments to the compounds are discussed.
Nuclear analogs of β-lactam antibiotics. VI. Synthesis of N-2-isocephems
Authors: Doyle Terrence William , Luh Bing-Yu , Chu Daniel Tim-Wu , Belleau Bernard
Published: May 2006

The syntheses of N-methyl and N-carboethoxy-7-β-phenoxyacetamido-Δ3-N-2-isocephem-4-carboxylic acids 17a and 17b are reported. Treatment of aldehyde 3c with methylamine followed by reduction of the Schiff base gave 4d which was converted to its trifluoroacetamide 5c. Acid catalyzed elimination of a mole of ethanol from 5c, gave 8b which was converted to the enol 10b via the vinylogous pyrrolidino amide 9b. Reductive removal of the trifluoroacetamide function led to spontaneous ring closure to give 11b. Alternatively treatment of bis-mesylate 12b with ammonia or methylamine gave 13a and 13b, respectively. Treatment of 13b with sodium hydride in DMSO gave 11b. Attempted acylation of 13a gave 14. Reduction of the azido functions in 11b and 14 followed by coupling of the amines to phenoxyacetic acid and reductive removal of the benzyl esters gave 17a and 17b, respectively. The structural assignments are discussed.
N-Nitromethylphthalimide. A formyl anion equivalent
Authors: Cowherd Frank G. , Doria Marie-Carmen , Galeazzi Edvige , Muchowski Joseph M.
Published: May 2006

It is shown that the exclusive 1,4-addition of N-nitromethylphthalimide 4a to unhindered α,β-unsaturated ketones and esters can be effected by non-nucleophilic bases, such as sodium hydride or potassium fluoride, in dimethyl sulfoxide. The phthalimido moiety can be removed from the adducts with hydroxylamine or 1,2-dianilinoethane to give the oximes or diphenylimidazolidines of 1,4-ketoaldehydes. The ethylene ketal 5 of 3-formylcyclohexanone could easily be recovered from the imidazolidine 10, but it was not possible to transform 11 into 3-formylcyclohexanone under similar conditions. It is further shown that reactions, such as the Knoevenagel condensation, or the Paal–Knorr synthesis of pyrroles, can be achieved directly on the adducts without the need for isolating the unstable 4-formyl carbonyl compounds. N-Nitromethylphthalimide thus serves as a new formyl anion equivalent.
Reaction of xenon difluoride. Part III. Oxidative-fluorination and α-fluorination of sulfur(II) compounds
Authors: Marat Ronald Kirk , Janzen Alexander F.
Published: May 2006

The reaction of XeF2 with aryl and alkyl sulfides and thiols has been investigated. Oxidative-fluorination of diphenyl sulflde and tert-butylphenyl sulfide gives diphenylsulfur difluoride and tert-butylphenylsulfur difluoride, respectively. The presence of an α-hydrogen substituent leads to α-fluorination and, in some cases, to olefin formation while reaction of XeF2 with thiols gives disulfldes. HF catalyzed decomposition of products and intermolecular fluorine exchange is inhibited by the addition of [(CH3)3Si]2NH.On a étudié la réaction de XeF2 avec des sulfures et des thiols d'aryles et d'alkyles. La fluoration oxydative du sulfure de diphényle et du sulfure de tert-butylphényle conduisent respectivement au difluorure de diphénylsulfure et au difluorure de tert-butylphénylsulfure. La présence d'un hydrogène comme substituant en α conduit à une α fluoration et dans quelques cas à la formation d'oléflne; la réaction de XeF2 avec les thiols conduit aux disulfures. La décomposition catalysée par HF des produits et l'échange intermoléculaire du fluorure sont inhibés par l'addition de [(CH3)3Si]2NH. [Traduit par le journal]
Organic electrode processes: generalized reduction mechanisms
Authors: Elving Philip J.
Published: May 2006

Prototype formulations are considered for the reaction pathways commonly encountered for the electrolytic reduction of organic compounds in aqueous and nonaqueous media on the basis that the essential feature is severance of a chemical bond which requires transfer into the reaction site of one or two electrons; multiple electron processes result from instability at the applied potential of initially produced species or their chemically altered products. To obtain electrical neutrality, uptake of electrons may have to be accompanied by that of a cation, generally a proton. Pertinent factors in the path followed in the overall electrode process may include a sequence of free radical or radical anion going to dimeric or carbanion species (depending on the relative rates of chemical and charge-transfer steps), possible interaction of intermediate products with their progenitors, proton donor activities, medium properties (e.g in respect to rates of chemical reactions accompanying charge-transfer and control of the chemical states of reactants and intermediates), stereochemical factors inherent in reactant and intermediate species, and chemical interaction with the electrode material. Application of the general mechanistic considerations are illustrated by various types of electrolytic reductions: aromatic hydrocarbon, nitrogen heterocycle, carbon–halogen bond, ketone carbonyl group, and beta halogenated and/or unsaturated acids.
Tricarbonylferrole iron tricarbonyl derivatives: formation from thiophenes and iron atoms in a CO atmosphere and fluxional behaviour
Authors: Chivers Tristram , Timms Peter L.
Published: May 2006

Co-condensation of metal atoms (Cr, Fe) with thiophenes [Formula: see text] (R = R′ = H, Me; R = H, R' = Me) at −196 °C leads to desulphurization of the thiophene. Warm-up of the iron–thiophene co-condensate in a CO atmosphere produces derivatives of tricarbonylferrole iron tricarbonyl, C4H2RR′Fe2(CO)6. 13C nmr studies of these complexes show that the tricarbonyl ferrole unit is static from −95 °C to +60 °C, while the π-Fe(CO)3 group exhibits fluxional behaviour. Addition of dienes or Me3P in hexane to the iron–thiophene co-condensate at −196 °C yields thermally unstable red solutions on melting.
Homogeneous catalysis of deuterium transfer by potassium hydroxide and potassium methoxide D2–H2O and D2–CH3OH exchange
Authors: Strathdee Graeme G. , Garner David M. , Given Russell M.
Published: May 2006

