Showing papers on "Diazomethane published in 1988"

p,p'-Dinitrobenzhydryl ethers, acid and base stable protecting groups, which are readily removable in the presence of benzyl and monomethoxytrityl functions

Abstract: Boron trifluoride-catalyzed reaction of bis(p-nitrophenyl)diazomethane (III) with alcohols such as (IV) gives the corresponding dinitrobenzhydryl ethers (V).

Studies on Sialic Acids.XIV.Lactone Derivatives of N -Acetylneuraminic Acid

Abstract: Benzoylation of N-acetylneuraminic acid (Neu5Ac) gave a variety of partially benzoylated bicyclic 1, 7-lactone derivatives and a perbenzoylated bicyclic 1, 4-lactone derivative in good yields. The structures of these compounds were elucidated mainly by means of proton nuclear magnetic resonance spectroscopy.Further, pivaloylation and ethoxycarbonylation of Neu5Ac also gave the corresponding acylated bicyclic lactone derivatives.These results allowed us to postulate a mechanism for the formation of bicyclic lactone derivatives in the acylation of Neu5Ac. Furthermore, treatment of Neu5Ac with diazomethane in an acidic methanol solution gave methyl a-D-neuraminoside methyl ester and a monocyclic 2-O-methyl-y-lactone derivative in 18% and 29% yields, respectively.These results provided information about the equilibrium of Neu5Ac in basic and acidic media.

Determination of butoxyacetic acid in urine by capillary gas chromatography

Abstract: A simple, rapid and reliable method is presented for the determination of butoxyacetic acid (BAA), the main metabolite of ethylene glycol monobutyl ether (Butyl Cellosolve). The urine is acidified with hydrochloric acid and passed through a cation-exchange column. BAA which is quantitatively found in the filtrate is subsequently adsorbed on XAD-4 resin. After desorption with diethyl ether an aliquot of the eluate is evaporated in a nitrogen stream and methylated with diazomethane in diethyl ether. A forty-fold enrichment is achieved by this procedure. The gas-chromatographic separation is performed on a 60 m fused silica capillary column DB-1 (100% dimethyl-polysiloxane). Flame ionization is used for detection. Pentoxyacetic acid (PAA) serves as internal standard. The detection limit of BAA in urine is 0.02 mg/l. Linearity has been tested up to 50 mg/l. The losses by the clean-up steps are between 10.0% and 22.7%. The average recovery is 100.9%. Within-series imprecision (n=10) has been determined for three concentrations and ranges between 4.8% and 12.6%.

A study of the generality of the reaction of diazomethane with halogenoplatinum(II) complexes in the preparation of (halogenomethyl)platinum(II) complexes

Abstract: Treatment of a range of platinum(II) halide (mainly chloride) complexes with diazomethane has been examined. Formation of both mono- and bis-halogenomethyl products has been observed. With one exception, methylene insertion appears to occur only when the metal–halogen bond is trans to a group of high trans influence (olefin, phosphine, isocyanide, alkyl, or hydride). With the trans-chlorohydrido derivatives investigated, the initially formed trans-(chloromethyl)hydrido products rearranged into the trans-(chloro)methyl species. Mechanisms of the methylene insertion and rearrangement processes are discussed.

1,2,3-Benzotriazine 2-oxides

Abstract: 4-Methoxy-1,2,3-benzotriazine, like the 4-methyl and 4-phenyl compounds, forms the 2-oxide on N-oxidation; this is hydrolysed to the acidic 3,4-dihydro-4-oxo-1,2,3-benzotriazine 2-oxide, which is N-methylated by diazomethane at the 3-position. The 4-methoxy 2-oxide was converted into 4-amino- and 4-hydrazine-derivatives. 5-Amino-3-methylisoxazole-2-carbonitrile forms 3,4-dihydro-5-methyl-4-oxoisoxazolo[5,4-d]-1,2,3-triazine 2-oxide on reaction with nitric and sulphuric acids. The 15N n.m.r. spectra of some 1,2,3-benzotriazines and their N-oxides are reported.

