Showing papers on "Diazomethane published in 1992"
68 citations
TL;DR: In this article, it was shown that 4 is not the direct precursor for 5 in the photolysis of 3, suggesting that 4 was not a direct precursor to 5 in 3.
Abstract: Irradiation (λ>350 nm) of (2-nitrophenyl)diazomethane (1) matrix-isolated in Ar at 10 K provided 2-nitrosobenzaldehyde (3) presumably as a result of intramolecular oxygen migration in (2-nitrophenyl)carbene (2). Upon further irradiation (λ 300 nm) but not at longer wavelength (λ>350 nm), suggesting 4 is not the direct precursor for 5 in the photolysis of 3
46 citations
TL;DR: In this article, a method was described to determine nitrophenols and two herbicides (Bromoxynil, Ioxynin) in precipitation, with GC-PND and GC-MS.
Abstract: A method is described to determine nitrophenols and two herbicides (Bromoxynil, Ioxynil) in precipitation, with GC-PND and GC-MS. First, the micropollutants were extracted by a mixture of pentane and ether (1/1), concentrated by rotary evaporator, then methylated by diazomethane. The extraction and reaction yields were measured. The resulting recoveries were between 75 and 100% for the mononitrophenols and about 70% for methylnitrophenols. The detection limits were about 0.25 μg/l for most substances.
33 citations
TL;DR: In this paper, an asymmetric synthesis of (+)-(1R, 2S)-allocoronamic acid was reported, where Diazomethane addition to (Z)-N-( tert -butoxycarbonyl)ethyldehydroalanyl-L-prolin-anhydride, easily prepared from 2-phenyl-4-propylidene-5(4H)-oxazolone and L-proline, gave in high diastereomeric excess the corresponding spiropyrazoline, which was transformed, on photo
32 citations
TL;DR: In this paper, N,N-Dibenzlamino aldehydes, readily accessible from amino acids, can be converted into λ-N,Ndibenzylamino α,β-didehydro amino acid esters without racemization.
31 citations
TL;DR: Fluorination of methyl (1R,3R,4S)-8-phenylmenthyl methylmalonates using lithium hexamethyl-disilazide and 1-fluoro-2,4,6-trimethylpyridinium triflate (trifluoromethanesulfonate) gave the (R)-3 and (S)-4 isomers in a 3.8 : 1 ratio, while fluorination of ethyl-, propyl- and benzyl-malonsates 10, 11 and 12 provided
Abstract: Fluorination of methyl (1R,3R,4S)-8-phenylmenthyl methylmalonates 2 using lithium hexamethyl-disilazide and 1-fluoro-2,4,6-trimethylpyridinium triflate (trifluoromethanesulfonate), gave the (R)-3 and (S)-4 isomers in a 3.8 : 1 ratio, while fluorination of ethyl-, propyl- and benzyl-malonates 10, 11 and 12 provided the (R)-13, 15 and 17 and (S)-14, 16 and 18 isomers in a 1 : 1.6–2.0 ratio. On the other hand, alkylation of (1R,3R,4S)-8-phenylmenthyl hydrogen fluoromalonates 26 in the presence of lithium hexamethyldisilazide, followed by esterification with diazomethane, produced the (R)-3,13,15,17- and 27 and (S)-4,14,16,18 and 28 isomers in a 1 : 5.7–35 ratio.
24 citations
TL;DR: The lithium salt of [bis(dicyclohexylamino)phosphanyl]diazomethane (7) reacts with bis(diclohexyamino)chlorophosphane (8) leading to a mixture of nitrilimine 9 and diazo derivative 10, in a 21/4 ratio.
Abstract: The lithium salt of [bis(dicyclohexylamino)phosphanyl]diazomethane (7) reacts with bis(diclohexylamino)chlorophosphane (8) leading to a mixture of nitrilimine 9 and diazo derivative 10, in a 21/4 ratio. The reaction of [bis-(diisopropylamino)thioxophosphoranyl](triethylstannyl)diazomethane (11) with bis(diisopropylamino)chloroborane (12) gives C-[bis(diisopropylamino)thioxophosphoranyl]-N-[bis(diisopropylamino)boryl]nitrilimine (13), in 60% yield
22 citations
TL;DR: In this paper, the cycloaddition reaction of 3-phenylsydnone with the stannylacetylenes with tributylstannyl chloride was investigated.