The kinetics and mechanism of exchange of deuterium between D2 and water and between D2 and methanol, catalyzed respectively by concentrated potassium hydroxide and potassium methoxide, has been studied between 348 and 398 K. In the D2–KOH–H2O case, the transfer of deuterium was found to be controlled by the rate of activation of the D2 molecule by OH−. Rapid exchange of D+ with the aqueous solution followed. From the D2–KOCH3–CH3OH studies, it was concluded that deuterium exchange depended upon the rates of both D2 activation by methoxide and interaction of the solvent with the transition, or encounter, complex. The dependence of second-order rate constants on solvent activity for both systems was determined by normalization of the exchange reaction rates to unit reagent activity. Analysis of the kinetic isotope effects for each system suggested that their increase with base concentration or temperature was due to solvation effects.
Stereochemical basis of anticonvulsant drug action. VI. Crystal and molecular structure of diphenylsilanediol
Authors: Fawcett J. Keith , Camerman Norman , Camerman Arthur
Published: May 2006

The crystal and molecular structure of diphenylsilanediol, a compound with recently demonstrated anticonvulsant activity, has been determined and its stereochemistry compared with other antiepileptics. Crystals of diphenylsilanediol are triclinic, space group [Formula: see text] with cell dimensions a = 9.912, b = 15.048, c = 14.519 Å, α = 120.83,β = 99.95, γ = 100.84°, Z = 6 molecules per cell (3 molecules per asymmetric unit). The structure was determined by Patterson and Fourier methods and refined to a final discrepancy value R = 0.034. The phenyl ring planes in the molecule are rotated by 80° with respect to each other, and the hydroxyl oxygen atoms are 2.66 Å apart. The molecular parameters help to delineate limits of stereochemical variation in these molecules with retention of anticonvulsant activity.
Potential affinity and photoaffinity reagents for the membrane protein of human erythrocytes involved in glucose transport. Synthesis of 6-amino-6-deoxy derivatives of D-glucose
Authors: Ramjeesingh Mohabir , Kahlenberg Arthur
Published: May 2006

From 1,2-O-isopropylidene-α-D-glucofuranose 1, the 6-amino-6-deoxy-l,2:3,5-di-O-isopropylidene-α-D-glucofuranose 6 was prepared in a four-step sequence in an overall 50% yield. The conversion of 6 to the 6-bromoacetamido-6-deoxy 10, 6-deoxy-6-isothiocyanato 11, and 6-(p-azido-o-nitroanilino)-6-deoxy 12 derivatives of D-glucose is described.
Modified MacInnes equation
Authors: Poh Bo-Long
Published: May 2006

A modified Maclnnes equation is presented and its relationships with Taft and Br0nsted equations discussed.
Interactions solutés–solvants dans les mélanges eau – alcool tert-butylique. VIII. Volumes molaires apparents des benzoates halogéno-substitués
Authors: Dollet Nicole , Avedikian Levon , Juillard Jean
Published: May 2006

Apparent molal volumes of potassium salts of para-substituted (—F, —Cl, —I, —CH3) and unsubstituted benzoic acids in water – tert-butyl alcohol mixtures (0–40% by weight) are reported. Large volume changes are observed in media rich in water. Substituents size effects on both the location and the amplitude of the volume maxima are discussed in terms of the structure of the mixed solvents.
Réactions avec le diazométhane d'esters cinnamylidène maloniques ou cyanacétiques méthylés ou phénylés en γ des groupements fonctionnels et des malononitriles correspondants. Thermolyse des pyrazolines obtenues
Authors: Martelli J. , Carrié R.
Published: May 2006

The syntheses of cinnamylidene malonic or cyanacetic esters, bearing a methyl or a phenyl group in the position γ to the withdrawing groups, were achieved. The configurations of the various isomers were established and the conformations are discussed. Diazomethane adds exclusively to the α,β double bond of these dipolarophiles in only one orientation. The thermolysis of the resulting 1-pyrazoline was studied.
Synthetic applications of the photochemically induced addition of oxycarbinyl species to α-enones. Part II. The addition of ketals, aldehydes, and polyfunctional species
Authors: Fraser-Reid Bert , Anderson Robert Charles , Hicks David Roy , Walker David Louis
Published: May 2006

Alcohols possessing an α-hydrogen, acetals, and aldehydes undergo photochemically induced conjugate addition to a variety of α-enones to give 1,4-ketols, 1,4-keto ketols and 1,4-diketones respectively. It appears that the aldehydes frequently succeed where acetals and alcohols fail, and acetals where alcohols fail. It is therefore possible to employ polyfunctional addenda and achieve addition at only one of the activated sites. The reactions are always regiospecific and are frequently completely stereoselective.
Synthetic routes to 2′,3′-cyclopropanated and 2′,3′-unsaturated nucleosides
Authors: Tam Steve Yik-Kai , Fraser-Reid Bert
Published: May 2006

