bluuebunny/crossref_metadata_2025 huggingface dataset:
Biphasic photochemistry: micelle solutions as media for photochemical cycloadditions of enones
Authors: Berenjian Nader , Mayo Paul De , Sturgeon Mary-Ellen , Sydnes Leiv K. , Weedon Alan C.
Published: May 2006

The possible application in synthesis of a micellar solution as a medium in the photocycloaddition of enones to alkenes has been examined. It is found that the micelles are useful in increasing the effective concentration of reactants, have some ability in directing reaction regiochemistry, and may reduce hydrogen atom transfer in intermediate biradicals.
La liaison phosphazène dans quelques nouveaux iminophospholanes. Diversité de comportement réactionnel
Authors: Marre Marie Rose , Sanchez Michel , Brazier Jean François , Wolf Robert , Bellan Jacques
Published: May 2006

Using the Staudinger reaction, we have synthesized twelve iminophospholanes (1–12) with dioxa (1–4), oxaza (5, 6), and diaza (7–12) ring systems. We have never observed any phosphazene bond dimerization with diazaphospholane compounds, whatever the nature of the group on the imino atom. For the tetramethyl dioxaphospholane compounds (1, 2, 4), the thermal rearrangement[Formula: see text]occurs with the intracyclic oxygen atom. Last of all, the reactivity of the phosphazene bond with methanol differs according to the nature of the ring: addition leading to the pentacoordinated species in pinacolic compounds, intermolecular associations (hydrogen bonding) in diazaphospholane derivatives.
Effective interactions for the configurations 3d34p + 3d24s4p + 3d4s24p in the first spectrum of titanium
Authors: Roth C.
Published: May 2006

Energy levels and Lande g-factors for the configurations 3d34p + 3d24s4p + 3d4s24p in the first spectra of titanium were calculated and compared with experimental values. The calculations were done in intermediate coupling taking into account explicitly the interactions between configurations, as well as complete effective interactions of the core, and effective interactions d–p.Due to the insertion of the various effective interactions and a successful starting point based on a general treatment of the odd configurations in the first spectra of the iron group, there was excellent agreement between the experimental and calculated levels.On fitting 164 levels using 28 free interaction parameters a mean error of only 117 cm−1 was obtained, i.e., about 0.3% average difference between the experimental and calculated levels. The experimental and calculated g-factors corresponded very closely.
Crystalline structure and vibrational spectra of cis-dichlorodiammine-trans-dihydroxo- platinum(IV), PtCl2(NH3)2(OH)2
Authors: Faggiani R. , Howard-Lock H. E. , Lock C. J. L. , Lippert B. , Rosenberg B.
Published: May 2006

The structure of cis-dichlorodiammine-trans-dihydroxoplatinum(IV), PtCl2(OH)2(NH3)2, has been determined by X-ray diffraction. The tetragonal space group, P42/n has cell dimensions a = 7.328(4), c = 11.362(5) Å and has four formula units in the cell. Intensities were measured using MoKα radiation and a Syntex P21 diffractometer. The crystal structure was determined by standard methods and refined to R1 = 0.0460, R2 = 0.0639 based on 447 independent reflections. The platinum atom has roughly octahedral coordination and Pt—Cl, Pt—N, Pt—O distances (2.306(4), 2.00(1), 2.00(1) Å) are normal. The crystal is held together by hydrogen bonds, and the vibrational spectra have been correlated with observed features of the hydrogen bonding.
Nucleic acid related compounds. 37. Convenient and high-yield syntheses of N-[(2-hydroxyethoxy)methyl] heterocycles as "acyclic nucleoside" analogues
Authors: Robins Morris J. , Hatfield Peter W.
Published: May 2006

Treatment of 1,3-dioxolane with acetyl bromide gave (2-acetoxyethoxy)methyl bromide (2a) in 88% yield. A number of pyrimidines and three chloropurines were trimethylsilylated and coupled with 2a. The respective N-1 and N-9 alkylated products (obtained in 79–89% yields) were deacetylated to give N-[(2-hydroxyethoxy)methyl] heterocycles. The 6-amino or 6-chloro substituent of the 2-amino-6-substituted-purine derivatives was hydrolyzed smoothly with adenosine deaminase to give 9-[(2-hydroxyethoxy)methyl]guanine (acycloguanosine), the potent antiviral agent.
Nucleic acid related compounds. 38. Smooth and high-yield iodination and chlorination at C-5 of uracil bases and p-toluyl-protected nucleosides
Authors: Robins Morris J. , Barr Philip J. , Giziewicz Jerzy
Published: May 2006

Treatment of uracil bases and protected nucleosides with iodine monochloride (ICl) gave the corresponding 5-iodouracil products in over 95% purified yields. Analogously facile chlorination was effected with iodobenzene dichloride (PhICl2). Protection of the nucleosides as p-toluyl esters provided reactants that were soluble in organic solvents and crystallized readily in high yields.
Addition photochimique de nitrènes sur les éthers vinyliques et sucres insaturés
Authors: Kozlowska-Gramsz Elzbieta , Descotes Gérard
Published: May 2006

The photochemical addition of nitrenes to cyclic vinylic ethers and unsaturated sugars, in the presence of alcohols, gave the products of alcoholysis of the aziridine intermediates. The reactivity and stereoselectivity of this addition is discussed. The application of this reaction to the synthesis of aminosugars is described.
Carbon-13 nuclear magnetic resonance studies of organotellurium compounds. II. Chemical shift trends
Authors: Chadha Raj. K. , Miller Jack M.
Published: May 2006

13C nmr chemical shifts are reported for some aromatic and aliphatic tellurium compounds. For a given organic group, the shift of the C1 atom varies in the order [Formula: see text], as expected from electronegative considerations. The C2 atom experiences an opposite trend while the C3 and C4 atoms of the ring experience smaller changes. The chemical shifts of para-substituted aromatic tellurium compounds do not show additivity of contributions from the substituents.
The Schmidt reaction of anthraquinones
Authors: Flemming Cecily A. , Gandhi Sham S. , Gibson Martin S. , Ruediger Edward H.
Published: May 2006

