Synthesis of benzoxazoles from imino esters I. 2-Alkyl(aryl)-substituted benzoxazoles

It is found that condensation of esters of iminocarboxylic and iminoperfluorocarboxylic acids with o-aminophenol is a convenient general method for preparing 2-alkyl, 2-perfluoroalkyl, and 2-aryl substituted benzoxazoles. Hydrochlorides of esters of iminocarboxylic acids react smoothly with o-aminophenol even at room temperature. Condensation of esters of iminoperfluorocarboxylic acids, whose hydrochlorides are unstable, is suitably carried out in the presence of an equimolecular quantity of the corresponding perfluorocarboxylic acid. 2-Alkyl(aryl) substituted benzoxazoles can also be obtained by heating o-aminophenol with esters of iminocarboxylic acids in the form of free bases. Esters of iminoperfluorocarboxylic acids also react similarly. Under similar conditions diesters of bisiminocarboxylic and bisiminoperfluorocarboxylic acids and o-aminophenol giveα, ω-di(benzoxazolyl-2) alkanes, andα, ω-di(benzoxazolyl-2) perfluoroalkanes respectively.     

Nouvelle méthode de synthèse d’acides et d’esters arylboroniques par électroréduction de dérivés aromatiques halogénés en présence d’agents boratants

Novel synthesis of arylboronic acids and esters by electroreduction of aromatic halides in the presence of borating agents. A novel strategy for the one-step synthesis of arylboronic acids and esters by an electrochemical coupling reaction is described. It is based on the reductive coupling between the aromatic halides and a borating agent (trialkyl borate or pinacolborane). The reactions are carried out in DMF or THF with the use of sacrificial magnesium or aluminium anodes in a single-compartment cell. Arylboronic acids and esters are obtained with moderate-to-good isolated yields. To cite this article: C. Laza, E. Duñach, C. R. Chimie 6 (2003).     

Synthesis and biological evaluations of some Schiff-base esters of ferrocenyl aniline and simple aniline

The synthesis and biological studies of some long chain esters containing Schiff bases and their ferrocenyl analogues were carried out. The 4-amino ferrocene was prepared by the reported method. Long chain esters were synthesized by the condensation of different aliphatic acids with the corresponding aldehyde. The esters were then reacted with aniline as well as with 4-aminophenyl ferrocene to give corresponding Schiff bases. All the synthesized compounds were analyzed by elemental, FTIR and proton NMR studies, were also investigated for a range of biological activities. Determined by crown gall tumor inhibition assay. Antioxidant and DNA protective activities were determined by DPPH free radical scavenging assay and OH radical induced oxidative DNA damage assay, respectively. Among all test compounds, o-hydroxy-p-n-octadecanoyloxy-benzylidine-p-ferrocenyl aniline (FA2.1: a ferrocene containing Schiff base) showed highest antitumor, DPPH free radical scavenging and DNA protective activities.     

Thermolysis of the esters of substituted 3,7-triazabicydo[3.3.0]oct-3-ene-4-carboxylic acids

Heating to 190–200‡C of the esters of substituted 2,3,7-triazabicyclo[3.3.0]oct-3-ene-4-carboxylic acids afforded esters of 3-azabicyclo[3.1.0]hexane-6-carboxylic acids as a mixture of exo and endo isomers. The reaction carried out in chlorobenzene at 130‡C in the presence of copper stearate yielded only exo isomers. The study was carried out under financial support of the Russian Ministry of Education (grant no. 97-0-9.4-118).     

Synthesis of Isothiocyanates Using DMT/NMM/TsO− as a New Desulfurization Reagent

Thirty-three alkyl and aryl isothiocyanates, as well as isothiocyanate derivatives from esters of coded amino acids and from esters of unnatural amino acids (6-aminocaproic, 4-(aminomethyl)benzoic, and tranexamic acids), were synthesized with satisfactory or very good yields (25–97%). Synthesis was performed in a “one-pot”, two-step procedure, in the presence of organic base (Et₃N, DBU or NMM), and carbon disulfide via dithiocarbamates, with 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium toluene-4-sulfonate (DMT/NMM/TsO⁻) as a desulfurization reagent. For the synthesis of aliphatic and aromatic isothiocyanates, reactions were carried out in a microwave reactor, and selected alkyl isothiocyanates were also synthesized in aqueous medium with high yields (72–96%). Isothiocyanate derivatives of L- and D-amino acid methyl esters were synthesized, under conditions without microwave radiation assistance, with low racemization (er 99 > 1), and their absolute configuration was confirmed by circular dichroism. Isothiocyanate derivatives of natural and unnatural amino acids were evaluated for antibacterial activity on E. coli and S. aureus bacterial strains, where the most active was ITC 9e.     