Cyclopropyl glycopyranosides which solvolyze via a stabilized cyclopropyl carbinyl-oxocar-bonium ion react under neutral conditions with nucleoside bases in nitromethane at 200 °C to give good yields of the corresponding cyclopropanated nucleosides. Under similar conditions hex-2-enopyranosides (which solvolyze by allyl-oxocarbonium ions) do not react. However, under catalysis by mercuric bromide or acetic acid, the corresponding 2′,3′ unsaturated nucleosides are formed although accompanied by appreciable amounts of 1′,2′-unsaturated-3′-nucleosides. Formation of the latter may be avoided if the hex-2-enopyranosides are first converted to the hex-2-enopyranosyl acetates by treatment with boron trifluoride and acetic anhydride. The derived acetates react with the nucleoside bases without catalysis to give anomeric mixtures of nucleosides, there being no trace of the unwanted 3′-nucleosides.
Isolation of intermediates in the rearrangement of 4-cyano-4,5-dihydroazepines to furo[2,3-b]pyridine derivatives
Authors: Gregory Brian , Bullock Eric , Chen Teng-Song
Published: May 2006

4-Cyano-4,5-dihydroazepines, when treated with an acidic ion-exchange resin in aqueous alcohol, undergo hydrolytic cleavage to a cyanooctanedionediester. The cyanooctanedione-diester and its thermal cyclization product, a 4,7-dihydrofuro[2,3-b]pyridine, are shown to be intermediates in the rearrangement of cyanodihydroazepines to furo[2,3-b]pyridines by aqueous alcoholic silver nitrate. The mechanism of this rearrangement and the role of silver(I) are discussed. Ethyl 2-(2-cyanoethyl)acetoacetate cyclizes to a 1,2,3,4-tetrahydro-2-oxopyridine when refluxed with silver nitrate in aqueous ethanol.
Preparative synthesis of 1-deoxy-D-erythro-2-pentulose and some of its derivatives
Authors: Fischer Jean-Claude , Horton Derek , Weckerle Wolfgang
Published: May 2006

Methyl 4,6-O-benzylidene-2-deoxy-α-D-erythro-hexopyranosid-3-ulose (1) was converted, by means of lithium hydroxide in a two-phase system, into 3,5-O-benzylidene-1-deoxy-keto-D-erythro-2-pentulose (2) in 55% yield. Compound 2 was further characterized as its (2,4-dinitrophenyl)hydrazone 3, its 4-acetate 4, and the 4-benzoate 5. The configurational assignment for the corresponding pentitol derivatives (6 and 8) of 2 was achieved by 1Hmr analysis of the cyclic carbonates 11 (from 6) and 13 (from 8) and confirmed by comparing the physical constants of the 1-deoxypentitols having the D-ribo (12) and D-arabino (14) configurations with literature data. Hydrolysis of 2 with mild acid afforded the title ketose (9) as a syrup that gave a crystalline (2,4-dinitrophenyl)hydrazone (10), and an acyclic triacetate (15) as an oil. A mechanism for the chain degradation of compound 1 to give 2 is proposed.
The competitive scissions of cycloalkane oxiranes by charged and neutral nucleophiles in acidic aqueous methanol
Authors: Bovenkamp John W. , Moir Robert Y. , Bannard Robert A. B.
Published: May 2006

Six related oxiranes (the cis and trans isomers derived from 3-methoxycyclopentene and from 3-methoxycyclohexene, as well as the oxiranes from the corresponding unsubstituted olefins) were each treated under the same conditions with an acidic solution containing charged and uncharged nucleophiles (chloride ion, water, and methanol). The corresponding perchloric acid catalyzed scissions were also carried out. Accurate and reproducible methods of product analysis for the reaction mixtures were developed. In this way, nucleophilic attacks upon different oxiranes were compared directly. Attacks by different nucleophiles upon the same oxirane, or by a single nucleophile upon different positions of the same oxirane, were compared in the very same solution. The results are considered to provide the most extensive demonstration of the effects of charge orientation yet available. The synthesis of some new isomeric 1,2,3-trisubstituted diols and dimethoxyalcohols are reported.
Phase-transfer catalyzed formation of cyanohydrin ethers and acetates
Authors: McIntosh John M.
Published: May 2006

In the presence of an allylic bromide, aldehydes, but not ketones, react with cyanide ion under phase-transfer catalysis to give cyanohydrin allyl ethers which can be converted to ketones. Other alkylating agents and nucleophiles give different results. Replacing the allylic bromide with acetic anhydride leads to cyanohydrin acetates.
Crystal and molecular structure of hexamethylcyclotriphosphazene, (NPMe2)3
Authors: Oakley Richard T. , Paddock Norman L. , Rettig Steven J. , Trotter James
Published: May 2006

Crystals of hexamethylcyclotriphosphazene are monoclinic, a = 12.084(2), b = 13.426(1), c = 15.488(2) Å,β = 102.92(2)°, Z = 8, space group C2/c. The structure was solved by direct methods and was refined by full-matrix least squares procedures to a final R of 0.045 and Rw of 0.060 for 1922 reflections with I ≥ 3σ(I). The six-membered phosphazene ring is slightly nonplanar and has a distorted chair conformation. Important molecular dimensions (bond lengths are corrected for libration) are: P—N, 1.599(2)–1.612(2), P—C, 1.796(3)–1.823(4) Å, N—P—N, 115.7(1)–117.9(1), P—N—P, 122.1(1)–122.9(1), and C—P—C, 101.8(2)-103.1(2)°.
Kinetics of flowing dispersions. X. Oscillations in optical properties of streaming suspensions of spheroids
Authors: Okagawa A. , Mason S. G.
Published: May 2006