Selective Preferential Esterification of the Dicarboxylic Acids with Longer Carbon Chain by Diazomethane in the Presence of Dicarboxylic Acids with Shorter Carbon Chain by Adsorbing and Aligning the Acids on Alumina

Abstract: Selective monoesterification of a dicarboxylic acid with longer carbon chains by diazomethane in a mixture of dicarboxylic acids, [dodecanedioic acid (C12) plus glutaric acid (C5), adipic acid (C6), pimelic acid (C7), suberic acid (C8), or sebacic acid (C10)] was achieved by adsorbing and aligning the acids on alumina. The larger the difference in the number of carbon atoms, the higher the selectivity. In the case of the combination of C12 and C5 the highest selectivity was observed and the preferential 89% formation of the monomethyl ester of C12 was obtained in contrast to the 9% formation for the monomethyl ester of C5. Selective reactions were also observed in the case of the combination of C10 and C4, and that of C12 and trans-1,4-cyclohexanedicarboxylic acid.

Synthesis of a novel ferrocene derivative having flame-retardant and smoke-suppressant properties

Abstract: Reaction of ferrocene with chlorendic anhydride (1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic acid anhydride) under Friedel–Crafts reaction conditions affords a new monosubstituted dervative of ferrocene which has significant flameretardant and smoke-suppressant properties when incorporated into poly(vinyl chloride) (PVC). The monocarboxylic acid from the above reaction undergoes smooth methylation with diazomethane to give the corresponding methyl ester. 1H and 13C NMR spectra of these compounds have been compared with those obtained from similar compounds, namely β-ferrocenoylpropanoic acid and its methyl ester. Distant asymmetric centres in the chlorendic anhydride substituent markedly affect the proton spectra of the ferrocene derivative.

[2′,2′]-(+)-Catechin-(+)-taxifolin from commercial willow bark: structure, bonding positions and oxidative cleavage

Abstract: [2′,2′]-(+)-Catechin-(+)-taxifolin, a novel biflavonoid from commercial willow bark (Salix spp.), is characterized by spectrometric methods. The bonding positions are established by nuclear Overhauser effect difference spectroscopy of the methyl ether acetates of the bi-(+)-taxifolin analogues, which represent products of oxidation of the methylene function of the (+)-catechin moiety and which undergo methylene insertion reactions with diazomethane. Photoinduced oxidative cleavage of the biphenyl-type interflavonoid linkage involving singlet oxygen, accompanied by intermolecular transfer of an acetyl group of the peracetate, yielding a range of flavan-3-ols and dihydroflavonols, provides the first example of this type of biflavonoid photofragmentation.

Cyclopropanation of unsaturated fatty acid methyl esters using diazomethane and palladium (II) acetate

Abstract: Cyclopropanation of methyl esters of 10-undecenoic, oleic, elaidic, erucic,trans-2-docosenoic and a mixture of hydnocarpic and chaulmoogric acids was effected using diazomethane in the presence of palladium (II) acetate as catalyst. The products were isolated by silver ion thin-layer chromatography and characterized by infrared, proton nuclear magnetic resonance and mass spectrometric techniques. Terminally unsaturated, α, β-unsaturated and cyclopentene fatty acid esters were found to be more reactive than elaidate which in turn was more reactive than oleate. The reaction proceeds stereospecifically under milder conditions in a shorter time than with diiodomethane and zinc-copper couple.

1,3-Dipolar cycloaddition of diazomethane to differently substituted 2-methylpyridazin-3(2H)-ones

Abstract: Obtention d'adduits non stables se transformant en dimethyl 5H-pyrazolo [3,4-d] pyridazones-4 ou dimethyl 2H-pyridazones-3

Carbon-13 labelling study of the coenzyme B12-dependent methylitaconate ⇌α-methyleneglutarate model rearrangement reaction and examination of potential cyclopropane intermediates