A synthesis of optically active α-quaternary α-amino acids and esters by assembling three components, ketones, (R)-chloromethyl p-tolyl sulfoxide, and sodium azide, via sulfinyloxiranes

Treatment of lithium α-sulfinyl carbanion of chloromethyl p-tolyl sulfoxides with ketones at low temperature afforded adducts in almost quantitative yields, which were exposed to t-BuOK to give sulfinyloxiranes in high yields. The sulfinyloxirane was reacted with benzylamine to give α-amino aldehyde, which was oxidized with iodine in methanol to afford α-amino carboxylic ester in moderate yield. The sulfinyloxiranes were treated with sodium azide to afford α-azido aldehydes in good yields. Oxidation with NaClO₂ followed by catalytic hydrogenation of the azido group of the α-azido aldehydes gave α-quaternary α-amino acids in good overall yields. The oxidation of the azido aldehydes with iodine in methanol in the presence of KOH followed by the catalytic hydrogenation resulted in α-quaternary α-amino acid methyl esters in good yields. When these reactions were carried out starting from unsymmetrical ketones and optically pure (R)-chloromethyl p-tolyl sulfoxide, a new method for a synthesis of optically active α-quaternary α-amino acids and esters in good overall yields was realized.     

Improved Cs2CO3 Promoted O-Alkylation of Acids

Cesium carbonate mediated O-alkylation of carboxylic acids was efficiently carried out under mild in situ conditions to give the corresponding esters exclusively. Chiral templates including α-hydroxy and α-alkoxy acids were also converted to their corresponding esters with no observed racemization.     

Efficient esterification of carboxylic acids and phosphonic acids with trialkyl orthoacetate in ionic liquid

An operationally simple, inexpensive, efficient, and environmentally friendly esterification of various carboxylic acids, phosphonic acids, and phosphinic acids with triethyl orthoacetate or trimethyl orthoacetate under neutral conditions in a typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate, was successfully carried out to provide the corresponding ethyl esters or methyl esters in high yields.     

A novel method for asymmetric synthesis of both enantiomers of α-substituted carboxylic acid derivatives from optically active 1-chlorovinyl p-tolyl sulfoxides and lithium ester enolates with 1,4-chiral induction from the sulfur chiral center

Treatment of optically active 1-chlorovinyl p-tolyl sulfoxides, which were synthesized from symmetrical ketones and (R)-(−)-chloromethyl p-tolyl sulfoxide in three steps, with lithium enolate of carboxylic acid tert-butyl esters gave optically active adducts having a substituent at the α-position with high 1,4-chiral induction from the sulfur chiral center in high yields. The adducts were converted to optically active esters and carboxylic acids having a chiral center at the α-position. When this addition reaction was carried out with the ester enolate generated from excess carboxylic acid tert-butyl ester with LDA in the presence of HMPA, the diastereomer of the adduct was obtained. By using the two reaction conditions for the generation of the ester enolates, a new method for asymmetric synthesis of both enantiomers of carboxylic acid derivatives having a substituent at the α-position from the one chiral source, (R)-(−)-chloromethyl p-tolyl sulfoxide, was realized.     

Diastereoselective addition of silyl metals to γ-alkoxy substituted α,β-unsaturated esters

Dimethylphenylsilyllithium adds to Z-γ-alkoxy-α,β-unsaturated esters to produce almost exclusively (i) the anti-adducts when the reaction is carried out in THF and (ii) the anti-adduct when carried out in the presence of HMPA. Poor stereocontrol is achieved with stereoisomeric E-γ-alkoxy-α,β-unsaturated esters.     

气相色谱法测定医用苯甲酸软膏中的苯甲酸与水杨酸含量

复方苯甲酸水杨酸制剂或软膏被广泛用作外用杀菌或消毒药.近年报导的测定方法主要有薄层法[1],卡尔曼滤波分光光度法[2]与气相色谱分析法[3].用气相色谱法测定苯甲酸或水杨酸等芳香酸或取代芳香酸,多将这些酸先经各种衍生反应转变为相应的酯再进行气相色谱测定[4,5].所采用的酯化衍生反应有些较为繁琐,有些反应不够完全或引入了某些衍生试剂,给分离系统或GC分离带来一些不利影响.本文提出了一种新的丁酯衍生化前处理法.用本法测定医用苯甲酸软膏中的苯甲酸与水杨酸含量,先以75%的热乙醇溶液充分溶解软膏基质,之后用冰水骤冷使基质从乙醇溶液中析出,然后将溶液中的待测酸转变为相应丁酯并选择102硅烷化白色载体涂渍5%的SE-30填充柱对各酸丁酯进行GC分离.本法定量准确,操作也较简便.     