Transients in angular light scattering and turbidity of dilute suspensions of nearly monodisperse spheroidal particles undergoing simple shear flow have been investigated by combining Rayleigh–Debye light scattering theory for single dielectric particles with fluid mechanical theory for the orientation distributions of particle assemblies in shear flow. Applying shear to an initially isotropic suspension causes the orientation distributions and thus the angular scattering coefficients to oscillate. Various geometrical arrangements are considered with a view to selecting those that will maximize such rheo-optical effects.By calculating the optical scattering cross section of a single particle, the turbidity of a suspension is obtained; like the scattering coefficient, it undergoes oscillations that are damped by (1) the inevitable spread in particle shape and volume in real systems, (2) shear-induced particle interactions, and (3) rotary Brownian motion. The rates of damping, expressed as relaxation times, are considered for the three mechanisms acting alone or in concert.Preliminary measurements of the turbidity of dilute suspensions of hardened human red blood cells confirm this general pattern of behavior. Apart from their intrinsic interest, such rheo-optical effects can be used to determine a number of useful properties of dispersions.
Mercury photosensitized decomposition of thietane
Authors: Dice David R. , Steer Ronald P.
Published: May 2006

The mercury photosensitized decomposition of thietane vapour at room temperature has been studied. Quantum yields of the products, ethylene, propylene, cyclopropane, 1,2-dithiocane, and 1,5-hexadiene, have been measured as a function of substrate pressure, percent decomposition, and intensity and the influence of added NO and propylene has been examined. At low pressures quantum yields of thietane decomposition exceed unity. A mechanism involving thiatrimethylene and 4,5-dithiahexamethylene biradicals is proposed.
Preparation of substituted 2,3-diphenylindoles and 2,3-diphenylindolenyl-3-hydroperoxides via reduction of α-(o-nitrophenyl)deoxybenzoins
Authors: Jawdosiuk M. , Kmiotek-Skarżyńska I. , Wilczyński W.
Published: May 2006

Substituted o-nitrohalobenzenes react in aprotic solvents in the presence of powdered potassium hydroxide with deoxybenzoin to form corresponding nitroarylated deoxybenzoins. The latter on reduction form substituted 2,3-diphenylindoles which under certain conditions undergo oxidation with atmospheric oxygen to form 2,3-diphenylindolenyl-3-hydroperoxides.
Preresonance Raman spectra and excitation profiles of some chemically and isotopically substituted trans-4-benzylideneoxazolin-5-ones
Authors: Phelps D. J. , Carriere R. G. , Kumar K. , Carey P. R.
Published: May 2006

Resonance and preresonance Raman spectra of nine substituted trans-4-benzylidene- Δ2-oxazolin-5-ones are reported. The seven analogs with phenyl in the 2 position of the oxazolinone ring have either an electron donating or attracting group on one of the phenyl rings. Although shifts in λmax of up to 100 nm are observed the Raman spectra are very similar to that of the unsubstituted trans isomer. However, in the substituted compounds modes from the benzylidene portion may become weakly intensity enhanced. Replacing the 2-phenyl group by 2-methyl in the oxazolinone ring results in quite gross changes in the Raman spectrum. Substitution by 15N in the ring of a 2-methyloxazolinone reveals that a change in the vibrational coupling scheme occurs. Excitation profiles for the 2-phenyl and the 2-methyl analogs of 4-(p-nitrobenzylidene)oxazolinone indicate that in each compound ail intensity enhanced modes are coupled to the intense low energy absorption band near 350 nm and the intensity enhancement fits the FB2 terms of Albrecht and Hutley. However, differences in the relative intensity of the benzylidene nitro feature in the 2-methyl and 2-phenyl analogs, taken with the excitation profiles, suggest that in the 2-methyl compound the electronic transition responsible for Raman intensity enhancement is no longer primarily located in the C=C—N=C—Ph moiety.
Photolysis of 1,2-dipropyl-3,5-diethyl-1,2-dihydropyridine. A model for some elastin cross-links
Authors: Guay Mireille , Lamy François
Published: May 2006

Photolysis of 1,2-dipropyl-3,5-diethyl-1,2-dihydropyridine 4, at λ > 300 nm, results in the opening of the ring to give an iminodiene 5, which upon reduction leads to an aminodiene 6. The imine 5 releases propylamine at acid pH. The dihydropyridine 4 is a model for analogous dihydro compounds which cross-link polypeptide chains in elastin. Thus photolysis would seem to be a specific method for breaking this type of cross-link in the insoluble fibrous protein.
The electrochemical formation of mercuric oxide in alkaline solution
Authors: Barradas Remigio Germano , Fletcher Stephen , Porter John Douglas
Published: May 2006

The electrochemical formation of mercuric oxide on mercury in alkaline solutions is described. The reaction was investigated because of its importance as a reference electrode system, and also because it provides a model test of recent theoretical developments. Various derived data are compared to computer simulations of the growth mechanism.
Cyclopropanediols. VII. Comportement chimique des cyclopropanediols et reactions de bis(trimethylsiloxy)-1,2 cyclopropanes
Authors: Goaller Raymond Le , Pierre Jean-Louis
Published: May 2006

The chemical behaviour of 1,2-bis(trimethylsiloxy)cyclopropanes is described. Acid and base solvolyses as well as reactions with chlorine and bromine occur with opening of the ring leading to α-ketols, enones and β-diketones. Ketols and enones arise from a cyclopropanol type ring opening while the β-diketones resuit from the oxidation of the intermediate siloxycyclopropanols or cyclopropanediols. [Journal translation]
Preparation of cyclobutenones and cyclopent-2-enones via epoxy sulfone cyclizations
Authors: Corbel Bernard , Decesare John M. , Durst Tony
Published: May 2006

Epoxysulfones of the type [Formula: see text] react with about 2 equiv. of CH3MgI in THF to give 3-phenylsulfonylcyclobutanols and 3-phenylsulfonylcyclopentanols in good to excellent yields. 3-Alkyl-3-phenylsulfonylcyclobutanols and -cyclopentanols can be obtained either from the appropriately substituted epoxides or by alkylation of the dianion of the parent 3-phenylsulfonylcycloalkanols. Oxidation of these alcohols with Jones' reagent followed by treatment of the crude ketones with triethylamine leads to 3-substituted cyclobutenones and cyclopent-2-enones.
Crystal structure of methyl,2-mercaptopyrimidinatomercury(II)
Authors: Chieh Chung
Published: May 2006

