Showing papers on "Diazomethane published in 2002"
TL;DR: Acidic methanol esterification followed by gas chromatography with electron capture detection was applied for the determination of the nine haloacetic acids in water, with the only exception being monochloroacetic acid.
60 citations
TL;DR: The reaction of lithium (trimethylsilyl)diazomethane with aldehydes and ketones has been investigated, and it has been found that quenching at low temperature with MeOH followed by addition of Rh2(OAc)4 gave silyl enol ethers in high yields.
Abstract: The reaction of lithium (trimethylsilyl)diazomethane with aldehydes and ketones has been investigated, and it has been found that quenching at low temperature with MeOH followed by addition of Rh2(OAc)4 gave silyl enol ethers in high yields. Quenching with other electrophiles (e.g., deuterium, MeI) gave terminal and substituted silyl enol ethers with complete control over regio- and stereochemistry. The mechanism of this novel process has been mapped out through a combination of deuterium labeling, ReactIR, and isolation of reaction intermediates.
54 citations
TL;DR: In this article, β-Nitro-meso-tetraphenylporphyrin reacts with diazomethane to give a pyrazoline-fused chlorin as the main product.
Abstract: β-Nitro-meso-tetraphenylporphyrin reacts with diazomethane to give a pyrazoline-fused chlorin as the main product. This compound was converted into the corresponding pyrazole-fused porphyrin, by treatment with DBU, and into a methanochlorin by refluxing in toluene.
41 citations
TL;DR: From the spectra of the modified and unmodified HA with carbon-13 of natural abundance it can be concluded that the applied preparative modification procedure causes only the desired structural changes in HA.
31 citations
TL;DR: Diazomethane reacts with hydrogen-terminated porous or single crystal silicon surfaces under irradiation with the 365 nm line from a mercury lamp as discussed by the authors, and the surface Si−Hx groups are lost and an HF-resist...
Abstract: Diazomethane reacts with hydrogen-terminated porous or single crystal silicon surfaces under irradiation with the 365 nm line from a mercury lamp. The surface Si−Hx groups are lost and an HF-resist...
24 citations
TL;DR: In this paper, the synthesis of indazol-4,7-dione derivatives via 1,3-dipolar cycloaddition of diazomethane with 2,3dimethyl-1,4-benzoquinone (2) and 1,4naphthoquinone(7) followed by N-alkylation of the pyrazol nitrogen atom of the corresponding quinones (3) and (8) with methyl chloroacetate is described.
21 citations
TL;DR: An enantioselective synthesis of the alpha,alpha-dialkyl-alpha-amino acid (1S,3R)-ACPD has been achieved using an alkylidene carbene 1,5-CH insertion reaction as a key step.
Abstract: An enantioselective synthesis of the α,α-dialkyl-α-amino acid (1S,3R)-ACPD has been achieved using an alkylidene carbene 1,5-CH insertion reaction as a key step. The ketone cyclization precursor was synthesized from Garner's aldehyde in high yield via a Wittig homologation and subsequent catalytic hydrogenation. Treatment of the ketone with 1.2 equiv of lithio(trimethylsilyl)diazomethane in THF resulted in the formation of the corresponding cyclopentene-containing CH-insertion product in 62−69% yield in high enantiomeric excess. Subsequent functional group manipulation allowed the synthesis of the amino acid (1S,3R)-ACPD to be completed.
19 citations
TL;DR: In this article, α,β-Unsaturated imines, obtained from cis -17-silyloxy-16-amino steroids and α, β-unsaturated aldehydes, react with diazomethane in the presence of a catalytic amount of Pd(OAc) 2 with high chemo- and diastereoselectivities to form steroidal cyclopropanocarbaldimines.
18 citations
TL;DR: The new ACC ester 14 was transformed into fused tetracyclic hydantoin derivatives, which comprised a new type of heterocyclic system that can be considered as a doubly constrained 1-aminocyclopropane-1-carboxylic acid system.
