Showing papers on "Diazomethane published in 2007"
TL;DR: The SF5 group increases density remarkably and as a result enhances the detonation performance of the energetic materials relative to the CF3 group.
162 citations
141 citations
139 citations
TL;DR: In this article, the diazomethane-mediated cyclopropanation of cyclohexenone using Pd(OAc)2 and different sources of pd(0) species as precatalysts has been studied.
34 citations
TL;DR: Crystal structures of photoinduced triplet diphenylcarbenes (DPCs) of 1, 2, and 4 were determined and remarkable differences between their structural information obtained in the crystalline state and that previously obtained spectroscopically in a glass matrix are found.
Abstract: Crystalline-state photoreactions of the following diphenyldiazomethanes were investigated by in situ X-ray crystallography, spectroscopy, and theoretical calculations: bis(2,4,6-trichlorophenyl)diazomethane (1-N2), bis(2,4,6-tribromophenyl)diazomethane (2-N2), bis(2,6-dibromo-4-methylphenyl)diazomethane (3-N2), bis(2,6-dibromo-4-tert-butylphenyl)diazomethane (4-N2), (2,4,6-tribromophenyl)-(2,6-dimethyl-4-tert-butylphenyl)diazomethane (5-N2), bis(4-bromophenyl)diazomethane(6-N2), and diazofluorene (7-N2). Crystal structures of photoinduced triplet diphenylcarbenes (DPCs) of 1, 2, and 4 were determined. We found remarkable differences between their structural information obtained in the crystalline state and that previously obtained spectroscopically in a glass matrix. Although the triplet DPCs of 1, 2, and 4 have significantly different stabilities in solution, only subtle differences in their structural parameters, except for their C(:)-Ar bond lengths, are observed. It is noteworthy that the average bond length of C(:)-Ar for 4 (1.374 A) is considerably shorter than those for (3)1 and (3)2 (1.430 and 1.428 A, respectively), provided that the two C(:)-Ar bonds being compared were chemically equivalent. The most likely explanations for the small and large differences in bond lengths in 1, 2, and 4 may be derived from the packing effect. The packing patterns of 1 and 2 are identical, but that of 4 is totally different from those of 1 and 2. Moreover, these results are interpreted as indicating that triplet DPCs undergo relaxation upon softening of the environments. Theoretical calculations indicate that the potential energy surface of triplet DPCs in terms of the carbene angle is extremely flat and changes in the angles have little effect on the energies. Triplet DPCs with a sterically congested carbene center are trapped in a structure dictated by the precursor structure in a rigid matrix, even if this is not the thermodynamically most stable geometry, but undergo geometrical relaxation upon softening the matrix to relieve steric compression. ESR studies indicate that the interplanar angles are more flexible than the bond angles.
31 citations
TL;DR: In this contribution, Potential Energy Surfaces are constructed at the reliable G2M level of theory and used to evaluate thermal rate constants by Transition State Theory and compelling theoretical and experimental evidence is presented that an oxadiazole intermediate not only can undergo a hydrogen shift, but eventually also a methyl- or even an alkyl-shift.
Abstract: The thermal reaction of olefins with nitrous oxide was recently put forward as a promising synthetic ketone source. The 1,3-dipolar cycloaddition of N2O to the CC double bond, forming a 4,5-dihydro-[1,2,3]oxadiazole intermediate, was predicted to be the first elementary reaction step. This oxadiazole can subsequently decompose to the desired carbonyl product and N2via a hydrogen shift. In this contribution, Potential Energy Surfaces are constructed at the reliable G2M level of theory and used to evaluate thermal rate constants by Transition State Theory. Compelling theoretical and experimental evidence is presented that an oxadiazole intermediate not only can undergo a hydrogen shift, but eventually also a methyl- or even an alkyl-shift. Special emphasis is also given on a hitherto neglected decomposition of the oxadiazole via a concerted C–C and N–O cleavage. For some substrates, such as internal olefins, this diazo route is negligibly slow, compared to the ketone path, leaving no marks on the selectivity. For cyclopentene the diazo cleavage was however found to be nearly as fast as the desired ketone route. However, the diazo compound, viz. 5-diazopentanal, reconstitutes the oxadiazole much faster upon ring-closure than it is converted to side-products. Therefore, a pre-equilibrium between the diazoalkanal and the oxadiazole is established, explaining the high ketone yield. On the other hand, for primary alkenes, such a concerted C–C and N–O cleavage to diazomethane is identified as an important side reaction, producing aldehydes with the loss of one C-atom. For these substrates, the bimolecular back-reaction of the Cn−1 aldehyde and diazomethane is too slow to sustain an equilibrium with the oxadiazole; diazomethane rather reacts with the substrate to form cyclopropane derivatives. The overall selectivity is thus determined by a combination of H-, methyl- or alkyl-shift, and the eventual impact of a diazo cleavage in the oxadiazole intermediate.