Abstract: 1,3-Dipolar cycloaddition reaction of diazomethane and ethyl diazoacetate with tributylstannyl-acetylenes occurred regioselectively to afford the corresponding 3(5)-tributylstannylpyrazoles. The cycloaddition reaction of 3-phenylsydnone with the stannylacetylenes proceeded also regioselectively, and 3-tributylstannyl-1-phenylpyrazoles were isolated. 4-Tributylstannyl- and 5-tributylstannyl-1-phenylpyrazole were prepared by the stannylation of 4-lithio- and 5-lithio-1-phenylpyrazoles with tributylstannyl chloride. Iodination, benzoylation, and phenylation of the stannylpyrazoles were examined
20 citations
TL;DR: Full 1H and 13C NMR assignments are presented for 12 new compounds and a remarkably specific and efficient side-chain oxidation of I was found.
20 citations
TL;DR: The synthesis of the title compounds is easily achieved by the Pd-catalysed cyclopropanation of unsaturated compounds with diazomethane generated in situ from N-methyl-N-nitrosourea-KOH in CH2Cl2-Et2O as mentioned in this paper.
19 citations
TL;DR: In this article, a chiral intermediate for the preparation of calyculins was synthesized starting from (S)-pyroglutaminol via the O-methylation of 1c with diazomethane in the presence of fluoboric acid and cis-dihydroxylation of the α, β-unsaturated lactam.
Abstract: (3R, 4R, 5R)-1-(tert-Butoxycarbonyl)-3, 4-isopropylidenedioxy-5-methoxymethyl-2-pyrrolidinone (6), a useful chiral intermediate for the preparation of calyculins, was synthesized starting from (S)-pyroglutaminol via the O-methylation of 1c with diazomethane in the presence of fluoboric acid and cis-dihydroxylation of the α, β-unsaturated lactam (4) as the key reactions.
TL;DR: Optically pure 2-(fluoromethyl)-2-[(4-methylphenylsulphinyl)methyl]oxirane has been obtained in good yield and with high d. as discussed by the authors.
TL;DR: In this article, the reactivities and the regioselectivities of S and Se in the formation and dissociation of the alkylidene-adducts are discussed.
Abstract: Dichalcogenolatocobalt complexes CpCo(X1X2C2Ph2) (1: X1 = X2 = S; 2: X1 = X2 = Se; 3: X1 = S, X2 = Se) react with diazomethane or ethyl diazoacetate to yield 1:1 alkylidene-adducts CpCo[η3-(X1 , X2 , C)-{X1C(Ph)-C(Ph)X2CHR}] (4–9) with the evolution of N2. Thermal reaction of 9 (X1 = S, X2 = Se, R = CO2Et) causes isomerization to 8 (X1 = Se, X 2 = S, R = CO2Et). The reactivities and the regioselectivities of S and Se in the formation and dissociation of the alkylidene-adducts are discussed. 77Se NMR spectroscopy of the alkylidene-adducts was also studied.
TL;DR: In this paper, the 4-oxo-5-OTBDMS-Avermectin B 1 (2 ) was treated with trimethylsilyldiazomethane or diazomethelane to obtain the stereoselective formation of 4-4-a-oxide (3 ) in addition to ringexpanded oxepinyl epoxide (4 ).
TL;DR: In this article, the cyclic hexafluoroacetone ketals 3 and 6 of the title compounds 1 and 5 were prepared with HFA in the presence of dicyclohexyl carbodiimide (DCC).
TL;DR: In this paper, the title compound was obtained in low yield using 2-hydroxymethyl-1-methyl-5-nitroimidazole-2-carbonyl)acetate.
TL;DR: In this paper, the guanosine nucleosides can be converted directly to their 2′-0-methyl derivatives by methylation with trimethylsilyldiazomethane in the presence of stannous chloride.
Abstract: Protected guanosine nucleosides can be converted directly to their 2′-0-methyl derivatives by methylation with trimethylsilyldiazomethane in the presence of stannous chloride. This procedure circumvents the need to use the potentially hazardous reagent, diazomethane.
TL;DR: In this article, preferential methylation occurs at N-3 yielding the mesoionic compounds 9 and 12 The parent oxime 6a also furnishes the N-2 methylated product 8a in substantial amounts.
Abstract: 1,2,3-Thiadiazoles unsubstituted at the 4-position and bearing an oxime or phenylhydrazone function at the 5-position have been prepared and treated with Meerwein's reagent In all cases studied, preferential methylation occurs at N-3 yielding the mesoionic compounds 9 and 12 The parent oxime 6a also furnishes the N-2 methylated product 8a in substantial amounts In contrast, when the methylation of oxime 6a is carried out with diazomethane or with methyl iodide, the nitrone 10a and the oxime ether 11a are formed The isomeric structures of the reaction products were distinguished by their 13C NMR and mass spectra
TL;DR: CyCyclotrisulfimide (1,5,2,4,6- trithiatriazine-1,1,3,5-5-hexoxide) has been synthesized successfully from persilylated sulfanuric acid (2) and hydrogen chloride in dichloromethane and has been isolated in pure form as discussed by the authors.