Abstract: Reaction of N-benzoyl-1,2,3,4-tetrahydroquinoline-2-carboxylic acid with acetic anhydride resulted in 1H,3H,5H-oxazolo[3,4-a]quinolin-3-one derivative 13. Different cyclopropanation processes were applied to 13, but only diazomethane in the presence of water furnished the hitherto unknown methyl 1,2,7,7a-tetrahydro-1aH-cyclopropa[b]quinoline-1a-carboxylate 14, which can be considered as a doubly constrained 1-aminocyclopropane-1-carboxylic acid system. The mechanism of the cyclopropanation was studied in detail. The new ACC ester 14 was transformed into fused tetracyclic hydantoin derivatives, which comprised a new type of heterocyclic system.
17 citations
TL;DR: In this paper, 3-aroyl-4-(3-chromonyl)-2-pyrazolines have been synthesized by the reaction of 3-aryl-3-oxo-propenyl)chromen-4-ones and diazomethane.
16 citations
TL;DR: The behavior of the title compounds in their reactions with diazomethane and diazoethane is reported in this article, where the π-facial selectivity is moderate, being controlled mainly by steric factors in the reactions involving the formation of N dipole ǫ-C(4) furanone bonds.
Abstract: The behavior of the title compounds in their reactions with diazomethane and diazoethane is reported. The reactivity of the 5-alkoxyfuran-2(5 H )-ones as dipolarophiles is dramatically enhanced by the presence of sulfur functionalities at C-4. The regioselectivity of the cycloadditions of diazomethane is opposite to that observed with diazoethane, due to control by the carbonyl group in the first case and by the sulfur function in the second case, with the sulfonyl group exhibiting a higher regio-orientating ability than the sulfinyl one. The π-facial selectivity is moderate, being controlled mainly by steric factors in the reactions involving the formation of N dipole C(4) furanone bonds, whereas the predominant role of electronic factors, modulated by the polarity of the solvent, leads to high stereoselectivities in processes involving the formation of N dipole C(3) furanone bonds. Finally, the endo / exo ratios from reactions with diazoethane can be rationalized on steric grounds.
TL;DR: The reaction of 10 carboxamides activated by two beta-electron-withdrawing groups with diazomethane was investigated and an approximate qualitative relationship exists between the acidity of the enol and K(enol) and the regioselectivity of the reaction.
Abstract: The reaction of 10 carboxamides activated by two β-electron-withdrawing groups, which mostly exist completely or partially in their enol forms, with diazomethane was investigated. The main outcome is the diversity of reactions observed. With the most acidic enols 3−7, activated by at least one trifluoroethoxycarbonyl group or a cyano group, O-methylation or O,N-dimethylation takes place. With β-dimethoxycarbonyl-activated systems 5 and 8, the C-methylation product of the amide form was one of the products. With a Meldrum's acid anilide enol 2, a cleavage took place leading to the C-alkylated imine having a CH(CO2Me)2 group. Exchange of one 2,2,2-trifluoroethoxycarbonyl by a methoxycarbonyl in the C,N-dimethylation product of Me2CHNHC(OH)C(CO2CH2CF3)2 4 took place. The 2-anilido-1,3-cyclopentanedione 10 was methylated on a ring carbonyl while the enol of the 1,3-indanedione analogue 11 reacted with three diazomethane molecules and underwent a ring expansion and O-methylation to the 3-anilido-1,4-dimethoxyn...
TL;DR: Tisler as mentioned in this paper gave (S)-5]-(E)-(dimethylamino)methylidene]-2-oxotetrahydrofuran-5-carboxylate (2) with potassium cyanide in acetic acid, which was used as chiral dipolarophile in 1,3-dipolar cycloadditions.
TL;DR: In this paper, the authors describe the synshesis of SPIRO-1-PYRAZOLINES by the reaction of Z-3-ARYLIDENE-1 -THIOFLAVANONES with DIAZOMETHANE.