Schmidt reaction (sodium azide/sulfuric acid) of 1,5- and of 1,8-dichloroanthraquinones gives, in each case, both of the theoretically possible lactams (2,3,5,6-dibenzoazepin-4,7-diones). Two of the four theoretically possible lactams have been identified from Schmidt reaction of 1- and 2-chloroanthraquinones respectively. Methods used include: (a) preferential hydrolysis of one lactam and identification of the isomeric aminoanthraquinone formed on cyclodehydration of the resulting amino acid; (b) identification of the isomeric aminoanthraquinone(s) formed on direct treatment of a lactam (or mixture of lactams) by sulfuric acid; (c) cleavage by potassium tert-butoxide of the amino acid formed by preferential hydrolysis of one lactam and identification of the resulting benzoic acid as its methyl ester.
Structure of the Cornubert ketone
Authors: Pettit George R. , Thomas Evan G.
Published: May 2006

The self-condensation of cyclohexanone in diethyl ether catalyzed by sodium amide has been found to provide a one-step route to pyran 3. Evidence is presented that the Cornubert ketone formed by this reaction corresponds to ketol 2 which readily rearranges under dehydrating conditions to afford pyran 3. Structural elucidation of pyran 3 was achieved by a combination of degradative (3 → 5b), synthetic (8 → 5b), and spectral methods. Xanthene 7, a key dehydrogenation product of ketol 2, was converted by selective reduction to dihydropyran 5b. The five-step synthesis of dihydroxypyran 5b from 1-carbomethoxycyclopentanol (8) provided unequivocal evidence for the structure assigned pyran 3 and xanthene 7.
The biosynthesis of retronecine
Authors: Grue-Sørensen Gunnar , Spenser Ian D.
Published: May 2006

An experiment with putrescine, doubly labelled intramolecularly, with 15N and 13C at the adjacent C-atom, demonstrates that a C4–N–C4 compound with C2v symmetry serves as a precursor of retronecine, the most common base of the Senecio alkaloids. The C4–N–C4 compound is, in turn, generated from two ornithine-derived precursor units. This was demonstrated by a degradation sequence whereby the distribution of label from [5-14C]-, [5-3H]-, and [4-3H]ornithine within retronecine was fully accounted for.
Total synthesis of racemic 2-desoxystemodinone and stemodinol; the identity of natural "stemodinol" with stemarin
Authors: Kelly Ronald B. , Harley Mary Lou , Alward Sandra J. , Manchand Percy S.
Published: May 2006

Total syntheses of the naturally occurring diterpenoid 2-desoxystemodinone (3) and the diterpenoid structure 2 ("stemodinol") are described. The synthetic diterpenoid 2 was not identical to an authentic sample of "stemodinol". The authentic sample was found to be stemarin to which structure 2 had been erroneously assigned in the literature. It would appear that the diterpenoid represented by 2 has not been isolated from natural sources.
Synthesis of 4,5-disubstituted imidazoles
Authors: Kavadias Gerry , Luh Bing , Saintonge Roger
Published: May 2006

Introduction of a triphenylmethyl group on the nitrogen of imidazole-4,5-dicarboxylic acid esters or 4,5-dihydroxymethylimidazole resulted in deactivation of the functional group adjacent to the protecting group and allowed reactions to take place preferably or exclusively on the other functional group. Thus, dimethyl 1-triphenylmethylimidazole-4,5-dicarboxylate (2), on treatment with hydrazine and methylamine produced methyl 4-hydrazinocarbonyl-1-triphenylmethylimidazole-5-carboxylate (3a) and methyl 4-methylaminocarbonyl-1-triphenylmethylimidazole-5-carboxylate (3b), respectively. Reduction of 2 with lithium borohydride gave methyl 4-hydroxymethyl-1-triphenylmethylimidazole-5-carboxylate (4a). Treatment of 4,5-dihydroxymethyl-1-triphenylmethylimidazole (5a), with trimethylacetyl chloride and with acetic anhydride afforded 5-hydroxymethyl-4-trimethylacetoxymethyl-1-triphenylmethylimidazole (6a), and 4-acetoxymethyl-5-hydroxymethyl-1-triphenylmethylimidazole (6c), respectively. Oxidation of 5a with activated manganese dioxide produced the monoaldehydes 9 and 10 in a ratio of 11:1. A new mild process for deprotection of N-triphenylmethylimidazoles, compatible with acid sensitive groups in the molecule, is reported. The synthesis of several 4,5-disubstituted imidazoles is also described.
The soivolysis of trans-1,2-diphenyl-2-phenylthio[1-13C]vinyl tosylate in anhydrous or aqueous acetic acid
Authors: Lee Choi Chuck , Fiakpui Charles Y. , Quail J. Wilson
Published: May 2006

The acetolysis of trans-1,2-diphenyl-2-phenylthiol[1-13C]vinyl tosylate (2-OTs-1-13C) under anhydrous conditions (HOAc–Ac2O–NaOAc) gave trans-1,2-diphenyl-2-phenylthio[1,2-13C]vinyl acetate (2-OAc-1,2-13C) as product. The label was scrambled equally over C-1 and C-2 and there was no detectable amount of cis-product. These results are consistent with the involvement of an intermediate sulfur-bridged thiirenium ion in the reaction. Soivolysis of 2-OTs-1-13C in 70% HOAc – 30% H2O containing 3 equiv. of NaOAc gave 1,2-diphenyl-2-phenylthio[1,2-13C]ethanone (α-phenyl-α-(phenylthio)acetophenone) (5-1,2-13C) and 1,2-diphenyl[1,2-13C]ethanone (desoxybenzoin) (6-1,2-13C) as major and minor products, respectively. The 13C-label in both of these ketones was again equally distributed over C-1 and C-2. Further studies with unlabeled 2-OTs showed that its soivolysis in aqueous HOAc gave, besides ketones 5 and 6, some benzil and diphenyl disulfide. It was also found that 6, benzil, and diphenyl disulfide were derived from the initial product 5. A possible mechanism for these conversions is proposed.
Large hydrophobic interactions with clearly defined geometry. A dimeric steroid with catalytic properties
Authors: Guthrie J. Peter , Cullimore Patricia A. , McDonald Robert S. , O'Leary Stella
Published: May 2006