30 citations
TL;DR: The improved ion-pair solid-phase extraction (IP-SPE) method was applied to the analysis of aqueous samples given in one of the official proficiency tests conducted by the Organization for the Prohibition of Chemical Weapons and all the spiked chemicals were identified as methyl esters.
26 citations
TL;DR: In this paper, the key intermediates N-methyl-N-nosyl-α-aminoacyldiazomethanes are prepared in only one step, by a simple treatment of the corresponding Nnosylα-α-, aminoacyl chlorides with diazomethan, taking advantage of the use of the nosyl group.
Abstract: N-Methyl-β3-amino acids are important building blocks in the synthesis of biologically active molecules. A very simple and efficient approach to transform natural α-amino acids into their corresponding N-methyl-β3-amino acids is here presented. In the method, the key intermediates N-methyl-N-nosyl-α-aminoacyldiazomethanes are prepared in only one step, by a simple treatment of the corresponding N-nosyl-α-aminoacyl chlorides with diazomethane. The synthetic route takes advantage from the use of the nosyl group. This N-masking moiety activates the NH function, and the N-methylation can directly occur during the acylation step of diazomethane, rendering useless a second step that instead is shown to be necessary in all the classical procedures already reported for the preparation of N-methyl-β3-amino acids. The Wolff rearrangement of N-methyl-N-nosyl-α-aminoacyldiazomethanes provides the corresponding N-methyl-N-nosyl-β3-amino acids with total retention of the chiral configuration of the starting α-amino aci...
25 citations
TL;DR: In this paper, a simple solid-phase synthesis of N-nosyl-N-methyl-α-amino acids and N-Fmoc-n-methyl α amino acids is presented.
Abstract: We report here a convenient and simple solid-phase synthesis of N-nosyl-N-methyl-α-amino acids and N-Fmoc-N-methyl-α-amino acids, important building blocks for the synthesis of conformationally restricted and protease-resistant natural peptides and peptide analogues. The methodology involves the use of 2-chlorotrityl chloride resin to temporarily protect the carboxylic group of α-amino acids and of diazomethane as the reagent to methylate the sulfonamidic function. The approach developed is particularly efficient also with α-amino acids bearing appropriately protected functionalized side chains.
21 citations
TL;DR: In this paper, the 19F and 13C-NMR spectra allow the structural assignment of two diastereoisomers, 9A and 9B, and the open-chain zwitterion 10, assumed as intermediate, adds the second molecule of (E)-BTE.
Abstract: Di(tert-butyl)diazomethane (4) is a nucleophilic 1,3-dipole with strong steric hindrance at one terminus. In its reaction with 2,3-bis(trifluoromethyl)fumaronitrile ((E)-BTE), a highly electrophilic tetra-acceptor-substituted ethene, an imino-substituted cyclopentene 9 is formed as a 1 : 2 product. The open-chain zwitterion 10, assumed as intermediate, adds the second molecule of (E)-BTE. The 19F- and 13C-NMR spectra allow the structural assignment of two diastereoisomers, 9A and 9B. The zwitterion 10 can also be intercepted by dimethyl 2,3-dicyanofumarate (11) and furnishes diastereoisomeric cyclopentenes 12A and 12B; an X-ray-analysis of 12B confirms the ‘mixed’ 1 : 1 : 1 product. Competing is an (E)-BTE-catalyzed decomposition of 4 to give 2,3,4,4-tetramethylpent-1-ene (7)+N2; the reaction of (E)-BTE with a trace of water appears to be responsible for the chain initiation. The H2SO4-catalyzed decomposition of diazoalkane 4, indeed, produced the alkene 7 in high yield. The attack on the hindered diazoalkane 4 by 11 is slower than that by (E)-BTE; the zwitterionic intermediate 21 undergoes cyclization and furnishes the tetrasubstituted furan 22. In fumaronitrile, electrophilicity and steric demand are diminished, and a 1,3-cycloaddition produces the 4,5-dihydro-1H-pyrazole derivative 25. The reaction of 4 with dimethyl acetylenedicarboxylate leads to pyrazole 29+isobutene.
19 citations
TL;DR: A series of regioisomeric ketene-O,O-dialkyl acetals were prepared from ambident β-dicarbonylfuroindoles by trapping the enol tautomers of esters and lactones with diazomethane.