TL;DR: The lithium enolates of trimethylsilyl but-3-enoate and 3-methylbut-3,enoate reacted with aldehydes and saturated or aromatic ketones at -70 degrees C to give exclusively the alpha-condensation products in excellent yields.
Abstract: The lithium enolates of trimethylsilyl but-3-enoate and 3-methylbut-3-enoate reacted with aldehydes and saturated or aromatic ketones at −70 °C to give exclusively the α-condensation products in excellent yields. The unsaturated β-hydroxy acids thus obtained were directly identified, and the usual conversion into their methyl esters with diazomethane was not necessary. Unsaturated ketones underwent Michael reaction through α-addition leading to the unsaturated 5-oxo acids.
Journal Article•
TL;DR: The tetracycline derivative was soluble in aqueous solvents and was stable for more than five weeks when stored at < or = 0 degrees C, indicating a lipophilic substituent.
Abstract: Tetracycline is a widely used broad spectrum antibiotic. A derivative of tetracycline was synthesized by methylation (-CH3) of the phenolic hydroxyl group, with the use of diazomethane (CH2N2). A methyl ether group is then formed from the reaction with diazomethane, which replaces the hydroxyl group. The newly formed derivative has reduced hydrogen bonding capability relative to the unmodified tetracycline. An infrared spectra shows the appearance of the ether group on the derivative and the Log P calculations indicate that the derivative has increased lipophilic tendency. The Lipophilic Substituent Constant calculated for the tetracycline derivative is 0.46, indicating a lipophilic substituent. The tetracycline derivative was soluble in aqueous solvents and was stable for more than five weeks when stored at < or = 0 degrees C. The derivative was placed in tissue culture utilizing Luria-Bertani (LB) media, at a concentration of 12.0 microg/mL and inhibited the growth of E. coli (XL-1 blue) from 15% to 20% within the initial sixteen hours.
TL;DR: In this paper, the 1,3-dipolar cycloadditions of bis(diisopropylamino)phosphinodiazomethane, 10, to chiral electron-deficient olefins have been investigated for the first time.
Abstract: The 1,3-dipolar cycloadditions of bis(diisopropylamino)phosphinodiazomethane, 10, to chiral electron-deficient olefins have been investigated for the first time. The results have been compared with those corresponding to the reactions of diazomethane and the same or similar substrates. The experimental observations have been rationalized by DFT theoretical calculations. Diazomethane has been shown to be more reactive than 10 in all cases. The dipolarophiles include compounds synthesized from d -glyceraldehyde acetonide and (−)-verbenone. The latter compounds, bearing a gem-dimethylcyclobutane moiety, are less reactive than those derived from d -glyceraldehyde bearing a dioxolane ring. The influence of the Z/E geometry of the double bond on the reactivity and the π-facial diastereoselectivity has been investigated. Thus, in the reactions of diazomethane, the diastereoselectivity is not dependent on the Z/E stereochemistry but the reactivity is lower for (E)-cyclobutyl derivatives than for their Z isomers. In the reactions between 10 and the glyceraldehyde derivatives, the E isomers are less reactive than the Z ones and afford adducts with poor facial diastereoselectivity due to unfavorable interactions between the reactants in the corresponding transition states.
TL;DR: In this article, a cycloadduct of various 1,3-dipoles to methyl (S)-1-tert-butoxy-carbonyl-3-cyanomethyl-1,2-dihydro-2-oxo-5H-pyrrole-5-carboxylate was studied.
TL;DR: A range of α-amino acid-derived cyclisation precursors were synthesised from suitably protected αamino esters, via a Dibal-H/Wittig/catalytic hydrogenation strategy and each of these was subjected to alkylidene carbene-forming conditions (lithio(trimethylsilyl)diazomethane, THF) as discussed by the authors.