The steroid dimer α,α′-bis(17β-(4'-imidazolyl)-11-keto-5α- androstan-3β-amino)-p-xylene, 3, has been synthesized by reductive animation of 17β-(4′-imidazolyl)-5α- androstane-3,11-dione by p-xylenediamine in the presence of sodium cyanoborohydride, and by reductive amination of terephthalaidehyde by 3β-amino-17β-(4′-imidazolyl)-5α- androstan-11-one. The second method is stereochemically unambiguous; the first is not. Compound 3 acts as a catalyst for the hydrolysis of 3-arylpropionate esters of 3-hydroxy-4-nitrobenzoic acid. For the phenanthryl propionate the rate enhancement relative to imidazole is 200-fold, and the rate enhancement relative to the hypothetical rate for the propionate reacting with the steroid by the same transition state geometry is 3000-fold. The slope of a plot of log kcorr vs. π for the reaction of 3b with aryl propionate esters was 0.83; the corresponding slope for 12 was 0.39. This provides a design parameter for the construction of artificial enzymes.
Flow 1H nmr study of the rapid nucleophilic addition of amino acids to 4-formylpyridine
Authors: Tan Liang K. , Cocivera Michael
Published: May 2006

Rapid addition of primary amino acids and imidazole to 4-formylpyridine to form carbinolamine intermediates in water has been studied by means of stopped-flow 1H nuclear magnetic resonance spectroscopy. The equilibrium constant Kn for this process was determined using stopped-flow uv spectroscopy. For the amino acid D,L-alanine and its derivatives, D,L-alanine methyl ester and D,L-alanylglycine, Kn does not appear to correlate with Ka, the acid dissociation constant. Values of kn, the addition rate constant, appear to be independent of pH and buffer concentration for these nucleophiles. The limited data indicate that the variation in rates of nucleophilic addition to 4-formylpyridine cannot be accounted for in terms of pKa, Kn or related to systematic changes in structure of the nucleophile. As a group, the primary amino acid D,L-alanine and its derivatives have comparable kn values within a factor of two in spite of their different pKa values. Imidazole, an aromatic secondary diamine, has a kn value that is 10 to 20 times larger than these primary amines and has a relatively small Kn value. At the same time, its kn value is comparable to that found previously for sarcosine, a secondary acyclic amino acid having substantially larger pKa and Kn values. The nucleophilic addition step of the primary amino acid and derivatives is rapid relative to the subsequent dehydration and prototropic shift steps. It occurs in a pH range at which pyridine nitrogen protonation is negligible.
Amino acid addition to 4-formylpyridine and its quaternized salt: transamination
Authors: Tan Liang K. , Cocivera Michael
Published: May 2006

Flow and stopped-flow 1H nuclear magnetic resonance spectroscopy of aqueous solutions have been used to study the reaction between 4-formylpyridine or 4-formyl-1-methylpyridinium iodide and D,L-alanine as well as its methyl ester and D,L-alanylglycine. Because resolved signals can be observed for the alanyl-CH3-proton resonance of the amine, the aldimine, and the ketimine, the time dependence of each species was followed, and the sequence of steps leading to transamination could be studied. As was found previously with alanine, the conversion of aldimine to ketimine appears to be too slow to be detected when 4-formylpyridine is reacted with alanine (pH range to 10) or alanyl methyl ester (pH range 7 to 8). For these systems reaction proceeds until an equilibrium between aldimine and reactants is established. Because the equilibrium constant for the addition step is measured separately, the constant for the equilibrium Kd between carbinolamine and aldimine could be determined. The rate constants for the forward and reverse steps of this equilibrium are independent of buffer but depend on pH. For alanylglycine between pH 7.2 and 7.7, the same process was found to occur. However between pH 8.2 and 10.1, the aldimine derived from this amine undergoes a prototropic shift to form the corresponding ketimine with a rate constant that depends on the concentration of DABCO at each pH. Thus, the change from α-carboxylate anion of alanine (or other amino acids studied previously) to the uncharged α-amide of alanylglycine causes a distinct increase in the rate of prototropic shift when 4-formylpyridine is the electrophile. For the more reactive 4-formyl-1-methylpyridinium iodide, aldimine to ketimine conversion was found to occur for alanine and alanylglycine. During reaction of the latter, a broad nmr signal occurs. This signal may be due to the dihydropyridine structure suggested for an intermediate detected spectrophotometrically for the reaction involving alanine or glycine.
Diamagnetic metal ion – nucleoside interactions in solution as studied by 15N nuclear magnetic resonance
Authors: Buchanan G. W. , Stothers J. B.
Published: May 2006

15N nuclear magnetic resonance chemical shifts are shown to be highly sensitive to site-selective diamagnetic metal ion binding for the nucleosides adenosine, cytidine, and guanosine. Conclusions regarding preferred complexation sites are compared with results derived from other physical measurements, and with expectations based on electron density calculations.
The Lewis acid complexes of α,β-unsaturated carbonyl and nitrile compounds. A nuclear magnetic resonance study
Authors: Childs Ronald F. , Mulholland D. Lindsay , Nixon Alan
Published: May 2006