TL;DR: In this article, a simple method for the synthesis of 1-arylcyclopropylphosphonates was proposed, which involves treatment of 1arylethenylphophosphonic acids or their esters with diazomethane followed by thermolysis of intermediate 3-aryl-4,5-dihydro-3H-pyrazol-3-ylph phosphonates.
Abstract: A simple method for the synthesis of 1-arylcyclopropylphosphonates was proposed. The method involves treatment of 1-arylethenylphosphonic acids or their esters with diazomethane followed by thermolysis of intermediate 3-aryl-4,5-dihydro-3H-pyrazol-3-ylphosphonates.
TL;DR: The reaction of naphthoquinone-oximes with diazomethane yields directly, in one step, the oxazoles (5) and (6), respectively.
Abstract: The reaction of naphthoquinone-oximes (3) and (4) with diazomethane yields directly, in one step, the oxazoles (5) and (6), respectively.
TL;DR: The preparation of [ 11C]chloroform by direct chlorination of [11C]methane using gaseous chlorine by variation of temperature and reaction time (inert gas flow) without catalyst support for the online production of [12C]diazomethane in a flow-through synthesis apparatus is described in this work.
TL;DR: Ferrocenyl pyrazolines have been prepared by the reaction of ferroceneyl chalcones with diazomethane and/or substituted benzenesulphonyl hydrazides as discussed by the authors.
Abstract: Ferrocenyl pyrazolines have been prepared by the reaction of ferrocenyl chalcones with diazomethane and/or substituted benzenesulphonyl hydrazides. A Michael reaction on ferrocenyl chalcones using phenyl benzyl ketone and/or thiophenol yielded the corresponding ferrocenyl pentan-1,5-diones and ferrocenyl-β-ketosulphides, respectively.
TL;DR: In this article, 3+2 dipolar cycloaddition reactions of propargyl, allyl and cyano substituted 2,3-benzodiazepines with in situ generated nitrile oxides and diazomethane were reported.
TL;DR: In this paper, the cycloadditions of methyl diazoacetate to 2,3-bis(trifluoromethyl)fumaronitrile ((E)-BTE) and 2, 3-bis (triffluoromethsyl)maleonitrile((Z)-B TE) furnish the 4,5-dihydro-1H-pyrazoles 13.
Abstract: The cycloadditions of methyl diazoacetate to 2,3-bis(trifluoromethyl)fumaronitrile ((E)-BTE) and 2,3-bis(trifluoromethyl)maleonitrile ((Z)-BTE) furnish the 4,5-dihydro-1H-pyrazoles 13. The retention of dipolarophile configuration proceeds for (E)-BTE with > 99.93% and for (Z)-BTE with > 99.8% (CDCl3, 25°), suggesting concertedness. Base catalysis (1,4-diazabicyclo[2.2.2]octane (DABCO), proton sponge) converts the cycloadducts, trans-13 and cis-13, to a 94 : 6 equilibrium mixture (CDCl3, r.t.); the first step is N-deprotonation, since reaction with methyl fluorosulfonate affords the 4,5-dihydro-1-methyl-1H-pyrazoles. Competing with the cis/trans isomerization of 13 is the formation of a bis(dehydrofluoro) dimer (two diastereoisomers), the structure of which was elucidated by IR, 19F-NMR, and 13C-NMR spectroscopy. The reaction slows when DABCO is bound by HF, but F− as base keeps the conversion to 22 going and binds HF. The diazo group in 22 suggests a common intermediate for cis/trans isomerization of 13 and conversion to 22: reversible ring opening of N-deprotonated 13 provides 18, a derivative of methyl diazoacetate with a carbanionic substituent. Mechanistic comparison with the reaction of diazomethane and dimethyl 2,3-dicyanofumarate, a related tetra-acceptor-ethylene, brings to light unanticipated divergencies.
TL;DR: In this paper, a short and efficient route to δ-lactone-fused cyclopentanoids starting from easily accessible Diels-Alder adducts between homoallylic alcohol acetates and 1,2,3,4-tetrachloro-5,5-dimethoxycyclopenta-1,3-diene is reported.
Abstract: A short and efficient route to δ-lactone-fused cyclopentanoids starting from the easily accessible Diels-Alder adducts between homoallylic alcohol acetates and 1,2,3,4-tetrachloro-5,5-dimethoxycyclopenta-1,3-diene is reported. Since homoallyl alcohols were derived from the corresponding aldehydes RCHO (R = alkyl, aryl) through allyl metal addition, the methodology is broad in scope with regard to the choice of R group. The initially formed 1:1 diastereomeric mixture of adducts were subjected to ruthenium-catalyzed oxidation followed by acid-mediated hydrolysis of the acetate groups to obtain the hemiacetals 6A- E. Alkaline H 2 O 2 -mediated cleavage of the hemiacetals led, after esterification with diazomethane, to a chromatographically separable diastereomeric mixture of 7 and 8 in high overall yield (54-68%).
