Subject diethyl ester

The highly substituted 5,6-dihydro-4//-l,3,4-oxadiazine (264 R = Pr") is formed as a by-product (20%) along with benzil monoxime (40%) on subjecting the O-benzylated monoxime of benzoin (PhCH(OH)C(Ph)=NOCH2Ph) to a Mitsunobu reaction (PhjP and diisopropyl azodicarboxylate) <87JOC4978>, Substitution of the diisopropyl by the diethyl ester raises the yield of oxadiazine (264 R = Et) to 50%,... 

The Storage of GB and VX neutralents from the MMD is subject to the constraints of the CWC. Some of the breakdown products (e.g., amiton [S-[2-(diethylamino)ethyl-phosphorotioic acid 0,0-diethyl ester]), are listed as Schedule 2 precursors to the manufacture of chemical agents (i.e., chemicals that could be used to remanufacture chemical agent). This means that, theoretically, the precursor chemicals in the neutralent could be reprocessed from the neutralent and used to remanufacture chemical agents. To prevent the manufacture of chemical weapons, the CWC requires that Schedule 2 precursors derived from existing... 

Addition of bromine has been the subject of a number of studies. When a neutral salt of maleic or fumaric acid (A = COO ) is brominated in water, the meso derivative is the predominant product. Bell and Pring also report that the meso product is obtained on bromination of the diethyl esters of fumaric and maleic acids. Terry and Eicheberger observed 78% meso product from disodium maleate, a cis addition product which is unexpected. The prevalent bromonium ion mechanism proposed by Roberts and Kim-ball could easily explain the trans addition as follows ... 

Mixed condensations of esters are subject to the same general restrictions as outlined for mixed aldol reactions (Section 2.1.2). One reactant must act preferentially as the acceptor and another as the nucleophile for good yields to be obtained. Combinations that work best involve one ester that cannot form an enolate but is relatively reactive as an electrophile. Esters of aromatic acids, formic acid, and oxalic acid are especially useful. Some examples of mixed ester condensations are shown in Section C of Scheme 2.14. Entries 9 and 10 show diethyl oxalate as the acceptor, and aromatic esters function as acceptors in Entries 11 and 12. 

Allylic carboxylation. Diethyl oxomalonate (1) undergoes a thermal ene reaction with mono-, di-, and trisubstituted alkenes at 145 180°. The reaction is also subject to catalysis with Lewis acids, which can lead to a different ene product. The products are a-hydroxymalonic esters. The corresponding malonic acids are converted to carboxylic acids by bisdecarboxylation with NaI04 and a trace of pyridine- or with ceric ammonium nitrate (CAN). Diethyl oxomalonate then functions as an cnophilic equivalent of C02. 

Esters of 4-oxoacids, such as ethyl levulinate, can also be cyclized in the cold by treatment with hydrogen sulfide under acid conditions. An early report (39JCS1116) described the conversion of diethyl 2-acetylsuccinate (168) to ethyl 2-methyl-5-ethoxythiophene-3-carboxylate (169), by treatment with hydrogen sulfide in alcoholic HC1 at 0 °C. The reaction was reviewed in 1977 <77PS(3)377) a large number of 4-oxoesters (170) were subjected to the hydrogen sulfide treatment, and the products were carefully isolated and characterized. 

A sample (ca. 1 g) of K-crotonate was placed in a Pyrex tube (6 mm i.d. (x200 mm) and heated in a metal bath maintained at a constant temperature. The tube was evacuated through the reaction. After a given time the reaction tube was taken out of the bath and allowed to cool to room temperature. The heat-treated salt was weighed and dissolved in aqueous hydrochloric acid solution and extracted with ether. The ether extract was treated with diazomethane. The methyl ester derivatives of the products were subjected to analysis by gas chromatography using diethyl maleate as internal standard. 

Method 2 (p-nitrobenzyl ester). To the residue are added 3 ml of ethanol and a 20-fold excess of 1 -p-nitrobenzyl-3-p-tolyltriazene [43]. The contents are mixed, loosely covered and heated at a gentle reflux for 1 h. The solution is cooled and an aliquot portion is subjected to chromatography. The derivatives are non-polar compared to the reagent and the parent fatty acid, and may be separated on silica gel with non-polar solvents such as hexane-diethyl ether. HPLC should also be useful with a system similar to that used for the benzyl esters. The limits of detection of the p-nitrobenzyl derivatives should be significantly lower than those of the benzyl esters. 