1:1 Complexes of a range of Lewis acids with crotonaldehyde (1) have been systematically investigated by 1H and 13C nmr spectroscopy. Lewis acids employed were: BF3, BCl3, BBr3, SnCl4, TiCl4, SbCl5, AlCl3, EtAlCl2, Et2AlCl, Et3Al2Cl3, and Et3Al. Chemical shift changes in 1H nuclei remote from the Lewis acid group were found to be remarkably regular and consistent. The study has been extended to tiglaldehyde (2), pent-3-en-2-one (3), cyclohexenone (4), methyl crotonate (5), and crotonitrile (6) and the relationships between the chemical shift differences associated with complexation of these have been explored.
Lewis acid addticts of α,β-unsaturated carbonyl and nitrile compounds. A calorimetric study
Authors: Childs Ronald F. , Mulholland D. Lindsay , Nixon Alan
Published: May 2006

Enthalpies of complexation of the α,β-unsaturated Lewis bases crotonaldehyde, 1; methyl crotonate, 2; mesityl oxide, 3; and crotononitrile, 4; with each of the Lewis acids SnCl4, TiCl4, SbCl5, and BCl3 were measured in solution in CH2Cl2. The results indicate that while a qualitative agreement exists in the ranking of Lewis acids for each of the Lewis bases, there is only a modest quantitative correlation. Similarly, when compared with an nmr-derived Lewis acid scale, the enthalpies were found to agree with the qualitative ranking of Lewis acids, but exhibited only a poor correlation.
Metal complexes as antioxidants. 7. A kinetic and product study of the reaction of tertiary alkylperoxy radicals with cobalt(II) acetylacetonate.
Authors: Howard J. A. , Tong S. B.
Published: May 2006

not available
Absolute rate constants for hydrocarbon autoxidation. 30. On the self-reaction of the α-cumylperoxy radical in solution
Authors: Howard J. A. , Bennett J. B. , Brunton G.
Published: May 2006

not available
Réactivité carbanionique de l'enchainement Pv—CH2—CH2—S—. Application à la synthèse d'un nouveau type de coordinats phosphorylés tétradentés
Authors: Savignac Monique , Cadiot Paul , Mathey François
Published: May 2006

The tert-butyllithium metallation of compounds containing the group Pv—CH2—CH2—SR proceeds by elimination of the group SR (R = H, CH3) followed by addition of tert-BuLi. Application of this addition–elimination reaction to functionalized phosphine-oxides [Formula: see text] leads to the synthesis of γ-diphosphorylated compounds. These dissociate in basic medium following a mechanism which is the reverse of their formation as shown by treatment of the reaction mixture with p-chlorobenzaldehyde to give ethyl p-chlorocinnamate.

[Journal Translation]
Kinetics of the oxidation of diphenyl sulfide with hydrogen peroxide catalyzed by sodium metavanadate
Authors: Ogata Yoshiro , Tanaka Kazushige
Published: May 2006

The oxidation of diphenyl sulfide (Ph2S) by hydrogen peroxide in the presence of a catalytic amount of sodium metavanadate (NaVO3) has been studied kinetically by means of iodometry of hydrogen peroxide. The reaction rate is expressed as: v = k[NaVO3]st[Ph2S]2, when the concentration of catalyst is very low and [Ph2S]0/[H2O2]0 > 2, where []st and []0 mean stoichiometric and initial concentration, respectively. The effective oxidant may consist of polymeric as well as monomeric peroxyvanadate in view of the effect of concentration of catalyst on the rate. The main oxidizing species at low concentration of catalyst seems to be diperoxyvanadate VO5−. The rate constant k2 in v = k2[Ph2S]2 tends to decrease with initial concentration of H2O2, which is present in excess of the catalyst. A probable mechanism for the oxidation is discussed.
Complexes moléculaires d'hétérocycles soufrés et oxygénés. Étude spectrophotométrique de bandes de transfert de charge multiples
Authors: Canselier Jean-Paul , Domenech Serge , Stankovsky Štefan , Gautier Sabine
Published: May 2006

As with benzenoid donors, the electronic absorption spectra of the molecular complexes of simple or condensed sulfur or oxygen-containing five-membered heterocycles with TCNE (or DDQ) often show two charge-transfer bands. In many cases, the knowledge of the actual frequencies requires a technique of resolution. The results so obtained are correlated with the ionization potentials of donors on the one hand, and the refractivity of nonpolar solvents on the other hand.
Synthesis of (±)-lineatin by the photochemical cycloaddition of allene to anhydromevalonolactone
Authors: McKay William R. , Ounsworth Jim , Sum Phaik-Eng , Weiler Larry
Published: May 2006

(±)-Lineatin (1), the aggregation pheromone of an ambrosia beetle, was synthesized in five steps from anhydromevalonolactone (5) in 10% overall yield. The key step in the synthesis was a photochemical cycloaddition of 5 and allene. This photolysis produced two regioisomers (ca. 3:2) and efforts to improve the regioselectivity by varying the photolysis conditions or substituents on the allene were unsuccessful.[Formula: see text]
Développement d'un détecteur à plasma micro-onde pour chromatographie en phase gazeuse
Authors: Chevrier Gilles , Hanai Toshihiko , Tran Khanh-Chi , Hubert Joseph
Published: May 2006

The development of an atomic emission detector for gas chromatography is described. An atmospheric pressure microwave helium plasma generated with an original device called Surfatron was used as an atomization and excitation source. The characteristics of operation are defined and the analytical performances for carbon, chlorine, bromine, and iodine analyses are measured. Detection limits are in the order of pg/s and the dynamic range of the detector covers three orders of magnitude.
Nuclear analogs of β-lactam antibiotics. XV. Synthesis of 6-substituted 2-methylpenem-3-carboxylic acids
Authors: Ueda Yasutsugu , Martel Alain , Daris Jean-Paul , Belleau Bernard , Ménard Marcel
Published: May 2006