Methyl,2-mercaptopyrimidinatomercury(II) was synthesized from methylmercuric hydroxide and 2-mercaptopyrimidine in aqueous solution. The crystal is orthorhombic with a = 4.063(2), b = 9.901(4), c = 18.808(15) Å, Dm = 2.88(1), Z = 4, Dc = 2.867 g cm−3, space group P212121. The structure was solved by the heavy atom method using 605 diffractometer measured reflections. The final R factor was 0.069. The key bond lengths and angles are: Hg—S, 2.39(2) Å, Hg—CH3, 2.13(6) Å, [Formula: see text] 174°. The CH3HgS— group bends out of the plane of the pyrimidine ring and the Hg atom interacts rather strongly with one of the ring nitrogens with an Hg—N distance of 2.83 Å. However, the Hg … N interaction is very labile in solution, since the two hydrogen atoms in the meta positions are equivalent from the 1H nmr spectra in both CDCl3 and DMSO solutions. The solution of the compound is not optically active.
The effect of the variation of potential on progressive three-dimensional nucleation and growth
Authors: Fletcher Stephen , Smith Arthur
Published: May 2006

The effect of varying the applied potential during progressive three-dimensional nucleation and growth is described. The assumed model is that due to Armstrong, Fleischmann, and Thirsk in which expanding nuclei are considered to be right circular cones distributed at random on the electrode surface. The present work extends the previous potentiostatic approach by considering that the electrode surface coverage function responds instantaneously to small changes of applied potential. Under these circumstances we show that it is possible to calculate in an exact way the theoretical response of the model to various applied potential waveforms. In particular, the linear potential sweep and the staircase potential ramp are considered, as well as feedback loops generated by uncompensated ohmic overpotential. Certain limiting cases are derived which may be tested by experiment.
Application de la spectrométrie ir et Raman à l'étude des complexes en solution aqueuse–Be2+–H2C2O4
Authors: Jaber M. , Bertin F. , Thomas-David G.
Published: May 2006

A study of solutions of the oxalate complexes of berylium by ir and Raman spectrometry has demonstrated the formation of three complexed species: BeC2O4, Be(C2O4)22−, and Be3(OH)3(C2O4)33− regardless of the ratio used. Each complex is characterized by specific vibrational frequencies which are independant of the pH of the solution. It was possible to determine the concentration of each species as a function of pH, as well as its stability constant, by measuring the intensifies of certain characteristic bands in the Raman scattering spectrum. [Journal translation]
The chemistry of 2-methyltetrahydropyran-4-one: An L-Selectride reaction that gives predominantly the equatorial alcohol
Authors: Wigfield Donald C. , Feiner Steve
Published: May 2006

The stereoisomers of 2-methyltetrahydropyran-4-ol have been separated and identified by carbon-13 and proton nmr analysis of the trideuteriomethyl-2,6,6-trideuterio analogue. Stereoisomeric product ratios of reduction of 2-methyltetrahydropyran-4-one (1) by NaBH4, KBH4, L-Selectride, K-Selectride, and LiBH(nBu)3 have been determined and compared with reductions of 3-methylcyclohexanone. Product ratios in the reduction of the two substrates by the borohydride reducing agents are similar but are quite different in the reduction by the Selectride reducing agents, 1 being reduced by Selectride to give 73% equatorialalcohol. Two possible mechanisms of reduction of 1 are proposed, involving intramolecular assistance by the cyclic ether oxygen.
Reduction of Co(II) with NaBH4 in the presence of triphenylphosphine
Authors: Holah D. G. , Hughes A. N. , Hui B. C. , Kan C. T.
Published: May 2006

The reactions of NaBH4 with Co(II) compounds in the presence of triphenylphosphine (P) have been studied in ethanol and benzene solutions. The conditions for the isolation of the Co(I) complexes, Co(BH4)Pn (n = 2, 3), have been established and the structures of these species are discussed in the light of various physical measurements.
Basicité des composés (R2N)3–n(RO)nP vis-à-vis de BH3. Etude comparée par résonance magnétique nucléaire et enthalpies de réaction
Authors: Elegant Lucien , Gal Jean-François , Jouany Claude , Jugie Gérard
Published: May 2006

The equimolecular adducts between aminoalkoxyphosphines (Me2N)3–n(tBuO)nP with n = 1,2, and 3) and borane BH3 have been prepared and characterised. The nmr study has been undertaken to compare some parameters (1JBH, 1JBP, δ11B etc.) with both those derived from the enthalpies of reaction of diborane with the parent phosphines and from the displacement reactions. No overall correlations between the 1JBP coupling constants and the complex stabilities seem evident.
The crystal and molecular structure of (4-diethylaminophenyl)diazenyltriphenylphosphonium tetrafluoroborate
Authors: Einstein Frederick W. B. , Sutton Derek , Vogel Peter L.
Published: May 2006

The title compound crystallizes in the space group P21/c with four formula units in a cell of dimensions a = 10.146(6) Å, b = 10.593(4) Å, c = 26.31(1) Å, β = 103.14(3)°. Using 1496 observed reflections (I = 2.3σ(I)) in the range 0° < 2θ < 40° measured on a Picker FACS-1 automatic diffractometer with Mo-Kα radiation, the structure was solved (symbolic addition) and refined (full-matrix least-squares procedure) to R = 0.062 (Rw = 0.058), with all hydrogen atoms included and all non-hydrogen atoms having anisotropic thermal parameters. The dimensions within the cation are consistent with a delocalized electronic structure which is intermediate between valence formulations involving benzenoid or quinonoid structures for the (4-diethylaminophenyl)diazenyl residue. Some important bond lengths are N3—C22 1.336(7) Å, N2—C19 1.356(7) Å, N1—N2 1.308(6) Å, and P—N1 1.648(5) Å.
Synthesis and 1H and 13C nuclear magnetic resonance spectra of some 4-alkylidene-1-pyrazolines and alkylidenecyclopropanes
Authors: Crawford Robert J. , Tokunaga Hirokazu , Schrijver Louis M. H. C. , Godard Jacky C. , Nakashima Thomas
Published: May 2006

