Showing papers on "Diazomethane published in 2004"
TL;DR: The full spectroscopic characterisation of compounds 1-3 by NMR, UV, IR and MS data is reported, which shows the crystalline compound 2,8-dimethoxy-6-methyl-9-oxo-9H-xanthene-1-carboxylic acid methyl ester was determined by single crystal X-ray analysis.
68 citations
TL;DR: In this article, a variety of substrates including linear, cyclic, heterocyclic alkenes and their derivatives were tested in the liquid phase non-catalytic oxidation with nitrous oxide (N2O).
Abstract: A variety of substrates including linear, cyclic, heterocyclic alkenes and their derivatives were tested in the liquid phase non-catalytic oxidation with nitrous oxide (N2O). The structure and composition of the alkenes have a significant effect on the reaction selectivity. With many alkenes, N2O oxidation provides a selective way for the preparation of carbonyl compounds. The generation of carbene (or diazomethane) species is a remarkable feature of the oxidation of terminal alkenes.
65 citations
TL;DR: In this paper, the reaction of a variety of methyl esters with dimethylsulfoxonium methylide at 0-25 degrees C affords the chain-extended beta-keto dimethyl sulfoxideonium ylides.
Abstract: The reaction of a variety of methyl esters with dimethylsulfoxonium methylide at 0-25 degrees C affords the chain-extended beta-keto dimethylsulfoxonium ylides. Subsequent treatment with hydrogen chloride in THF proceeds with loss of DMSO to afford the corresponding alpha-chloroketones. This sequence has been utilized to convert the methyl esters of CBZ-protected alanine and valine to the anti N-protected alpha-amino epoxides, which are important pharmaceutical intermediates. When the same protocol is applied to BOC-protected phenylalanine methyl ester, epimerization occurs so that the use of a more reactive aryl ester is required. This chemistry provides a practical route to alpha-chloroketones that avoids the use of toxic and explosive diazomethane.
57 citations
TL;DR: St Stimulated by the favorable therapeutic properties of temozolomide, the designed and synthesized DNA-methylating triazenes built on the antiresistance benzylguanine ring system and found the condensation reaction between 2-nitrosopurines and acylhydrazines proved to be very suitable to prepare acylated methyltriazenes.
Abstract: Active resistance of tumor cells against DNA alkylating agents arises by the production of high levels of the DNA repair protein O6-alkylguanine-DNA alkyltransferase (AGT). This resistance during treatment with, for example, the anticancer agent temozolomide can be reversed by administration of O6-benzylguanine, a purine that transfers its benzyl group to AGT and irreversibly inactivates it. Stimulated by the favorable therapeutic properties of temozolomide we designed and synthesized DNA-methylating triazenes built on the antiresistance benzylguanine ring system. The condensation reaction between 2-nitrosopurines and acylhydrazines proved to be very suitable to prepare acylated methyltriazenes. Fine-tuning of the release rate of both the methylating agent (diazomethane) and of O6-benzylguanine was accomplished by variation of the hydrolysis-sensitive acyl substituent in 5. Hydrolysis studies were performed with 1H NMR and revealed that the p-nitrophenyl substituted triazene 26 showed an optimal hydrolysi...
55 citations
TL;DR: In this article, the physical properties of the new tetrazene were determined by drop hammer and combined IR and MS pyrolysis experiments, and the structure and bonding were discussed on the basis of X-ray, MO and NBO analysis.
Abstract: 1,4-bis-[1-methyltetrazol-5-yl]-1,4-dimethyl-2-tetrazene a formal hexamer of diazomethane can be viewed as a new stable high energy density material (HEDM) with the properties necessary for a potential green chemistry gas generator. The physical properties of the new tetrazene were determined by drop hammer and combined IR and MS pyrolysis experiments. The structure and bonding are discussed on the basis of X-ray, MO and NBO analysis.
53 citations
TL;DR: The ruthenium catalyst RuCl(NO)(PPh3)2 is shown to be an active catalyst for the methylenation of aldehydes in the presence of (trimethylsilyl)diazomethane, triphenylphosphine, and 2-propanol.