The synthesis of 6-substituted 2-methylpenem-3-carboxylic acids is described. The dianion 6 was prepared insitu from 2-methylpenem-3-carboxylic acid (5) by the addition of two equivalents of n-butyllithium in THF at −78 °C. This dianion reacted with deuterated acetic acid, acetone, acetaldehyde, benzaldehyde, and methyl thiomethylsulfonate to give 6-deuterio-, 6-(2′-hydroxy-2′-propyl)-, 6-(1′-hydroxyethyl)-, 6-(1′-hydroxybenzyl)-, 6-methylthio-2-methylpenem-3-carboxylic acids and their sodium or potassium salts, 7–11, respectively. The stereochemistry of the products is also discussed.
A comparison of the relative binding energies of H+ and NO+ to aromatic and haloaromatic bases by high pressure mass spectrometry
Authors: Stone John A. , Splinter Dena E. , Kong Soon Yau
Published: May 2006

Proton transfer equilibria [Formula: see text] and NO+ transfer equilibria [Formula: see text] have been studied for the following bases B, benzene, toluene, o-, m-, and p-xylene. NO+ transfer equilibria for fluoro- and chlorobenzene have also been studied. Pulsed electron beam, high-pressure ion source mass spectrometry has been used to obtain the equilibrium constant K and hence the free energy changes ΔG0 and from van't Hoff plots, ΔH0 and ΔS0. Entropy changes are in general much smaller for NO+ transfer than for H+ transfer but the magnitude of the changes in the proton affinity and NO+ affinity of toluene caused by a fluorine substituent is about the same, even though the absolute value of the proton affinity is greater by a factor of 4. The position of the F substituent on toluene has a marked effect on proton affinity but no effect on NO+ affinity. The latter appears to be responsive only to the inductive effect.
A reactive lactonic dienophile – 3-carbethoxy-5,5-dimethyl-2(5H)-furanone. Application to the synthesis of a monoterpenoid lactone
Authors: Liu Hsing-Jang , Browne Eric N. C. , Pednekar Purushottam R.
Published: May 2006

In contrast to the low dienophilicity generally observed for α,β-unsaturated lactones, the title compound 2 is shown to be a reactive dienophile. Under stannic chloride catalysis, it undergoes Diels–Alder reaction region- and stereoselectively with a variety of dienes at room temperature. The synthesis of (±)-o-mentha-1,3-dien-1→8-olide (20) has been achieved by a two-step sequence using lactone ester 2. Addition of 2 to 1-acetoxy-1,3-butadiene afforded epimeric acetoxy lactones 12 and 13 which were converted to the monoterpenoid lactone 20 by treatment with lithium iodide dihydrate in collidine.
Nuclear analogs of β-lactam antibiotics. XIV. Synthesis of penems via (4-tritylthio-2-azetidinon-1-yl)triphenylphosphoranylideneacetates
Authors: Martel Alain , Dextraze Pierre , Daris Jean-Paul , Saintonge Roger , Lapointe Philippe , Conway Terry T. , Monkovic Ivo , Kavadias Gerry , Ueda Yasutsugu , Elie Patrick , Patil Sham , Caron Gilles , Douglas James L. , Menard Marcel , Belleau Bernard
Published: May 2006

The preparation of (4-tritylthio-2-azetidinon-l-yl)triphenylphosphoranylideneacetates from 4-acetoxyazetidin-2-one is described. They are easily converted to mercuric or silver mercaptides. These mercaptides are acylated with a wide variety of acylating agents and cyclized to 2-substituted penem-3-carboxylates.
Calcul des déplacements chimiques par la méthode des perturbations finies au niveau INDO avec GIAO et approximation de London. I. 13C et 1H
Authors: Vauthier E. , Odiot S. , Tonnard F.
Published: May 2006

A formalism for the calculation of σ in the finite perturbation method is developed by keeping hermitian the first order perturbed matrix in B. The σ formalism is separated into mono, di, and triatomic terms, and the importance of the electron densities of neighboring and remote bonds is shown. 13C chemical shifts depend only slightly on the remote bonds in contrast to those for 1H. A calculation of the screening constant for a series of 16 sp and sp2 carbons gives an average precision of 5 ppm for the 13C nuclei.

[Journal Translation]
Introduction of 9-fluorenylmethyloxycarbonyl, trichloroethoxycarbonyl, and benzyloxycarbonyl amine protecting groups into O-unprotected hydroxyamino acids using succinimidyl carbonates
Authors: Paquet Alenka
Published: May 2006

9-Fluorenylmethyl succinimidyl, pentachlorophenyl, and benzotriazole-1-yl carbonates were prepared and their reactivity with L-serine and L-serine benzyl ester was compared. The most efficient reagent, 9-fluorenylmethyl succinimidyl carbonate, was used for the preparation of 9-fluorenylmethyloxycarbonyl derivatives of other hydroxyamino acids and hydroxyamino acid esters in high yields. The use of trichloroethyl and benzyl succinimidyl carbonates for an efficient conversion of hydroxyamino acids and their esters into the corresponding N-trichloroethoxycarbonyl and benzyloxycarbonyl derivatives is described.
13C nuclear magnetic resonance and Raman investigations of aqueous carbon dioxide systems
Authors: Abbott Theresa M. , Buchanan Gerald W. , Kruus Peeter , Lee Keith C.
Published: May 2006

13C-nmr spectra of carbon dioxide in water are reported for a wide range in pH. Chemical shifts were determined for the following species: CO2(g), CO2(aq), HCO3−(aq), CO32−(aq). A linear relationship was found between the shift of the 13C line and the fraction of carbonate ion calculated to be present, as well as between the ratio of the area under the 1067 cm−1 (carbonate) Raman peak to the sum of the area under the 1067 cm−1 and 1017 cm−1 (bicarbonate) peaks and the fraction carbonate.
Enzymes in organic synthesis. 23. Effects of organic solvents on horse liver alcohol dehydrogenase-catalyzed oxidation
Authors: Jones J. Bryan , Schwartz Harold M.
Published: May 2006