The 1Hmr and 13Cmr spectra for 15 4-alkylidene-1-pyrazolines and 19 alkylidenecyclopropanes are reported. The assignments of E and Z isomers are made on the basis of shielding effects about the exo cyclic double bonds. The addition of diazomethane-d2 to 1,2-butadiene is shown to be both regiospecific and stereospecific.
The bromination of 3-arylpropynes: Evidence for phenyl participation at a vinyl cation
Authors: Pincock James A. , Somawardhana C.
Published: May 2006

The bromination of substituted 3-arylpropynes in acetic acid has been examined. The only products obtained are 1,2-dibromo-3-arylpropenes; the stereochemistry of the dibromides is predominantly trans except for the 4-methoxy isomer which gives 83% cis and 17% trans. In the presence of 0.1 M lithium bromide all substrates give predominantly trans products. Combined with rate studies, these results indicate that these acetylenes react by an unsaturated cyclic bromonium ion except for the 4-methoxy case where phenonium ion stabilization of a vinyl cation is implicated. In the presence of lithium bromide a bromide ion catalyzed addition of molecular bromine (AdE3) occurs.
The chemistry of N,N′-dimethylformamidine. I. Formation from potassium methylamide and its thermal stability
Authors: Halliday James D. , Symons E. Allan , Bonnett J. Douglas
Published: May 2006

The thermal decomposition of methylamine solutions of potassium methylamide (PMA) to form the potassium salt (PDMFA) of N,N′-dimethylformamidine (DMFA) has been studied as a function of PMA concentration at 60 °C. Although concentrated solutions yield normal pseudo-first-order plots (analysis by ultraviolet–visible spectrophotometry), dilute solutions (< 0.05 mol L−1 PMA) show an increase to a new rate after about 20 h reaction.The mechanism for this novel amidine salt synthesis is discussed in terms of rate-limiting β-hydride elimination from the PMA ion pair. The relatively sharp rate increase with time for the low concentration runs may arise from a slow build up of one or more intermediates. The resulting inverse dependence of kobs on PMA concentration is probably related to ion pair–dimer association phenomena.Pure DMFA has been produced by this reaction, and its thermal stability examined. DMFA decomposes above 100 °C to form bis-N-(N′-methylmethylenimine)methylamine and methylamine; the series of equilibria involved have been shown to be reversible.
The chemistry of N,N′-dimethylformamidine. III. Tautomerism and hindered rotation
Authors: Halliday James D. , Symons E. Allan , Bindner Patrick E.
Published: May 2006

Proton nmr and infrared studies of neat N,N′-dimethylformamidine (DMFA) have shown that the cis isomer 1 is present exclusively and that it undergoes tautomerism. At 25 °C, ktaut = 8.2 × 102 s−1, Ea = 41.5 ± 1.5 kJ mol−1, ΔH≠ = 39.1 ± 1.5 kJ mol−1, and ΔS≠ =−57.5 ± 5.0 J mol−1 K−1. The tautomerism is proposed to occur through a hydrogen-bonded cyclic dimer. The effects of solvent on the tautomeric rate in DMFA have also been investigated for CD3NH2 and CDCl3 solutions.Potassium N,N′-dimethylformamidide (PDMFA) in CD3NH2 does not exhibit hindered rotation about the single C—N bond on the nmr lime scale over the temperature range −56 to 25 °C. However, protonated DMFA undergoes hindered rotation about this bond in highly acidic media (97 wt.% H2SO4 at 25 °C, krot = 0.16 × 102 s−1, Ea = 35.4 ± 0.8 kJ mol−1). The acid catalysis is interpreted as occurring through formation of the diprotonated species. The two nitrogens in protonated DMFA have different base strengths.
Aminoglycoside antibiotics: Synthesis of pseudotrisaccharides derived from neamine and paromamine
Authors: Hanessian Stephen , Ogawa Tomoya , Takamoto Tetsuyoshi
Published: May 2006

Pseudotrisaccharides of paromamine having a 6-O-(β-D-ribofuranosyl) and 6-O-(α-D-arabinofuranosyl) moieties were prepared from appropriately N,O-substituted derivatives of paromamine by glycosylation reactions. Selective functionalization at C-6′ in 6-O-(β-D-ribofuranosyl)paromamine led to the corresponding neamine-containing pseudotrisaccharide. None of these semisynthetic aminoglycosides possessed antibacterial activity, although at least one of them has been shown to be a substrate for the phosphotransferases I and II. The unnatural attachment of a pentofuranosyl moiety at C-6 of the 2-deoxystreptamine unit in these pseudotrisaccharides is, therefore, detrimental to their antibacterial action, unlike amino sugar containing analogs at the same position.
The solid phase synthesis of monoester monoamides and monoester monoalcohols from symmetrical diacid chlorides
Authors: Goldwasser Judah M. , Leznoff Clifford C.
Published: May 2006