34 citations
TL;DR: The finding unequivocally shows that a precursor diazo unit can basically be handled as a building block to construct ploydiazo compounds and that persistent triplet carbenes, even though they greatly lose typical reactivity as a triplet carbene, still retain electronic properties and act as a spin source when aligned properly in the pi-electron frameworks to generate a high-spin molecule with remarkable thermal stability.
Abstract: [9-{10-(4-tert-Butyl-2,6-dimethyl)phenyl}anthryl](4-bromo-2,6-dimethylphenyl)diazomethane was found to be stable enough to survive under Suzuki coupling conditions and underwent mono-, di-, and trisubstitution with benzene mono-, di-, and triboronic acids to afford benzene derivatives having one, two, and three diazo units, respectively. The products from irradiation of those diazo compounds were characterized by ESR and SQUID measurements, which revealed that triplet, quintet, and septet ground states were formed from mono-, bis-, and tris(diazo) compounds, respectively. The stability of those high-spin species was estimated by temperature-dependent ESR and UV/vis measurements as well as laser flash photolysis, which indicated that all three species are stable up to 160 K and have a half-life of a few seconds in solution at room temperature. The finding unequivocally shows that a precursor diazo unit can basically be handled as a building block to construct ploydiazo compounds and that persistent triplet...
34 citations
TL;DR: In this paper, (trimethylsilyl)diazomethane has been selectively carbonylated to (trimsilyl)-ketene at 10°C under atmospheric pressure of carbon monoxide in the presence of octacarbonyl dicobalt as the catalyst.
Abstract: (Trimethylsilyl)diazomethane has been selectively carbonylated to (trimethylsilyl)ketene at 10 °C under atmospheric pressure of carbon monoxide in the presence of octacarbonyl dicobalt as the catalyst. The rate of (trimethylsilyl)ketene formation is first order with respect to both (trimethylsilyl)diazomethane and octacarbonyl dicobalt, and negative first order with respect to carbon monoxide.
24 citations
TL;DR: In this article, the reactivities of various double bonds in fluorine-containing unsaturated compounds toward cyclopropanation with diazomethane and methyl diazoacetate with catalysis by copper, rhodium and palladium compounds were studied.
24 citations
TL;DR: In this paper, a cycloaddition of diethyl 1-diazomethylphosphonate onto a C N double bond is described, and it was found that the reaction of this phosphorus diazomethsane with benzylidene-alkyl-amines resulted in the formation of (1alkyl 5-phenyl-4,5-dihydro-1 H -[1,2,3]triazol-4-yl)-phosphonic acid diethymers.
24 citations
TL;DR: In this article, the disjoint-nondisjoint concept was used to characterize the spin states of carbenes generated by the photolysis of these dendrimers, and the magnetic susceptibility of the photoproducts was measured.
TL;DR: In this paper, an improved synthesis of N-isocyanoiminotriphenylphosphorane is reported, which is a safe, stable, solid alternative to diazomethane and TMS-diazomethsane in the Arndt-Eistert synthesis of diazoketones.
Abstract: An improved synthesis of N-isocyanoiminotriphenylphosphorane is reported. This reagent is a safe, stable, solid alternative to diazomethane and TMS-diazomethane in the Arndt-Eistert synthesis of diazoketones.
TL;DR: In this paper, a three-step procedure was developed for the synthesis of 3,5-disubstituted methyl pyridazine-4-carboxylates from accessible 2,3-dissubstitized 2-cyclopropenecarboxylate.
Abstract: A three-step procedure has been developed for the synthesis of 3,5-disubstituted methyl pyridazine-4-carboxylates from accessible 2,3-disubstituted 2-cyclopropenecarboxylates. In the first step, cyclopropene derivatives react with diazomethane to give adducts having 2,3-diazabicyclo[3.1.1]hex-2-ene structure. The regio- and stereoselectivity of the cycloaddition has been determined. The second step is isomerization of the bicyclic adducts into 1,4-dihydropyridazine derivatives by the action of sodium methoxide. Finally, oxidation with potassium permanganate yields the target pyridazine-4-carboxylates.
TL;DR: Derivatization of orotic acid into various forms (trimethylsilylderivate, alkyl ester and per-methylated derivate) and their evaluation by GC/MS is described and application of the method on the patient with defect of ornithine transcarbamylase (OTC) was demonstrated.