Abstract: Cyclotrisulfimide (1,3,5,2,4,6- trithiatriazine-1,1,3,3,5,5-hexoxide) (1) has been synthesized successfully from persilylated sulfanuric acid (2) and hydrogen chloride in dichloromethane and has been isolated in pure form. Correlations of infrared and 15N-NMR spectra support assignment of the imide structure of (1). Ring cleavage appears to characterize reactions of (1) with solvolytic reagents. Thermal decomposition of (1) has been studied by TG accompanied by TLC methods. Reaction with diazomethane in dioxane yields the N,N,N-trimethyl derivative (3). Hitherto unknown (2) has been prepared from the trisilver salt of (1) using uimethylchlorosilane. The compound (2) has been characterized by IR, 15N-NMR and by X-ray crystallography. In the structure the S3N3 ring adopts a flattened chair conformation with the silyl groups being axial.
TL;DR: In this article, the thermal decomposition of di(tert-butyl)diazomethane was investigated under nearly unimolecular conditions and the N2 elimination at the surface of contacts.
Abstract: Di(tert-butyl)diazomethane: Thermal Decomposition and One-Electron Redox Reactions.
Di(tert-butyl)diazomethane is a potential precursor for the still unknown, presumably sterically overcrowded tetrakis(tert-butyl)ethane and, therefore, re-investigated. Its (Hel) photoelectron spectrum exhibits a low first vertical ionization energy of only 7.45 eV. Based on the ionization pattern, both the thermal decomposition above 600 K under nearly unimolecular conditions as well as the N2 elimination at the surface of contacts, [Nix/C]∞, [Rh4(CO)12/SiO2]∞, [Rhx/SiO2]∞, and [Ag2CO3]∞ are analyzed in a flow-system. Heterogeneously catalyzed, N2 is split off already at room temperature, but in contrast to results for sterically less shielded diazo compounds, no dimer is formed, and only mixtures of known di(tert-butyl)carbene-isomerization products are isolated. Cyclic voltammetry at 233 K using a glassy carbon electrode proves a reversible oxidation followed by N2 elimination at higher temperatures and an irreversible reduction. On chemical oxidation, however, no paramagnetic species can be detected, whereas chemical reduction at a potassium metal mirror in a THF solution containing (2.2.2)cryptand, yields the radical anion characterized by ESR spectroscopy. Without a cation-chelating ligand, the radical anion of a hitherto unknown dimer, ((CH3)3C)2CNNNNC(C(CH3)3) 2' ⊖, is generated, which dissociates at higher temperature, forming ((CH3)3C)2N2' ⊖. This one-electron reduction product of di(tert-butyl)diazomethane can also be detected after quickly warming up a solution containing presumably the radical anion of the triphenylphosphane adduct ((CH3)3C)2CNNPPh3' ⊖. In one of these reduction reactions, a N2 elimination is observed.
TL;DR: Treatment of silatranyl- and 3,7,10-trimethylsilatr-anyl-ethylenes with diazomethane/Pd(OAc)2 gives the corresponding SILATranylcyclopropanes in high yields.
TL;DR: In this article, photolysis of bis[bis(diisopropylamino)thioxophosphoranyl]diazomethane (1) in the presence of a slight excess of dimethyl acetylenedicarboxylate led to 1,3λ 5 -thiaphosphole 5 in 95% yield.
Abstract: Photolysis of bis[bis(diisopropylamino)thioxophosphoranyl]diazomethane (1) in the presence of a slight excess of dimethyl acetylenedicarboxylate led to 1,3λ 5 -thiaphosphole 5 in 95% yield. This compound was fully characterized including an X-ray diffraction study. Irradiation of (thioxophosphoranyl)(trimethylsilyl)diazomethane 2 gave rise to [bis(diisopropylamino)thioxophosphoranyl](trimethylsilyl)carbodiimide 6 in 60% yield
TL;DR: The reaction of perlauric acid with diazomethane is three orders of magnitude faster than that of tert -butyl hydroperoxide as mentioned in this paper, and the reaction conditions (195 and 273 K) are shown to transform Perlauric acids into products containing no active oxygen.
TL;DR: In this article, the 2-methyl derivatives of benz-indazolquinone were established by reaction of corresponding benzoquinones with 3-methylsydnon in the case of 4e,4g.