Abstract: The model rearrangement mimicking the coenzyme B12-dependent, enzyme-catalysed interconversion of α-methyleneglutaric acid with methlitaconic acid has been carried out with a carbon-13 label. This experiment demonstrates beyond doubt that the acrylate group is the migrating group in the model, as it is in the enzyme-catalysed rearrangement. Experiments designed to probe the possible occurrence of cyclopropylmethyl intermediates in the model rearrangement are also described. To this end the cis- and trans-bromomethylcyclopropanediacids (16a) and (20a) were prepared starting from the common precursor cyclopropane-1,1,2-tricarboxylic acid (13). Thus, (13) was converted into the anhydride (14) which was, in turn, reduced to the lactone (15). Opening of the lactone with HBr in acetic acid gave the desired trans-diacid (16a). For the cis-diacid (20a), the anhydride (14) was hydrolysed, esterified with diazomethane, then reduced with lithium triethylborohydride. Conversion of the resulting alcohol (19) into the bromide (20a) was effected with phosphorus tribromide. An extensive series of experiments involving treatment of the acids and their methyl and tetrahydropyranyl esters with vitamin B12S was carried out. No methylitaconic acid (3a) could be detected in any of the reaction mixtures. However, α-methyleneglutaric acid (2a) and methylglutaconic acid (21) were observed as the reaction products. The methyl toluene-p-sulphonate (22) and iodide (23) were also examined and yielded results analogous to those obtained with the bromides.

Cycloaddition reactions of cephalosporin compounds. IX—1H and 13C NMR stereochemical study of the 1,3-dipolar cycloadditions of diazoalkanes to 2-methylenecephem derivatives†

Abstract: A series of known and novel 2-methylenecephem derivatives were prepared and their reactions with diazomethane, phenyldiazomethane and diphenyldiazomethane were studied. The initially formed 1-pyrazolino derivatives easily underwent spontaneous loss of nitrogen, leading to 2-spirocyclopropylcephems. The two reaction products, formed in a 3:1 to 8:1 ratio on addition of diphenyldiazomethane, were separated by column chromatography and distinguished by their 1H and 13C NMR spectra. The 1H NMR spectra did not exclude the possibility of 1-pyrazoline formation, but elemental analysis and 13C data corroborated the previous assumption that loss of nitrogen took place, even in those cases when it did not occur during the reaction.

Unprecedented reactivity of vinylidene complexes with diazomethane: insertion of the methylene group into a C–H bond

Abstract: [(η-C5H5)Ru{Ph2PCH(Me)CH(Me)PPh2}(CCHR)]PF6(R = Ph or But) react with diazomethane to give the corresponding methylvinylidene complexes [(η-C5H5)Ru{Ph2PCH(Me)CH(Me)PPh2}{CC(Me)R}]PF6; this novel type of reactivity suggests an alternative mechanism for the formation of branched hydrocarbons in the Fischer–Tropsch synthesis.

Transnitrosating activity of N-nitroso-N-methyl-p-toluenesulfonamide in rats and human gastric juice.

Abstract: N-nitroso-N-methyl-p-toluenesulfonamide (NMTS, diazald, CAS 80-11-5) is a widely used compound for laboratory production of diazomethane. The present results showed that the noncarcinogenic NMTS reacts as a transnitrosating agent with amino nitrogen of secondary amines and amide both in vitro (human gastric juice) and in vivo (rats) to yield N-nitroso compounds. Since all compounds formed (NMOR, NDMA, NPIP, NPZ, NMU) are known animal carcinogens, caution should be taken by users handling NMTS.

Production of ether solution of diazomethane

Abstract: PURPOSE:To obtain a compound useful as a methylesterifying agent keeping effect for a long period by simple operation in high yield, by purifying diazomethane with an ether and dissolving in another ether CONSTITUTION:p-Toluenesulfonyl-N-methyl-N-nitrosoamide is reacted with an alcohol such as methanol, etc, in the presence of an alkali (eg NaOH) to give a diazomethane gas Then the gas is brought into contact with dimethyl ether and, after the contact, the diazomethane gas is passed through a trap to remove impurities Further the gas is dissolved in another ether to give the aimed substance The concentration of diazomethane in the ether solution is 1-5wt% and the solution preferably has appearance of showing light lemon