The effects have been evaluated of up to 50% (v/v) of methanol, tert-butyl alcohol, dimethylsulfoxide, sulfolane, acetonitrile, dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, acetone, 2-butanone, tetrahydrofuran, dimethoxyethane, diglyme, and dioxane on horse liver alcohol dehydrogenase (HLADH)-catalyzed oxidation of the representative alcohol substrate cyclohexanol. With the exception of dimethylsulfoxide and dimethylformamide, all solvents tested are suitable for use as cosolvents with HLADH in the oxidative and reductive directions.
Magnetic and spectroscopic studies of structure and bonding in hexafluorophosphate and hexafluoroarsenate complexes of copper(II)
Authors: Morrison Raymond M. , Thompson Robert C.
Published: May 2006

Complexes of composition CuL4(EF6)2 (where L is pyridine, 3-methylpyridine, or 4-methylpyridine and E is P or As) have been prepared and characterized by epr, electronic and infrared spectroscopic, and magnetic susceptibility studies. Results are consistent with elongated tetragonal–octahedral structures with coordinated anions. The coordinating strength of PF6− is estimated to be less than that of AsF6− and both are considered weaker than perchlorate. Analysis of the epr data indicates significant metal to heterocyclic ligand π-electron delocalization, the extent and nature of which depends on the orientation of the heterocyclic ring in the CuL4 chromophore. Analysis of infrared data suggests that the intensities of the v1 and v2 vibrations as they occur in EF6− complexes generally provide an indication of the strength of metal–anion interactions.
Rearrangement of 10-acetoxy-10-vinylcamphene
Authors: Lamb Nancy , Money Thomas , Rettig Steven J. , Trotter James
Published: May 2006

Treatment of 10-acetoxy-10-vinylcamphene with BF3 or HClO4 results in rearrangement to a bicyclo[3.2.1]octane derivative in preference to 5-endo-trigonal cyclization. Alkaline hydrolysis of this bicyclooctane yields a diol, crystals of which are orthorhombic, a = 9.571(1), b = 12.416(1), c = 18.860(2) Å, Z = 8, space group C2221. The structure was solved by direct methods and was refined by a full-matrix least-squares procedure to R = 0.035 and Rw = 0.044 for 930 reflections with I ≥ 3σ(I). The structure analysis has unambiguously identified the diol as 2,3-dimethyl-4-vinylbicyclo[3.2.1]octan-2,3-diol.
Orientation of the methoxyl group in cis- and trans-2-methoxy-4-methyl-1,3-dioxanes and related compounds as inferred by 1H and 13C nmr spectroscopy. The significance of the "exo-anomeric" effect
Authors: Rao Vanga S.
Published: May 2006

Carbon-13 chemical shifts and 13C—1H couplings are reported for some substituted 2-methoxy-1,3-dioxanes and related tetrahydropyran derivatives. These data, together with nuclear Overhauser enhancement experiments, provided evidence for a favored orientation of the methoxyl group. From an analysis of the 13C chemical shifts and the magnitude of vicinal 13C—1H coupling between —OCH3 and H-2, a possible dynamic-equilibrium orientation for the methoxyl group is proposed, and an evaluation of the significance of a "generalized exo-anomeric effect" is presented.
Anionic decomposition of an organic peroxide leading to o-xylene
Authors: Shahidi Fereidoon , Tidwell Thomas T.
Published: May 2006

Reaction of 1,2-dimethyl-1,2-dihydrophthalic anhydride (8) with t-BuOONa at 40 °C gave o-xylene as the only observed product. This reaction is proposed to occur through intermediacy of the anionic peroxide 10 whose conversion to o-xylene is calculated to be exothermic by 84 kcal/mol. Extension of this reaction to systems that do not have the possibility for gaining aromatic stabilization was unsuccessful.
Ring opening reactions of N-substituted-5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxamides
Authors: Kulka Marshall , Harrison W. A.
Published: May 2006

The amides prepared from 5,6-dihydro-2-methyl-1,4-oxathiin-3-carbonyl chloride 2 and imidamides 4, carbamimidothioates 4, 2-benzimidazolamine 7, 2-benzothiazolamine 12, and 2-thiazolamine have been studied. The reaction of 2 with imidamides 4 and with carbamimidothioates 4 in the presence of base gave the amides 5, which when heated in toluene underwent the 1,4-oxathiin ring opening and rearrangement to produce 2-substituted-5-[(2-hydroxyethyl)thio]-6-methyl-4(1H)-pyrimidinones 6. Acylation of 2-benzimidazolamine 7 with 2 yielded the amide 10. This, in boiling ethanol, ring opened and rearranged to give the compound 11. The reaction of 2-benzothiazolamine 12 with 2 gave the rearrangement product 14 directly and neither of the possible amides 13 and 15 could be detected. The amide 15 was synthesized by an unambiguous route from 2-aminobenzenethiol and 5,6-dihydro-2-methyl-1,4-oxathiin-3-carbonyl isothiocyanate 3. It would not undergo ring opening and rearrangement when heated. Acylation of 2-thiazolamine with 2 yielded a mixture from which the amide 19 and the rearrangement ester 18 were separated. Structural assignments are based mainly on nmr, uv, and ir spectral evidence.
New catalysts and procedures for the dimethoxytritylation and selective silylation of ribonucleosides
Authors: Hakimelahi Gholam H. , Proba Zbigniew A. , Ogilvie Kelvin K.
Published: May 2006

Procedures have been developed for the selective formation of (a) 2′,5′-silylated ribonucleosides and (b) 3′,5′-silylated ribonucleosides. These procedures also permit the selective silylation at either the 2′- or 3′-position of dimethoxytritylated ribonucleosides. The procedures involve nitrate or perchlorate ion catalysis for selective reaction at 2′-positions and a combination of silver ion and DABCO or 4-nitropyridine N-oxide for selective reaction at the 3′-position. During the course of this work a general and rapid procedure was developed for the preparation and isolation of the 5′-dimethoxytrityl derivatives of the four common ribonucleosides. Silver ion was found to have a marked effect on dimethoxytritylation reactions.
The mechanisam of electrochemical reduction of N-haloamides in acetonitrile: trapping of intermediate amide anions and father–son protonation
Authors: Bérubé Denis , Lessard Jean
Published: May 2006