A 2% crosslinked divinylbenzene–styrene copolymer, incorporating benzyl alcohol groups, was used to monoprotect the symmetrical diacid chlorides, ClOC(CH2)nCOCl (where n = 2, 3, 4, and 8), terephthaloyl chloride and isophthaloyl chloride. Subsequent reaction of the resulting polymer-bound monoester monoacid chloride with aniline, benzylamine, dimethylamine, tert-butylamine, or ammonia yielded polymer-bound monoester monoamides, which on base cleavage and esterification gave monoester monoamides inhighyield. Borohydride reduction of polymer-bound sebacoyl chloride, terephthaloyl chloride, and isophthaloyl chloride gave their respective polymer-bound monoester monoalcohols, which on base cleavage from the polymer and esterification yielded the monoester monoalcohols in good yield along with some recovered dimethyl esters of the respective starting diacid chlorides.
Quelques aspects du spectre d'absorption infrarouge de complexes par liaison hydrogène
Authors: Bueno Willie A. , Mazzaro Neusa M.
Published: May 2006

A discussion is given of the infrared spectra in the region 4000 to 1600 cm−1 of 24 hydrogen-bonded complexes between aliphatic amine oxides and a number of phenol derivatives.
Interaction fluorure d'hydrogène–acide perchlorique: Reactivité du nitromethane dans le milieu
Authors: Belin Claude , Potier Jacqueline
Published: May 2006

Hydrogen fluoride reacts with perchloric acid yielding an incongruently melting compound (−117 °C); by ir spectroscopy, we demonstrate that HClO4 is linked to a (HF)n polymer through a weak hydrogen bond. The liquid of the same composition still contains a small amount of the complex; HF is really a base forHClO4. The reactivity of MeNO2 was studied in this liquid acidic medium and the nitromethane is found to be somewhat stronger than HF.
Synthesis of triquinacene and some of its derivatives
Authors: Deslongchamps Pierre , Cheriyan Ukken Ouseph , Lambert Yvon , Mercier Jean-Claude , Ruest Luc , Russo Robert , Soucy Pierre
Published: May 2006

Several routes for the synthesis of triquinacene (1) and 2,3-dihydrotriquinacen-2-one (3) are described using Thiele's acid as starting material.
Exciton and electron interaction in covalently-linked dimeric porphyrins
Authors: Paine III John B. , Dolphin David , Gouterman Martin
Published: May 2006

The interactions between dimeric porphyrins, covalently linked at their peripheries, have been measured from their electronic absorption spectra and 13C nmr spectra.
Assembly of the carbon skeletal framework of erythronolide A
Authors: Hanessian Stephen , Rancourt Georges , Guindon Yvan
Published: May 2006

The construction of the 15-carbon chiral framework of erythronolide A is described, based on a synthetic strategy that uses carbohydrate-derived 'chiral templates' as prefabricated segments of the target molecule.
The X-ray crystal structure of (±)-flavipucine
Authors: White Peter S. , Findlay John A. , John Tam Wah Hung
Published: May 2006

Synthetic (±)-flavipucine (C12H15O4N) is monoclinic, space groupP21/c, with a = 11.506(5), b = 8.765(5), c = 11.981(7) Å, β = 91.09(2)°, Z = 4. X-ray analysis confirms its structure as 1, 3′-isovaleryl-6-methyl pyridine-3-spiro-2′-oxiran-2(1H),4(3H)-dione and reveals the configuration of the oxirane to be Z.
Solvolysis rates in aqueous – organic mixed solvents. V. Kinetics of the alkaline decarboxylation of trichloroacetate ion in water – ethanol solutions
Authors: Diefallah El-Hussieny M. , El-Nadi A. M.
Published: May 2006

The kinetics of the alkaline decarboxylation of trichloroacetate ion in ethanol–water solutions have been studied over the temperature range 35.0 to 70.0 °C. The rate of reaction is first order with respect to the trichloroacetate ion and is independent of the concentration of the hydroxide ion. The reactivity is enhanced by increasing the concentration of ethanol in the water–ethanol solutions and the rate of reaction varies with ethanol addition in a nonlinear manner. The rate of reaction increases with the reciprocal of the dielectric constant of the medium and the plot of log k vs. 1/D is approximately linear for solvent mixtures with less than about 0.7 water mole fraction but is strongly curved towards the pure water end. The activation parameters for the reaction show a regular increase in the solvent composition range 0.3 to 1.0 water mole fraction. The results are discussed in terms of the influence of solvent internal pressure and polarity on reactivity and of the increased amount of hydrogen-bonded structure in the water-rich solutions.
Excess volumes of chloroform and bromoform mixtures with some n-alcohols at 303.15 K
Authors: Singh Prem P. , Sharma Buta R. , Sidhu Kuljits S.
Published: May 2006

Excess volumes of binary mixtures of chloroform and bromoform with the following n-alcohols: methanol, ethanol, and n-propanol have been measured as a function of composition at 303.15 K by a dilatometric method.
Approaches to the synthesis of triterpenes. V. An unusual acid-catalysed rearrangement of a β,γ-unsaturated ketone
Authors: ApSimon John W. , Badripersaud Satyanand , Post Michael L. , Gabe Eric J.
Published: May 2006

The reaction of 2-keto-1β,4aβ-dimethyl-1α-[2-(3-keto-1,4,4-trimethylcyclohexyl)ethyl]-7-methoxy-1,2,3,4,4a,9-hexahydrophenanthrene 1a and b with p-toluenesulphonic acid in boiling xylene yields the rearranged product, 1,10-dimethyl-2-[2-(3-keto-1,4,4-trimethylcyclohexyl)-ethyl]-7-methoxy-3,4-dihydroanthracene (3). Crystals of 3 are monoclinic, space group P21/c, Z = 4, with a = 7.2684(3), b = 30.942(2), c = 10.5544(7) Å, β = 98.24(1)°. The structure was determined by direct methods from diffractometer data and refined by block-diagonal least-squares to an R of 0.043 for 1810 observed reflections. The molecule exhibits no unusual geometric features, although positional disorder is apparent in the cyclohexanone moiety.A possible route for the formation of 3 from 1a and b is presented.
Distillation extractive. II. Etude de l'interaction entre carbures insaturés et solvants dipolaires
Authors: Wakselman Claude , Bouquet Michel
Published: May 2006