The most widely applied procedure is indirect quantification by extracting the fractions from the adsorbent layer in the presence of an internal standard, transmethylating, and subjecting the methyl esters of the fatty acids to gas chromatography (GC) analysis. Information is simultaneously obtained on the composition of the fractions and their absolute amounts. In practice, the sample is resolved on a preparative plate, each distinct zone is carefully scraped off, a standard solution of the internal standard (usually an odd-chain fatty acid methyl ester) is added, and the material is extracted with a suitable polar solvent such as diethyl ether or a chloroform-methanol mixture. More complicated extraction procedures are sometimes needed for polar complex lipids. Fatty acid methyl esters... 

Representative Chemicals Di-(2-ethylhexyl) phthalate (DEHP) Diisononyl phthalate (DINP) Diethyl phthalate (DEP) Di-N-butylphthalate Dimethylphthalate Methyl-glycol phthalate Phthalic acid Bis(2-methoxyethyl) ester. Eor the purposes of this article, the focus will be on DEHP, which is the most widely used phthalate, with some discussion of DINP since it has been the subject of controversy with regards to its possible adverse effects on children s health. 

Niobium V) reacts with thiocyanate in HCl solutions to form a yellow complex, which has been a basis of determining Nb. The niobium is determined spectrophotometrically either after extraction of the complex [34-36] or in an aqueous acetone medium. The sensitivities in both cases are similar, but the extraction method is less subject to interference by other metals. Diethyl ether is commonly used as the solvent, but ketones, esters, and higher alcohols are also suitable. 

Dialkyl l-(hydroxycarbonyl)methylphosphonates have been the subject of numerous investigations, with the efforts largely confined to diethyl l-(hydroxycarbonyl)methylphosphonate, whose reactivity parallels that of a-substituted derivatives. Several procedures for the synthesis of diethyl 1-(hydroxycarbonyl)methylphosphonate have been developed. They include the hydrogenolysis of the benzyloxycarbonyl ester (EtOH, Pd/C, H2), the alkaline hydolysis of alkoxycarbonyl ester (KOH or NaOH, EtOH, room temperature), and the addition of carbon dioxide to... 

The ester cleavage of fenitrothion leads to the formation of the metabolite 3-methyl-4-nitrophenol (MNP). Shafik et al. used GC-ECD for the detection of MNP in occupationally exposed subjects. Sample preparation involved extraction with diethyl ether, derivatization with diazoethane and purification on silica gel columns. The LOD was determined as 50 pgL with a recovery of 88-98%. 

Workers at the India Orchid company have shown that the condensation of 2-pentanone with diethyl oxalate may be catalyzed by sodium methoxide which is cheaper than sodium ethoxide. After further condensation with hydrazine hydrate, the pyrazole 18 was obtained as a mixture of methyl and ethyl esters. Methylation with dimethyl sulfate was performed neat, as in the Pfizer medicinal chemistry synthesis. The mixture of the methylated pyrazoles 19 was then nitrated and subjected to ammonolysis to give the desired pyrazole intermediate 5 (Scheme 16.8). 

Chloroform reacts with triethyl phosphite in a peroxide-catalysed reaction that leads exclusively to the competing product diethyl ethylphosphonate.275 On the other hand, carbon tetrachloride and the same ester give a high yield of the expected (trichloromethyl)phosphonate if boiled in the absence of radical-formers276 or subjected to UV-irradiation in the cold.277... 

The EtOH extracts of the wood of S. sachalinensis was fractionated with diethyl ether and the solubles subjected to silica-gel column and preparative thin-layer chromatographies to give (+)-syringaresinol and two lignan esters 23 and 24. 

Interaction of 3-chloro-4-fluoroaniline with diethyl ethoxy-methylene malonate yields the corresponding imine salt, which on being thermally cyclized gives rise to the formation of ethyl-7-ehloro-6-fluoro-4-hydroxyquinoline-3-carboxylate. The resulting produet on being subjected to N-alkalation, followed by the nucleophilic displacement of the 7-chloro moiety with N-methylpiperazine, and finally hydrolysis of the ester yields the desired product ofloxacin. 

Quantitative recoveries of endogenously labeled bile acids in homogenized human feces can be obtained by continuous extraction for 48 hr with hot chloroform-methanol, 1 1 (18). After saponification, acidification, and continuous diethyl ether extraction, the bile acids are purified on silicic acid (Section IIIB 4 and Ref. 18) to give one mono- and disubstituted, and one trisubstituted bile acid fraction. For identification purposes further subfractionation can be made [see Table V (69, 77, 126, 127)]. The subfrac-ticns are subsequently subjected to small-scale preparative thin-layer chromatography of methylated bile acids. The fractions eluted from the thin-layer plates are next subjected to peak-shift analyses followed by final identification by gas chromatography-mass spectrometry. When the fecal bile acid composition has been elucidated in this way the mono-, di- and trisubstituted bile acids from the first silicic acid column may be quantitated after methyla-tion and by analysis on QF-1. These results are then compared with those obtained after trifluoroacetylation of the bile acid methyl esters. (18). 

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