Patent•
20 Sep 2002
TL;DR: In this paper, a sulfonyl diazomethane shown by general formula (1) [wherein, R is H, a 1-4C straight-chain, branched or cyclic (substituted) alkyl or alkoxy] is provided.
Abstract: PROBLEM TO BE SOLVED: To afford high resolution with good pattern profile design after development and therefore suitable for fine processing. SOLUTION: A sulfonyl diazomethane shown by general formula (1) [wherein, R is H, a 1-4C straight-chain, branched or cyclic (substituted) alkyl or alkoxy; G is SO 2 or CO; R 3 is a 1-10C straight-chain, branched or cyclic (substituted) alkyl or 6-14C (substituted) aryl; p is 1 or 2; q is 0 or 1, (p+q) is 2, n is 0 or 1; m is an integer of 3-11; and k is an integer of 0-4] is provided. COPYRIGHT: (C)2003,JPO
TL;DR: In this article, the 1,3-Dipolar cycloaddition of diazomethane to (1,1-difluoroallyl)phosphonates was examined to give pyrazolines functionalized by a diethoxyphosphoryldifluoromethylene unit.
Abstract: 1,3-Dipolar cycloaddition of diazomethane to (1,1-difluoroallyl)phosphonates was examined to give pyrazolines functionalized by a diethoxyphosphoryldifluoromethylene unit. The pyrazolines were transformed to the cyclopropane derivatives possessing a diethoxyphosphoryldifluoromethylene functionality by photolysis.
TL;DR: By treating 4-aryl-2,4-dioxobutanoic acids or their alkyl esters with diazomethane alkyls 4-R-3-aroyl, 4-methoxy-4-oxo-2-butenoates, and 1-R 3-Aroyl-4methoxoxycarbonyl 4,5-dihydropyrazoles were prepared as mentioned in this paper.
Abstract: By treating 4-aryl-2,4-dioxobutanoic acids or their alkyl esters with diazomethane alkyl 4-aryl-2-methoxy-4-oxo-2-butenoates and 1-R-3-aroyl-4-methoxy-4-methoxycarbonyl-4,5-dihydropyrazoles were prepared. O-Alkyl derivatives and substituted pyrazoles were also obtained by reaction of 4-aryl-2,4-oxo-butanoic acids aryl amides with diazomethane and diazoethane.
TL;DR: In this article, the 1,3-dipolar cycloaddition reactions of benzyl azide, diazomethane, a nitrile oxide and a Nitrile imine to α-methylidene-γ-lactone dipolarophile was effectively controlled by a bulky γ-substituent, 4-methyl-2,6,7-trioxabicyclo[2.2]octan-1-yl in γ position of the dipolarophore.
Abstract: Diastereoselectivity of 1,3-dipolar cycloaddition reactions of benzyl azide, diazomethane, a nitrile oxide and a nitrile imine to α-methylidene-γ-lactone dipolarophile was effectively controlled by a bulky γ-substituent, 4-methyl-2,6,7-trioxabicyclo[2.2.2]octan-1-yl in γ-position of the dipolarophile. The dipoles added from the less hindered face of the double bond with an excellent selectivity. Enantiomerically pure dipolarophile was prepared from the easily available ( S )-5-oxotetrahydrohydrofuran-2-carboxylic acid.
TL;DR: In this article, the preparation of 2',3'-methano-carbocyclic analogues of adenosine was reported, and the addition of diazomethane to N-substituted 2-azabicylo[2.2.1]-hept-5-en-3-one (ABH) provided cyclopropane-fused ABH.
Abstract: The preparation of 2',3'-methano-carbocyclic analogues of adenosine is reported. The addition of diazomethane to N-substituted 2-azabicylo[2.2.1]-hept-5-en-3-one (ABH) (1) provided cyclopropane-fused ABH (3), which was converted to 2',3'-methano carbocyclic nucleosides (8).
