Showing papers on "Diazomethane published in 2008"

Synthesis of indazoles by the [3+2] cycloaddition of diazo compounds with arynes and subsequent acyl migration.

Abstract: The [3+2] cycloaddition of a variety of diazo compounds with o-(trimethylsilyl)aryl triflates in the presence of CsF or TBAF at room temperature provides a very direct, efficient approach to a wide range of potentially biologically and pharmaceutically interesting substituted indazoles in good to excellent yields under mild reaction conditions. Simple diazomethane derivatives afford N-unsubstituted indazoles or 1-arylated indazoles, depending upon the stoichiometry of the reagents and the reaction conditions, while dicarbonyl-containing diazo compounds undergo carbonyl migration to afford 1-acyl or 1-alkoxycarbonyl indazoles selectively.

Chemical functionalization of diamond surfaces by reaction with diaryl carbenes.

Abstract: A rapid route to the chemical functionalization of hydrogen-terminated diamond surfaces deposited by chemical vapor deposition involving their reaction with substituted diaryl carbenes has been investigated. To avoid difficulties in the handling of highly reactive compounds, the carbene is generated in situ from the thermal decomposition at 400 K of a thin film of the corresponding diaryl diazomethane precursor deposited at the diamond interface. X-ray photoelectron spectroscopy (XPS) has been used to verify that surface functionalization using two starting compounds, bis(4-iodophenyl) diazomethane and bis(4-nitrophenyl) diazomethane, can be achieved using this approach in agreement with recent theoretical studies. The surface grafting density is measured to be around 1014 cm-2 in each case. The chemistry observed is found to be insensitive to the detailed properties of the diamond film and to the presence of oxygen contamination at the hydrogen-terminated diamond surface. We further demonstrate the utili...

Synthesis, Degradability, and Drug Releasing Properties of Methyl Esters of Fungal Poly(β,L‐malic acid)

Abstract: Methyl esters of microbial poly(beta,L-malic acid) for conversion degrees of 25, 50, 75, and 100% were prepared by treatment of the polyacid with diazomethane. Esterification proceeded with retention of the molecular weight of the parent polyacid and the copolymers displayed a blocky microstructure consisting of short segments of malic and methyl malate sequences. The thermal stability of the copolyesters was lower than those of the parent homopolymers and all of them were fairly crystalline with melting temperatures within the range of 170-175 degrees C. They were degraded rapidly by water, the hydrolysis rate being highly dependent on the methylation degree. Microspheres with mean-average diameters in the range of 1-20 microm were prepared from the 100% methylated product by the emulsion-evaporation solvent method. Encapsulation of erythromycin was efficiently performed in these microparticles and its releasing upon incubation in simulated physiological medium was evaluated for different drug loads. Drug delivery was observed to occur by a releasing mechanism largely determined by the hydrodegradation of the host polymer and independent of the amount of loaded drug.

Reactions of diazoalkanes with unsaturated compounds 16. Catalytic reactions of diazomethane with 2-alkenyl-1,3-oxazolidines and 2-alkenyl-1,3-oxathiolanes

Abstract: The influence of 1,3-oxazolidine and 1,3-oxathiolane fragments in substituted alkenes on the direction of their catalytic reaction with diazomethane has been investigated. The olefins bearing an oxazolidine substituent in the α- or γ-position and an oxathiolane substituent in the γ-position relative to the C=C bond react with diazomethane in the presence of Pd(acac)2 selectively resulting in cyclopropanation products. The use of Cu(OTf)2 does not result in cyclopropanation; however Cu(OTf)2 catalyzes the reaction of diazomethane with 2-(alk-1-enyl)-1,3-oxathiolanes yielding 2,3,5,6-tetrahydro-1,4-oxathiocines formed through the [2,3]-sigmatropic rearrangement of the intermediate sulfonium ylides.

A simple synthesis of 4-substituted 2-(3-hydroxy-2-oxo-1-phenethyl- propylcarbamoyl)pyrrolidine-1-carboxylic acid benzyl esters as novel cysteine protease inhibitors

Abstract: A convenient synthesis of 4-substituted 2-(3-hydroxy-2-oxo-1-phenethylpropylcarbamoyl)pyrrolidine-1-carboxylic acid benzyl esters 17 and 18 as new cysteine protease inhibitors is described. The synthetic key strategies involve the diazocarbonyl insertion reaction of N-Boc-L-homophenylalanine (1) by diazomethane, acetylation of the bromoketone 2 with sodium acetate, and condensation of acids 12, 14 with (3S)-3-amino-2-oxo-5-phenyl-pentyl acetate monohydrochloride (4) in good yield.