TL;DR: Base-catalyzed self-condensation of 3,5-dimethoxyhomophthalic acid directly furnished the 6,8-dihydroxy-3-(2′-acetyl-3′,5′- dihydroxyphenyl)methylisocoumarin related to the natural product feralolide.
TL;DR: In this article, the two-step synthesis of tetraarylethylenes from benzophenones from diaryldiazomethanes has been studied, and the results show that 1,3,4-selenadiazoline intermediates and retrocyclization are obtained.
TL;DR: Bis(carbene) generated by irradiation of the bis(diazo) compound generated a fairly persistent S = 2 quintet state.
TL;DR: The synthesis, mass spectra and detectability of four selected dicarboxylic degradation products (CAPECs) of nonylphenol polyethoxylates (NPEOs) are reported, and the potential for the identification and quantification of individual branched carboxyalkyl isomeric mixtures based on corresponding dm-CA5-8P1ECs revealed the advantage of the GC-CI-MS.
TL;DR: In this article, X-ray crystallographic structures were determined for five diphenyldiazomethanes (DDMs) with various ortho substituents, namely, bis(2,4,6-trichlorophenyl)diazomet H 2, bis(4,tert-butyl-2,6)-trifluoromethyl)phenyl, bis (4-tert,butyl)-2.6-dibromophenyl), bis( 4-bromphenyl)-dimethylphenyl), and
TL;DR: Diazomethane and ethyl diazoacetate add to (E)-2-arylmethylene in a regio-and stereoselective fashion, yielding the corresponding 4'-aryl-1,2,3,4,4',5'-hexahydro-3'H-naphthalene-2-spiro-3'-pyrazol-1-ones.
Abstract: Diazomethane and ethyl diazoacetate add to (E)-2-arylmethylene-1,2,3,4-tetrahydronaphthalen-1-ones in a regio- and stereoselective fashion, yielding the corresponding 4'-aryl-1,2,3,4,4',5'-hexahydro-3'H-naphthalene-2-spiro-3'-pyrazol-1-ones. The products formed by addition of ethyl diazoacetate undergo isomerization into 4,5-dihydro-1H-pyrazole derivatives.
TL;DR: In this article, the rate constants for diazomethane, diazoethane and 1-diazopropane in aqueous 5% acetonitrile at 25°C and ionic strength 1'M (NaClO4) were measured by stopped-flow spectrophotometry.
TL;DR: In this paper, it was shown that irradiation (λ > 300 nm) of di(9-anthryl)diazomethane (1) in degassed benzene gave the trimer of dianthryl carbene (2) as the main product along with a small amount of a tetramer.
Abstract: Irradiation (λ > 300 nm) of di(9-anthryl)diazomethane (1) in degassed benzene gave the trimer (3) of dianthrylcarbene (2) as the main product along with a small amount of a tetramer (4). The struct...
TL;DR: Both of the bis(carbenes), 3 and 4, have a singlet quinoidal diradical ground state with a very small singlet-triplet energy gap of less than 1 kcal/mol, which indicates that bis( carbenes) are thermodynamically stabilized as a result of delocalization of unpaired electrons throughout a pi-net framework.
Abstract: [9-{10-(4-t-Butyl-2,6-dimethyl)phenyl}anthryl](4-bromo-2,6-dimethylphenyl)diazomethane (1−N2) was found to be stable enough to survive under Sonogashira and Suzuki coupling reaction conditions, and bis(diazo) compounds incorporated into the 1,4-positions of butadiyne (3−2N2) and the 2,5-position of thiophene (4−2N2) were prepared. Irradiation of those bis(diazo) compounds generated bis(carbenes), which were characterized by ESR and UV−vis spectroscopic techniques in a matrix at low temperature, as well as time-resolved UV−vis spectroscopy in solution at room temperature. These studies revealed that both of the bis(carbenes), 3 and 4, have a singlet quinoidal diradical ground state with a very small singlet−triplet energy gap of less than 1 kcal/mol. A remarkable increase in the lifetime of bis(carbenes) as opposed to that of monocarbene (1) was noted and was interpreted to indicate that bis(carbenes) are thermodynamically stabilized as a result of delocalization of unpaired electrons throughout a π-net fr...