TL;DR: In this paper, the tricyclic adducts 7 and 9 in a 1:1 ratio were obtained by internal aldol cyclization to obtain the bicyclodione intermediates 6 and 8.
TL;DR: In this paper, the cycloaddition and cyclocondensation reactions of diazomethane and hydrazine hydrate with bis olefinic systems were reported.
Abstract: Mono and bis pyrazolines were prepared by the cycloaddition and cyclocondensation reactions of diazomethane and hydrazine hydrate with bis olefinic systems. Introduction : The chemistry of heterocyclic compounds particularly nitrogen containing five membered heterocycles is one of the well attended branches of chemistry due to their broad spectrum of physiological action and diverse physicochemical properties.\"\"' Amongst them pyrazole and its derivatives have acquired importance due to their wide spectrum of biological properties/ ' Various methods were developed for their synthesis over the years, of which the cycloaddition of diazomethane and cyclocondensation of hydrazine hydrate with Micheal acceptors have gained importance. In our earlier communications, the reactivity of bifunctional olefins with diazomethane and hydrazine hydrate was reported.· Results and Discussion : The synthetic scheme involves the treatment of l,5-diaryl-3-methyl-l,4-pentadien-3-one (1) with two-fold excess of diazomethane. After work-up the reaction mixture indicated the formation of two adducts in TLC and they were separated by column chromatography. They were identified as 4-aryl-3-(3'-aryl-2'-methyl-2-propenone)-2-pyrazoline (2) as major (60-73%) and 4-aryl-5-methyl5-(3'-aryl-2'-propcnone)-2-pyrazolinc (3) as minor (12-25%) products by their 'l l NMR spectra (Scheme and Tables I & 2). The 2 showed AMX splitting pattern for methine and methylene protons of pyrazoline ring. The ΙΙΛ displayed a double doublet at 4.47-4.51 (./ΛΜ = 12.60-12.62, ,/ΛΧ = 5.42-5.55 II/.). IIM at 3.64-3.68 (./MX 10.01-10.05 II/.) and l l x al 3.52-3.5X. The ./ values Vol. 8. No. 1, 2002 Reactivity of bisolefmic systems with diazomethane and hydrazine hydrate-part III
01 Jan 2002
TL;DR: In this article, the use of acid methanol esterification followed by gas chromatography with electron capture detection (ECD) was applied for the determination of the nine haloacetic acids in water.
Abstract: Acidic methanol esterification followed bygas chromatography(GC) with electron capture detection (ECD) was applied for the determination of the nine haloacetic acids in water. The main advantage of this method is the use of acidic methanol as the derivatization agent instead of the hazardous diazomethane. The recoveries, estimated at concentrations ranging from 0.5 to 30mg/l, are high for eight of the nine haloacetic acids, with the onlyexception being monochloroacetic acid. However, problems with this compound have been reported with diazomethane derivatization methods as well. The detection limits of the method range from 0.01 to 0.2mg/l. r 2002 Elsevier Science Ltd. All rights reserved.
TL;DR: In this article, Semi-empirical molecular orbital calculations (AM1) were carried out for compound 12 which gave an idea about its stable conformation, and also supported the existence of the anomeric effect.
Abstract: Reaction of tri-O-acetyl-D-glucal (1) with cyclohexanol (2) using Ferrier's method provided the unsaturated cyclohexyl glucoside 3, which furnished the title compound 12 in a sequence involving hydrolysis, selective tritylation of oxygen at C-6, allylic oxidation with MnO2 and 1,3-dipolar cycloaddition with diazomethane. Starting from 6, product 17 was obtained in four steps. Semi-empirical molecular orbital calculations (AM1) were carried out for compound 12 which gave an idea about its stable conformation, and also supported the existence of the anomeric effect. Attempts to open the pyrazoline ring in 12 and 17 failed. Partial negative charge at C-3 was responsible for the lack of reactivity of 12 towards reduction of C=N bond.