The electrochemical reduction of N-haloamides (ZCONRX) in acetonitrile involves two consecutive one-electron transfers and generates the amide anion. Attempts to trap the intermediate amidyl radical resulting from the first electron transfer were unsuccessful. In the case of the N-halo-N-hydroamides (R = H), the amide anion formed at the electrode abstracts a proton from an incoming N-halo-N-hydroamide molecule to give the parent amide and the conjugate base of the N-haloamide (father–son protonation). Thus, half of the N-halo-N-hydroamide reaching the electrode is reduced, the other half being converted to its conjugate base. In acetonitrile-LiClO4 (0.2 M) containing 0.2% water, the conjugate base is reducible and the polarograms therefore show two waves (irreversible and diffusion controlled) of equivalentintensities due respectively to the reduction of the N-halo-N-hydroamide and to the reduction of its conjugate base. In the case of the N-chloro-N-alkyl(aryl)amides (X = Cl, R = alkyl or aryl), the amide anion abstracts a proton from the medium to give the parent amide and anionic species that react with the starting N-chloroamide regenerating the amide anion. Hence, the coulometric results are low [Formula: see text] However, in the presence of acetic acid, the reduction consumes 2 F/mol as expected. The N-alkylamide anion has been trapped by N-alkylation and N-acylation. The voltammograms of N-chloro-N-alkyl(aryl)amides show multiple waves on mercury and platinum due to passivation–adsorption phenomena but a single wave on vitreous carbon.
Utilisation d'une méthode d'ajouts pour la détermination précise des volumes molaires partiels des constituants dans un solvant mixte. Application au système eau–méthanol
Authors: Letellier Pierre , Biquard Michel
Published: May 2006

The determination of partial molar volumes of each component in a binary mixture is usually the result of the derivation of the polynomial function which describes the whole excess curve. The accuracy of the present available densimeters (vibrating densimeter Piker type) allows direct access to the values of partial molar volume by a method requiring successive additions of various components. The method of calculation is discussed in this paper and applied for the water–methanol system. Partial molar volumes of water and methanol are calculated for different phase compositions, and each variation is described by polynomial functions which are related to each other by thermodynamic rules. This technique may be extended to mixtures which contain different solvents and highly concentrated solutes.
Spectres photoélectroniques de cyclohexène-2 ones-1 diversement substituées en position 3. Correlations avec la réactivité
Authors: Pfister-Guillouzo Geneviève , Geribaldi Serge , Gal Jean-François
Published: May 2006

We have recorded the photoelectronic spectra of 32 differently 3-substituted 2-cyclohexen-1-ones as well as those of 10 para-substituted acetophenones. Assignment of most of the cyclohexenone bands is made and the substituent effects on the π-electron ionization potentials and of the oxygen lone pair are discussed. The linear relationship between the ionization potential of the carbonyl oxygen lone pair and σp-type constants as well as those between the ionization potentials and the enthalpies of complexation (ΔH0) of the ketones with BF3 in methylene chloride allows us to propose that the direct conjugative interaction between the substituents and the carbonyl group is weak in the free ketone but becomes very strong in the complexed or protonated state. The existence of two distinct relationships (ΔH0 = f(PI n0) for 3-substituted cyclohexenones and the aromatic ketones indicates that this type of expression cannot be used for the comparison of the Lewis basicities of different types of ketones; on the contrary, these expressions do allow for the comparison of the relative basicities of the same type.

[Journal Translation]
Solvation of heterocyclic nitrogen compounds by methanol and water
Authors: Spencer J. N. , Holmboe E. S. , Kirshenbaum M. R. , Barton S. W. , Smith K. A. , Wolbach W. S. , Powell J. F. , Chorazy C.
Published: May 2006

The proton-donating and -accepting abilities of water and methanol to various nitrogen-containing compounds have been determined by calorimetric analysis. Water is a better proton donor than methanol but methanol is a better proton acceptor than water. The interactions by water and methanol at the nitrogens of the diazines follow trends expected from relative proton affinities, pK's, and theoretical calculations. Electrostatic interactions by the diazine nitrogens with pyridine parallel the interactions found for methanol and water at these nitrogens.
The generation and vibrational spectrum of matrix isolated thioformaldehyde and dideuterothioformaldehyde
Authors: Torres M. , Safarik I. , Clement A. , Strausz O. P.
Published: May 2006

The photolysis of inert matrix isolated methylene trithiocarbonate at 10 K has been shown to be a clean source of thioformaldehyde. The CH2S and CD2S molecules produced this way are indefinitely stable under these conditions and their FTIR spectra could be recorded. A normal coordinate analysis has been carried out and all the normal frequencies of both molecules have been assigned.
Metal hydride reductions of unsymmetrically substituted cyclic anhydrides attached to strained ring systems
Authors: Kayser Margaret M. , Salvador Judith , Morand Peter , Krishnamurty H. G.
Published: May 2006

A dramatic reversal in regioselectivity is observed in the metal hydride reduction of unsymmetrical cyclic anhydrides such as 2,3, and 4 compared to cyclic anhydrides attached to bridged ring systems (e.g. 1). The synthesis of model cyclic anhydrides attached to strained rings is described and the ratios of isomeric lactones obtained upon reduction with metal hydride are reported. On the basis of theoretical calculations and, taking into account the intrinsic reactivity of the carbonyl group, the antiperiplanar effect, and steric congestion, an explanation is offered for the regioselectivity observed in the reduction of these compounds.
The bromination–methanolysis of N-acetyl-2,3-dimethylindole
Authors: Vice Susan F. , Dmitrienko Gary I.
Published: May 2006