TL;DR: In this paper, N-Nosyl-α-amino acid methyl esters are methylated with diazomethane and coupled with N-Fmoc amino acid chlorides to afford the corresponding dipeptides.
Abstract: N-Nosyl-α-amino acid methyl esters are methylated quantitatively with diazomethane. After proper deprotection of the amino function by treatment with the reagent system mercaptoacetic acid/sodium methoxide, the obtained N-methyl amino acid methyl esters are coupled with N-Fmoc amino acid chlorides to afford the corresponding dipeptides. The obtained products do not show any detectable extent of racemization by 1H NMR and HPLC.
TL;DR: Although ESR data indicated that ethynyl groups at the ortho positions are likely to stabilize triplet DPCs both sterically and electronically more effectively than o-bromine groups, kinetic studies suggested that the stability of tripletDPCs is not increased by o-ethynylgroups, as opposed to o- bromine Groups.
Abstract: (2,4,6-Tribromophenyl)(4-tert-butyl-2,6-dimethylphenyl)diazomethane (1a) was shown to be stable enough to survive Sonogashira coupling reaction conditions at an elevated temperature and gave not on
TL;DR: In this paper, the double bond at the methyl group of 2-fluoro-3-methylbuta-1,3-diene with diazomethane in ether at 15 °C and with Diazocyclopropane generated in situ by decomposition of N-cyclopropyl-N-nitrosourea in the presence of K2CO3 in CH2Cl2 at -10 °C selectively involve the double-body to give 3-methylpyrazolines.
Abstract: Reactions of 2-fluoro-3-methylbuta-1,3-diene with diazomethane in ether at 15 °C and with diazocyclopropane generated in situ by decomposition of N-cyclopropyl-N-nitrosourea in the presence of K2CO3 in CH2Cl2 at –10 °C selectively involve the double bond at the methyl group to give 3-(1-fluorovinyl)-3-methylpyrazolines. Thermal dediazotization of the latter at 250 °C yields 1-(1-fluorovinyl)-1-methylcyclopropane and -spiropentane 5, which are capable of isomerizing, under more severe conditions (400—600 °C), into 1-fluoro-2-methylcyclopent-1-ene and 5-fluoro-4-methylspiro[2.4]hept-4-ene (7), respectively. Spiropentane derivative 5 partially isomerizes into 1-fluoro-2-methyl-3-methylidenecyclohex-1-ene. In a similar way, thermolysis of 6-(2,3,3-trifluorocyclobut-1-enyl)-4,5-diazaspiro[2.4]hept-4-ene at 400 °C gives a mixture of 1-(spiropentyl)-2,3,3-trifluorocyclobut-1-ene and 2,3,3-trifluoro-1-(2-methylidenecyclobutyl)cyclobut-1-ene. Thermolysis of 1-cyclopropyl-2,3,3-trifluorocyclobut-1-ene at 550—620 °C affords a mixture of 1-(trifluorovinyl)cyclopentene and 2,3-difluorotoluene.
TL;DR: Admixture of vicinal di-, tri-, and tetraketones with ethereal diazomethane results in one-time methylene transfer to the less hindered face of the sterically most accessible and electron-deficient carbonyl group as mentioned in this paper.
Abstract: Admixture of vicinal di-, tri-, and tetraketones with ethereal diazomethane results in one-time methylene transfer to the less hindered face of the sterically most accessible and electron-deficient carbonyl group to deliver epoxy ketones in a highly selective manner unless ring strain effects contravene.
TL;DR: In this paper, the authors proposed a completely stereoselective approach to each of these useful synthons that avoids the need for any chromatographic or other separation of isomers and which can be conducted on scales comparable to those reported earlier.
29 Apr 2004
TL;DR: In this article, a variety of substrates including linear, cyclic, heterocyclic alkenes and their derivatives were tested in the liquid phase non-catalytic oxidation with nitrous oxide (N2O).
Abstract: A variety of substrates including linear, cyclic, heterocyclic alkenes and their derivatives were tested in the liquid phase non-catalytic oxidation with nitrous oxide (N2O). The structure and composition of the alkenes have a significant effect on the reaction selectivity. With many alkenes, N2O oxidation provides a selective way for the preparation of carbonyl compounds. The generation of carbene (or diazomethane) species is a remarkable feature of the oxidation of terminal alkenes.