Abstract: Thep-benzoquinones5e-j react with diazomethane (after dehydrogenation) to 6-anilino-2e, dimethylamino-2h, phenylthio-2i, and methylthioindazolquinone2j. Methylation with dimethylsulfate of these as well as of the already known indazolquinones 6-toluidino-2f, 6-methylanilino-2g, 5-tert.butyl-2m, 5,6-methyl- (isomer mixture)2l,n, and benz-indazolquinone2o yield the 1-and 2-N-methyl derivatives3 and4. The structure of the 2-methyl derivatives is established by reaction of the corresponding benzoquinones with 3-methylsydnon in the case of4e,4g. UV/VIS-, IR- and1H-NMR-spectroscopy (in CDCl3 andDMSO) were used for structure determination. Comparison of the UV/VIS-spectra of2–4 shows that the indazolquinones are existing as 2 H-4,7-diones. For the structure elucidation of the 1- rs. 2-methylderivatives (whichh can be attributed to the methylation products) NMR-spectroscopy is well suited even without knowing the second isomer (solvent-effect). The course of the reaction of quinones with diazomethane and of the methylation reactions of the indazolquinones is discussed.
TL;DR: The carboxyl content of different fulvic acids was estimated by means of a methylation technique that involved methylation by diazomethane followed by base catalyzed hydrolysis, esterification with propionyl chloride and gas chromatographic analysis of the methyl ester formed.
TL;DR: In this article, the stereostructure of (1R*,6S*,8R*)-8-Methylsulfonyl-2-oxa-7-thiabicyclo[4.2.0]octane 7,7-dioxide was established by X-ray crystallography.
Abstract: (1R*,6S*,8R*)-8-Methylsulfonyl-2-oxa-7-thiabicyclo[4.2.0]octane 7,7-dioxide 10a, available from the reaction of 3,4-dihydro-2H-pyran and methylsulfonylsulfene 1(generated in situ from MeSO2Cl and Et3N), underwent alkylation at position 8 in the presence of sodium hydride and alkyl halides. With methyl iodide and chloromethyl methyl ether, mixtures of the endo- and exo-methyl derivatives 10b and 11b(with 10b in predominance) and the endo- and exo-methoxymethyl derivatives 10c and 11c(with 11c in predominance) were produced. With benzyl chloride, tert-butyl bromoacetate and allyl bromide, only the exo-alkyl derivatives 11d-f were isolated, the stereostructure of compound 11f being established by X-ray crystallography.In the presence of sodium thiophenoxide and thiophenol, compound 10a underwent a reductive cleavage of its S(7)–C(8) bond to give, after acidification, the sulfinic acid 9a; the sodium salt of the last-cited acid underwent methylation with methyl iodide to give (2S*,3S*)-3-methylsulfonyl-2-(methylsulfonylmethyl)tetrahydropyran 15d. Under corresponding conditions (and also in the presence of a large excess of Na/Hg in MeOH), compound 11f afforded the sulfinic acid 27c which was transformed into (2R*,3S*)-3-methylsulfonyl-2-[(1′R*)-1′-(methylsulfonyl)but-3′-enyl]-tetrahydropyran 21d; the stereostructure of the last cited compound was determined by X-ray crystallography. The sulfinic acid 27c also underwent reaction with diazomethane to give the methyl sulfinate 27b as a ∼ 1 : 1 mixture of diastereoisomers.In the presence of Raney nickel, compound 10a furnished (2R*)-2-(methylsulfonylmethyl)-tetrahydrofuran 14 whereas compound 11f underwent reduction of its olefinic linkage to give the propyl derivative 11h.Sodium methoxide in methanol (and also Na/Hg in MeOH) induced an overall hydrolytic cleavage of the S(7)–C(8) bonds of compounds 10a and 11f to give, after acidification, the cis-sulfonic acids 15c and 21b(which were isolated as their methyl esters 15a and 21a). In the presence of sodium hydroxide, the cis-sulfonic acid 15c underwent epimerisation at position 2 to give the trans-sulfonic acid 17c(which was isolated as its methyl ester 17a).
TL;DR: In this paper, the methyl cyclopropylacetate was prepared from allyl cyanide by the same method, which was later used to obtain the cycloprocessor.
TL;DR: The methyl ester of RITA which structurally corresponds to the parent compound methylphenidate is reextracted at pH 9-11 and use of diazomethane or sulphuric acid is replaced by the use of a less hazardous reagent.
TL;DR: The reaction of trithiocyanuric acid with 3 equivalents of 2-benzenesulfonyl-3-phenyl-oxaziridine affords the highly reactive 1,3,5- triazine-2,4,6-trisulfenic acid 3 which is trapped by reaction with diazomethane to give the trimethylester of 3.
Abstract: The reaction of trithiocyanuric acid 1 with 3 equivalents of 2- benzenesulfonyl-3-phenyl-oxaziridine affords the highly reactive 1,3,5- triazine-2,4,6-trisulfenic acid 3, which is trapped by reaction with diazomethane to give the trimethylester of 3. Additionally the reactions of trithioisocyanurates and trithiocyanurates with meta-chloroperbenzoic acid (mCPBA), oxaziridine, dimethyldioxirane and chlorine are studied.