Methylation of Aliphatic and Aromatic Carboxylic Acids with Dimethyl Carbonate under the Influence of Manganese and Iron Carbonyls

The synthesis of methyl esters has been carried out via the reaction of aliphatic and aromatic carboxylic acids with dimethyl carbonate in the presence of manganese and iron carbonyls. The optimal ratio of catalyst and reagents and other conditions for the synthesis of methyl esters of carboxylic acids with high yield have been found.     

Synthesis of N-phosphoryl amino acids using bis(9-fluorenylmethyl)phosphite

Bis(9-fluorenylmethyl)phosphite (BFMP) was found to be an effective reagent for the N-phosphorylation of various amino acid methyl esters. BFMP was prepared from N,N-diisopropyl phosphoramidous dichloride in a one-pot two-step reaction and was obtained as a crystalline solid. N-Phosphorylation of the methyl esters of seven representative amino acids with BFMP was high-yielding and generally resulted in crystalline products. Complete deprotection of both the 9-fluorenylmethylphosphosphate esters and the amino acid methyl esters was accomplished concomitantly with LiOH to give N-phosphoryl amino acids.     

The reaction of β-dicarbonyl compounds with trifluoromethylsulphenyl chloride. Part I. CF3S-substituted esters,anilides of β-keto acids,and their Schiff bases: Synthesis and stability.

The reactions of the β-keto acid derivatives with trifluoromethylsulphenyl chloride were carried out to give the α-SCF₃ substituted esters, anilides, and their Schiff bases of acetyl- and benzoylacetic acids. Ethyl esters of α-(trifluoromethylthio)acetoacetic and α-(trifluoromethylthio)benzoylacetic acids heated in dimethylsulphoxide/water solution give trifluoromethylthioacetone and ω-(trifluoromethylthio)acetophenone respectively, whereas with potassium hydroxide solution they form trifluoromethylthioacetic acid in a good yield.     

Synthesis of 11-amino-9,10-dihydro-9,10-(ethano)anthracen-12-ylphosphonic acid

Synthesis of a new representative of β-aminophosphonic acids and related esters, namely, 11-amino-9,10-dihydro-9,10-(ethano)anthracen-12-ylphosphonic acid and the respective bis(2-chloroethyl)-phosphonate was carried out.     

Method for synthesis of 1-adamantyl esters of unsaturated acids

New method for synthesis of adamantyl esters of acrylic, methacrylic, and cinnamic acids was developed. The reactions carried out under mild conditions in the absence of catalysts provide a high yield.     

Selective hydroxyl group determination by direct titration with lithium aluminum amide

The selective determination of hydroxyl groups in most complex alcohol systems by direct titration with standard lithium aluminum amide solution is described. The titration is carried out in ether solvent under nitrogen with N-phenyl-p-aminoazobenzene as reversible indicator. The accuracy is better than ± 1 % ; less than 6 min are required for a complete determination of alcohols up to triacontanol. Aldehydes, ketones, esters, amines and alkoxy groups do not interfere, but organic and inorganic acids, and water and molecular oxygen, interfere. Water and acid interferences can be corrected for after a Karl Fischer titration and neutralization reactions respectively.     

REACTION BETWEEN 2-HYDROXY ESTERS OF HYPOPHOSPHOROUS ACID AND ALCOHOLS

Abstract

A study of the reaction between esters of hypophosphorous acid and alcohols is carried out. It has been established that the 2-hydroxy esters of hypophosphorous acid react with alcohols as a result of which phosphonous acids are formed. A possible scheme of this reaction is suggested.     

3-butenyl esters as convenient protecting groups for carboxylic acids

Carboxylic acids were protected as their corresponding 3-butenyl esters. Deprotection was carried out via ozonolysis and β-elimination of the resultant 3-acyloxypropanal.     

Complexation of amino acids derivatives in water by calix[4]arene phosphonic acids

Series of the calix[4]arene phosphonic acids with various substituents at the lower rim was synthesized. Complexing properties of these receptors towards methyl esters of six amino acids strongly depended on the calix[4]arene conformation flexibility. The complex formation processes were monitored using ¹H NMR spectroscopy (deuterated phosphate buffer at pD 7.3, 22 °C) and association constant values were evaluated. Inherently mobile calix[4]arene molecule 3 occurred in cone conformation in aqueous solution turned out to be more effective in complexation of the basic amino acids methyl esters compared to the rigid 2 and flexible 4. Mixed 1:2 and 2:1 (host–guest) complexes were observed for compound 1 with all amino acids methyl esters.