The nature of the interactions between unsaturated hydrocarbons and dipolar aprotic solvents, which occur in the extractive distillations, has been studied by 13C nmr, dielectric constant, and dipole moment measurements. The results of these different methods are in agreement with dipolar interactions.
The conformational preferences and the rotational barriers of some simple cyclopropylcarbinyl cations
Authors: Okazawa Nancy , Sorensen Ted S.
Published: May 2006

The ground-state rotamer conformations of a series of 'bisected' dicyclopropylcarbinyl cations, cyclopropylallyl cations, and phenylcyclopropylcarbinyl cations have been systematically investigated for the first time, employing 1H and 13C nmr spectroscopy. In the absence of significant steric factors, these cations adopt conformations involving the 'most extended conjugation.' However, this preference is not overwhelming because, in the presence of other substituents of only modest bulk, other less extended conformations exist. Cation systems, where two of these conformations are observable, have been found for each of the three major types described above. From an nmr line-broadening analysis, the populations of the two conformers and the energy barrier interconverting them have been obtained. In phenyldicyclopropylcarbinyl cations, at least one of the conformers involves a nonplanar phenyl ring.
Polarographic investigation of electron donor–acceptor complexes
Authors: Ramaley Louis , Gaul Sonia
Published: May 2006

Using a computer-controlled precision polarograph the formation constants of electron donor–acceptor (EDA) complexes formed from aromatic hydrocarbons and nitrofluorene derivatives have been determined in acetonitrile. The EDA interactions are of the same magnitude in this solvent as in less polar solvents. The strength of the complexes is related to the reduction potential (or electron affinity) of the acceptors and the size of the π system of the donors. Spectra of the complexes were computed from spectra of mixtures of accepter and donor with the help of the polarographic data. No relationship between the molar absorptivity of the charge-transfer band and the formation constant was apparent from these spectra.
Temperature dependence of adiabatic compressibilities of and sound velocities in p-dioxane–water mixtures
Authors: Murthy Neriyanuri Manohara , Subrahmanyam Saraswatula Venkata
Published: May 2006

The effect of p-dioxane on the temperature of adiabatic compressibility minimum (TACM) and sound velocity maximum (TSVM) in water have been studied. Both the structural shifts, [ΔTβ str]exp and [ΔTu str]exp, are found to be positive, increasing with concentration and reaching maximum values around [Formula: see text] These results have been explained as due to the formation of hydrates of dioxane of varying composition indicating the existence of long range order in the water + p-dioxane System in the water-rich region.
Mixed oxidation state compounds of antimony: a 121Sb Mössbauer study of some antimony–fluorine systems
Authors: Ballard Jack G. , Birchall Thomas , Gillespie Ronald J. , Maharajh Edward , Tyrer David , Vekris John E.
Published: May 2006

Antimony-121 Mössbauer spectra for [Sb2F42+][SbF6−]2 and three compounds containing the [Sb3F14−] ion are reported. The Mössbauer data are discussed in relation to their known structures. Two of the compounds give spectra which, on analysis, give η values of unity.
The chlorination of sulfides: A reassessment of product controlling factors
Authors: Ahern Terence Patrick , Kay Denis George , Langler Richard Francis
Published: May 2006

A reexamination of previous proposais for the prediction of regioselectivity in sulfide chlorinations has found them to be unsatisfactory. A new basis for such predictions is advanced viz. the electronegativity difference (ΔXp) of the substituents attached to the α- and α′-carbon atoms of the sulfide substrate. Upon establishing that the new basis for these predictions is satisfactory, it is successfully applied to the problem of predicting reactivity differences in isomeric sulfide chlorinations. The formation of isomeric sulfonium ions is used to establish the failure of possible isomerization processes to occur under normal reaction conditions.
Structural study of the cesium oxypentafluorouranate (VI) CsUOF5
Authors: Joubert Philippe , Weulersse Jean-Marc , Bougon Roland , Gaudreau Bernard
Published: May 2006

Powder samples of cesium oxypentafluorouranate(VI) were studied by both neutron diffraction and 19F broad Une nuclear magnetic resonance.CsUOF5 crystallises with the [Formula: see text] space group, with the parameters a = 5.41 ± 0.01 Ǻ; α = 95°34′ ± 5′. The structure, which was found to be unchanged at temperatures as low as 4.2 K, was interpreted by a statistical occupation of six-fold equivalents sites, the occupation rate being 1/6 and 5/6 for oxygen and fluorine, respectively. The nmr study showed that the disorder corresponding to this structure was of dynamic type, and that the UOF5− ions were in isotropical rotation. The motion is observable at temperatures as low as 223 K with a characteristic time τ equal to3 × 10-5 s at 266 K. On the other hand, it was also shown through this nmr study that the point symmetry of the UOF5− ion corresponds to the C4v group, with the axial fluorine being more covalent than the equatorial ones. Consistency of the diffraction and nmr results is discussed.
The reactions of lithioacetonitrile and lithiomethoxyacetonitrile with certain ketones
Authors: Beam Charles F. , Shealy Keith D. , Risinger Sharon A. , Brown Jane , Sides Kimberly L. , Hanberry Candace R. , Pavlakovich Kathy P. , Davis Steven E.
Published: May 2006

Lithioacetonitrile and lithiomethoxyacetonitrile were condensed with ketones to give either mono- or dialdol condensation products.