TL;DR: Diazomethane was reacted with nitro-substituted anils of thiophenealdehyde and/or isatin and with some unsymmetric azines as mentioned in this paper.
Abstract: Diazomethane was reacted with nitro-substituted anils of thiophenealdehyde and/or isatin and with some unsymmetric azines. 1,2,3-Triazolines were obtained in all cases. Product constitution is discussed. Some of these were found to inhibit the development of a range of Gram-positive and Gram-negative bacteria.
Patent•
22 Feb 2007
TL;DR: In this article, a low molecular weight compound obtained by substituting one hydrogen atom or more of a compound comprising an amino group where the hydrogen atom is combined with a nitrogen atom by a t-butoxy carbonyl group, is selected from among groups of the compound of formula (1), 1-adamanthylamine, nitrogen-containing heterocyclic compound, or the like.
Abstract: PROBLEM TO BE SOLVED: To provide a positive radiation-sensitive resin composition that is superior in sensitivity and resolution, small in an optical proximity effect, and ensures a sufficient focus margin for an isolated line pattern SOLUTION: The radiation-sensitive resin composition contains (A) a low molecular weight compound obtained by substituting one hydrogen atom or more of a compound comprising an amino group where the hydrogen atom is combined with a nitrogen atom by a t-butoxy carbonyl group, (B) a radiation-sensitive acid generator, and (C) an acid dissociation group-containing resin The compound having the amino group where the hydrogen atom is combined with the nitrogen atom is selected from among groups of a compound of formula (1), 1-adamanthylamine, nitrogen-containing heterocyclic compound, or the like The (B) constituent is selected from among a bis(cyclohexane sulfonyl)diazomethane, N-(triflouromethanesulfonyloxy)bicyclo[221]hepto-5-ene-2, 3-dicarboximide, or the like In the formula, R 1 and R 2 represent the hydrogen atom, alkyl group, or the like COPYRIGHT: (C)2009,JPO&INPIT
TL;DR: The [3+2]-cycloaddition of (trimethylsilyl)diazomethane (7) with 9H-fluorene-9thione (1) at -60°C yields the spirocyclic 2,5-dihydro-5-trimmethylsilylsilyl-1,3,4-thiadiazole 10, which eliminates nitrogen at room temperature to give the 1,4dithiane derivative 13 by dimerization of the intermediate fluorenethione (tr
Abstract: The [3+2]-cycloaddition of (trimethylsilyl)diazomethane (7) with 9H-fluorene-9-thione (1) at –60°C yields the spirocyclic 2,5-dihydro-5-trimethylsilyl-1,3,4-thiadiazole 10, which eliminates nitrogen at room temperature to give the 1,4-dithiane derivative 13 by dimerization of the intermediate fluorenethione (trimethylsilyl)methanide (11). This thiocarbonyl ylide can be trapped by 1 to give the 2-trimethylsilyl-1,3-dithiolane 14 via [3+2]-cycloaddition. Furthermore, the 1,3-dipole 11 undergoes successfully [3+2]-cycloadditions with the C=S group of the phosphonyldithioformate 15 as well as with the C=C dipolarophiles maleic anhydride (18a) and N-(cyclohexyl)maleimide (18b). The structures of 13 and 14 have been established by X-ray crystallography.
TL;DR: The structure of the latter has been demonstrated by XRD for the hydrochloride of 3-methoxy-2-oxo-3-(2-phenyl-2oxoethyl)-2,3-dihydroimidazo[1,2-a]pyridine.
Abstract: Reactions between 2-pyridylamides of Z-4-aryl-2-hydroxy-4-oxobut-2-enoic acids with diazomethane have been used to synthesize 3-(2-aryl-2-oxoethyl)-3-methoxy-2-oxo-2,3-dihydroimidazo[1,2-a]pyridines, which form hydrochlorides with hydrochloric acid. The structure of the latter has been demonstrated by XRD for the hydrochloride of 3-methoxy-2-oxo-3-(2-phenyl-2-oxoethyl)-2,3-dihydroimidazo[1,2-a]pyridine.
Patent•
01 Oct 2007
TL;DR: In this paper, the authors proposed a method to decompose a diazomethane source to another vessel containing a solution of reactant, which is also water-soluble.