Bromination of N-acetyl-2,3-dimethylindole 11 in the presence of excess methanol at room temperature gave a mixture of products consisting of cis and transN-acetyl-2,3-dimethoxy-2,3-dimethylindoline 17 and 18,3-methoxy-2,3-dimethylindolenine 19, and N-acetyl-3-methoxymethyl-2-methylindole 21. The same reaction performed at −40 °C yielded a mixture of 17, 18, and N-acetyl-2-methoxy-2-methyl-3-methyleneindoline 22. Bromination of 11 at low temperature in the presence of 1.5 equivalents of methanol followed by treatment with triethylamine yielded 22 quantitatively. Treatment of 22 with acidic methanol readily gave 21. The mechanistic implications of these transformations are considered.
Isomerization of acetylenic acids with sodium salt of 1,2-diaminoethane: a one step synthesis of megatomoic acid
Authors: Abrams S. R.
Published: May 2006

A number of isomeric tetradecynoic acids were isomerized with the sodium salt of 1,2-diaminoethane. Isomers having the triple bond near the carboxyl group rearranged to E,Z-3,5- and E,E-3,5-tetradecadienoic acids (1 and 2), the former compound being the sex pheromone of the black carpet beetle. Isomers having the triple bond closer to the terminus of the chain afforded some 13-tetradecynoic acid along with 1 and 2. Delocalized anions 12 and 13 are thought to contribute to the formation of 1 and 2.
An iodine-127 Mössbauer study of some chalcogen cations of iodine
Authors: Birchall Thomas , Myers Ronald D. , Passmore Jack , Nandana W. A. Shantha , Sutherland George
Published: May 2006

The iodine-127 Mössbauer spectra of some chalcogen–iodine cations have been recorded and the Mössbauer parameters are discussed in terms of their known structures. These cations are compared to other cationic species of iodine as well as with a molecular compound of iodine which contains a sulphur–iodine bond.
Theoretical studies of SN2 transition states. Substituent effects
Authors: Wolfe Saul , Mitchell David John , Schlegel H. Bernhard
Published: May 2006

Similar substituent and angular constraint effects are noted for pyramidal inversion at tricoordinate nitrogen and inversion at a carbon centre undergoing an SN2 displacement reaction. The former process has been analyzed successfully by a quantitative PMO analysis which focuses on the frontier orbital interactions between X and NH2 in the planar and pyramidal structures of X—NH2 molecules having X = F, CH3, CHO. Based on total energy calculations at the 6-311G*//4-31G level, the effects of X upon the rates of the gas phase SN2 reactions F− + XCH2F → XCH2F + F− are found to be [Formula: see text]. Taking the treatment of nitrogen inversion as a precedent, the origin of this trend has been examined by a quantitative PMO analysis which focuses on the frontier orbital interactions between X and CH2F2− in the transition states, and between X and CH2F in the reactants. This has revealed that the rate enhancement associated with an α-carbonyl substituent in these SN2 reactions can be related to the presence of a stabilizing orbital interaction of a new type in the transition state, coupled to an exceptionally low destabilizing orbital interaction.
Nuclear magnetic resonance studies on the anions [M(SnCl3)5Cl]4− (M = Ru, Os) and [Ru(SnCl3)5(MeCN)]3−: the X-ray crystal structure of [N(C2H5)4]4[Ru(SnCl3)5Cl]
Authors: Farrugia Louis J. , James Brian R. , Lassigne Claude R. , Wells Edward J.
Published: May 2006

The octahedral anions [M(SnCl3)5Cl]4− (M = Ru, Os) have been fully characterized by 119Sn FT nmr spectroscopy. For M = Ru, 117Sn and 115Sn nmr spectra were also recorded, and an X-ray crystallographic study was carried out on the tetraethylammonium salt, isolated as a disolvate from acetonitrile. The Ru—Sn bond lengths indicate some degree of dπ–dπ interactions. The slight distortions from octahedral geometry are discussed in connection with the packing of the chlorine atoms. The Sn nmr spectra reveal the first observed coupling to a 99Ru nucleus (I = 5/2, 12.7% natural abundance), very large 2J(119Sn—117Sn) coupling constants, and the first observed second-order effects on a heteronuclear system. The octahedral anion [Ru(SnCl3)5(MeCN)]3− was also synthesized as the tetraethylammonium salt and characterized spectroscopically.
A surface tension approach to the salting-out of nonpolar nonelectrolytes
Authors: Aveyard Robert
Published: May 2006

A simple approach is developed for the salting-out of nonpolar molecules by strongly solvated salts. The standard free energy of transfer of solute from pure solvent to salt solution, and hence the salting coefficient, k, is calculated in terms of the surface tension increment caused by the addition of salt to the solvent. In its simplest form the method gives k in terms of the molar volumes of solvent and solute, and the osmotic coefficient of the salt solution. It is more successful in the prediction of k than the McDevit and Long theory, and it also has advantages over the more complex scaled particle theory of salt effects. In addition to a range of nonpolar solutes, the salt effects on some alcohols are also considered but application to polar solutes generally requires a knowledge of experimentally determined surface tension increments which are not widely available. The correct order of magnitude for the temperature coefficient of k at room temperature for some alkanes and H2 in water is given, although minima in k as a function of temperature, which have sometimes been observed, are not reproduced.
Charge distributions and chemical effects. XXIX. On the vibrational energies of chair and boat cyclohexane
Authors: Huvenne J. P. , Vergoten G. , Fleury G. , Odiot S. , Fliszár S.
Published: May 2006

Local symmetry force field calculations are presented for the chair and boat forms of cyclohexane and the assignments of frequencies are given. The calculated zero-point and thermal vibrational energies indicate a near invariance of total vibrational energy with respect to chair–boat conformational changes of the cyclohexane ring, thus confirming results of similar nature derived from earlier theoretical thermochemical analyses.
Simulation of edge-effects in electroanalytical experiments by orthogonal collocation.: Part 1. Two-dimensional collocation and theory for chronoamperometry
Authors: Speiser Bernd , Pons Stanley
Published: May 2006

A two-dimensional model to describe edge-effects at planar circular disc electrodes has been developed. Two-dimensional orthogonal collocation is used to discretize the corresponding partial differential equations. The equations for the simulation of a chronoamperometric experiment are derived.