Synthesis, structure, and properties of N -(nitramino)phthalimide

Abstract: N-(Nitramino)phthalimide R2N-NHNO2 (R2NH is phthalimide) was synthesized by nitration of N-aminophthalimide with nitronium tetrafluoroborate. The structure of this compound was established by X-ray diffraction and confirmed by 1H, 13C, and 14N NMR spectroscopy. The methylation of this compound with diazomethane affords a mixture of N-methyl (R2N-NMeNO2) and O-methyl (R2N-N=N(O)OMe) isomers. The latter compound contains the previously unknown high-nitrogen-oxygen fragment. The thermal decomposition of N-(nitramino)phthalimide in vacuo at 80–100 °C gives 2H-3,1-benzoxazine-2,4(1H)-dione (isatoic anhydride) as the major product.

4,5-Dialkyl-substituted 3-oxo-(2H)-isothiazole 1,1-dioxides in reactions with diazomethane

Abstract: It has been established that the interaction of diazomethane with 4,5-dialkyl-substituted 3-oxo-(2H)-isothiazole 1,1-dioxides proceeds in two stages. Initially alkylation of the sulfonimide nitrogen atom and the carbonyl group oxygen atom occurs (in a ratio of ∼ 3:2), then there is a regioselective cycloaddition of diazomethane at the C=C double bond with the formation of the corresponding N-methyloxoisothiazolopyrazolines and 3-methoxyisothiazolopyrazolines.

Porphyrins and their derivatives: XXV. Reaction of 2-formyl-5,10,15,20-tetraphenylporphyrin with diazomethane

Abstract: 2-Formyl-5,10,15,20-tetraphenylporphyrin and its copper and zinc complexes react with diazomethane in a mixture chloroform-alcohol providing the corresponding 2-acetyl-and 2-acetonyl derivatives. In a pure chloroform main product of diazomethane reaction with 2-formyl-5,10,15,20-tetraphenylporphyrin is 2-acetyl-5,10,15,20-tetraphenylcyclopropa[b]chlorin.

4-aryl-2-hydroxy-4-oxobut-2-enoic acids N-(2-pyridyl)amides in reactions with diazo compounds

Abstract: Reactions of 4-aryl-2-hydroxy-4-oxobut-2-enoic acids N-(2-pyridyl)amides with diazomethane, diazoethane, diaryldiazomethanes, and diazofluorene lead to the formation of 2-alkoxy-4-aryl-4-oxobut-2-enoic acids N-(2-pyridyl)amides, 3-aroyl-5-methylpyrazole-4-carboxylic acids N-(2-pyridyl)amides, and 3-alkoxy-3-(2-aryl-2-oxoethyl)-2,3-dihydro-2-oxoimidazo[1,2-a]pyridines. The composition and structure of compounds obtained depend on the nucleophilic nature of the diazo compound and on the character of substituents in the aryl and pyridine parts of the substrate.

Formation of stable carbonyl oxide by photooxidation of (phenyl)(2-thienyl)diazomethane

Abstract: Formation of (phenyl)(2-thienyl)carbonyl oxide, which has the longest lifetime among known carbonyl oxides, has been registered by flash photolysis in acetonitrile at room temperature. It is consumed in the pseudomonomolecular reaction with the parent diazo compound.

Synthesis of Indazoles by the [3 + 2] Cycloaddition of Diazo Compounds with Arynes and Subsequent Acyl Migration.

Abstract: The [3+2] cycloaddition of a variety of diazo compounds with o-(trimethylsilyl)aryl triflates in the presence of CsF or TBAF at room temperature provides a very direct, efficient approach to a wide range of potentially biologically and pharmaceutically interesting substituted indazoles in good to excellent yields under mild reaction conditions. Simple diazomethane derivatives afford N-unsubstituted indazoles or 1-arylated indazoles, depending upon the stoichiometry of the reagents and the reaction conditions, while dicarbonyl-containing diazo compounds undergo carbonyl migration to afford 1-acyl or 1-alkoxycarbonyl indazoles selectively.

Synthesis of 1‐Arylcyclopropylphosphonates.

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.

A Mild Preparation of Substituted Indolizines and Indole from Simple Aromatic Precursors Using (Trimethylsilyl)diazomethane.

Abstract: A mild and convenient synthesis of substituted indolizines from readily available 2-(pyridin-2-yl)acetyl derivatives using (trimethylsilyl)diazomethane is described. The extension of this methodology to the synthesis of indole from 2-aminobenzaldehyde is also reported.