Abstract: The present invention relates to compounds useful in the preparation of diazoalkanes in general (such as diazomethane, diazoethane, diazopropane, diazobutane and homologues) and to diazomethane (CH2=N=N) in particular. The compounds chosen as the diazomethane source according to the invention also have the advantage of being water soluble. They are capable of being decomposed to diazomethane or another diazoalkane (which is allowed to bubble out of the vessel to another vessel containing a solution of reactant) and are converted to by-products that are also water-soluble.
05 Jan 2007
TL;DR: In this article, a short and efficient route to δ-lactone-fused cyclopentanoids starting from easily accessible Diels-Alder adducts between homoallylic alcohol acetates and 1,2,3,4-tetrachloro-5,5-dimethoxycyclopenta-1,3-diene is reported.
Abstract: A short and efficient route to δ-lactone-fused cyclopentanoids starting from the easily accessible Diels-Alder adducts between homoallylic alcohol acetates and 1,2,3,4-tetrachloro-5,5-dimethoxycyclopenta-1,3-diene is reported. Since homoallyl alcohols were derived from the corresponding aldehydes RCHO (R = alkyl, aryl) through allyl metal addition, the methodology is broad in scope with regard to the choice of R group. The initially formed 1:1 diastereomeric mixture of adducts were subjected to ruthenium-catalyzed oxidation followed by acid-mediated hydrolysis of the acetate groups to obtain the hemiacetals 6A- E. Alkaline H 2 O 2 -mediated cleavage of the hemiacetals led, after esterification with diazomethane, to a chromatographically separable diastereomeric mixture of 7 and 8 in high overall yield (54-68%).
Dissertation•
01 Jan 2007
TL;DR: In this article, three different derivatisation procedures were evaluated for their general applicability to systematic toxicological analysis (STA) involving acylation with pentafluoropropionyl anhydride (PFPA), silylation with tertiary-butyldimethylsilyl-trifluoroacetamide (MTBSTFA), and a novel methylating agent (TMS-diazomethane) used as a chromatographic derivatization reagent.
Abstract: Three different derivatisation procedures were evaluated for their general applicability to systematic toxicological analysis (STA) involving (a) acylation with pentafluoropropionyl anhydride (PFPA) and pentafluoropropanol (PFP-OH), (b) acylation/esterification (methylation) with pentafluoropropionyl anhydride (PFPA) and a novel methylating agent trimethylsilyldiazomethane (TMS-diazomethane), used as a chromatographic derivatisation reagent for the first time in this study, and (c) silylation with tertiary-butyldimethylsilyl-trifluoroacetamide (MTBSTFA). Model compounds were selected for the evaluation process including a primary amine (amphetamine), a secondary amine (methamphetamine), alicyclic and aromatic hydroxy compounds (morphine, tetrahydrocannabinol), and carboxylic acids (benzoylecgonine, 11-nor tetrahydrocannabinol-9-carboxylic acid).
For method (a) derivatisation was successful for all of the test compounds and mass spectra were obtained for each of them. For method (b), the novel methylating agent trimethylsilyl-diazomethane was used to convert carboxylic acids into the corresponding methyl esters. This reaction was found to proceed rapidly and quantitatively at room temperature and holds potential for future use in toxicology to replace diazomethane, a hazardous and toxic material. Method (c) gave derivatives with all test compounds except the secondary amine, methamphetamine, and the alcohol, morphine. The gas chromatographic behaviour of these derivatives was good and the mass spectra had prominent ions suitable for GC-MS-SIM.
The extraction of multiple drugs from blood was evaluated using the novel polymeric SPE sorbent Strata-X. The same test compounds were used to assess the extraction step in terms of recovery and variation (within day and between days). The extracts were analysed by GC-MS-SIM using each of the three types of derivative. Recoveries of the test compounds were in the range of 50-100 percent depending on the analyte and its concentration in blood. All calibration curves were linear and had correlation coefficients higher than 0.99. Within day variations and between day variations were in the range of 2-22% relative standard deviation. Limits of detection and quantitation were measured for the model compounds and were found to be in the ranges of 0.4-7.3 ng/ml and 1.1-24.4 ng/ml respectively. The full method, combining extraction with each of the derivatisation reactions was finally evaluated for the presence of interferences with real case blood samples.
The three derivatisation procedures were evaluated using four test compounds comprising diazepam plus its three metabolites nordiazepam, temazepam and oxazepam. The hydroxylated metabolites (temazepam and oxazepam) formed derivatives readily with all three reagent mixtures but nordiazepam (secondary aromatic amine) did not react except with MTBSTFA.
Based on the work of this study it is concluded that a method is possible for STA based on a polymeric sorbent, to give a general extract, followed by a generalised derivatisation procedure such as acylation, with PFPA/PFP-OH prior to GC-MS.