Sodium acetate hydrogencarbonate

A summary of the methods by which 29 has been converted into 1 by base-catalyzed cyclization is shown in Table I. The most attractive, base-catalyzed, cyclization procedure appears to be that using the salt of a weak acid, such as sodium hydrogencarbonate, sodium acetate, or related basic salts. L-xy/o-2-Hexulosonic acid (28) has been re-... 

A mixture of the crude oil of methyl 2-bromo-3- 4-[2-(5-ethyl-2-pyridyl)ethoxy]phenyl propionate (73.0 g) thiourea (14.2 g), sodium acetate (15.3 g) and ethanol (500 ml) was stirred for 3 hours under reflux. The reaction mixture was concentrated under reduced pressure, and the concentrate was neutralized with a saturated aqueous solution of sodium hydrogencarbonate, to which were added water (200 ml) and ether (100 ml). The whole mixture was stirred for 10 min to yield 5- 4-[2-(5-ethyl-2-pyridyl)ethoxy]benzyl -2-imino-4-thiazolidinone as crystals (0.3 g, 523.0%). Recrystallization from methanol gave colorless prisms, melting point 187°-188°C, dec. 

Either the Mohr titration or the adsorption indicator method may be used for the determination of chlorides in neutral solution by titration with standard 0.1M silver nitrate. If the solution is acid, neutralisation may be effected with chloride-free calcium carbonate, sodium tetraborate, or sodium hydrogencarbonate. Mineral acid may also be removed by neutralising most ofthe acid with ammonia solution and then adding an excess of ammonium acetate. Titration of the neutral solution, prepared with calcium carbonate, by the adsorption indicator method is rendered easier by the addition of 5 mL of 2 per cent dextrin solution this offsets the coagulating effect of the calcium ion. If the solution is basic, it may be neutralised with chloride-free nitric acid, using phenolphthalein as indicator. 

Oxidation of 3,4-dihydropyrimidin-2(l //)-oncs (DHPMs) with ceric ammonium nitrate (CAN) in acetic acid resulted in ethyl 2,4-dioxo-6-phenyltetrahydropyrimidin-5-carboxylates as the major product. However, DHPMs undergo a regioselective oxidation with CAN in the presence of sodium hydrogencarbonate in neutral aqueous acetone solution to yield ethyl 6-meihyl-4-aryl(alkyl)pyrimidin-2(l //)-one-5-carboxylates. A mechanism involving a nitrolic acid intermediate has been suggested.72... 

A solution of 1-dimethylaminonaphthalene (CAUTION possible carcinogen) (0.17 g, 1 mmol) in dry ether (2 ml) is stirred at room temperature as butyllithium ( 1.7 M in hexane, 4.5 mmol) is added. The mixture is stirred for 48 h and then cooled to 0° and kept at that temperature as butylmagnesium chloride (2 m in ether, 6.8 mmol) is added. After 20 min the mixture is cooled to -5° and maintained at this temperature for 4 h while dry oxygen is passed into the stirred solution. The mixture is poured into a stirred mixture of water (100 ml), acetic acid (10 ml) and zinc powder (1 g), and stirring is continued until effervescence ceases. The mixture is filtered, and the ethereal layer is separated, washed with saturated aqueous sodium hydrogencarbonate... 

Tilak et described the use of excess mixed carbonic anhydrides to force condensation reactions to completion followed by the destruction of the excess mixed anhydride via the addition of aqueous potassium hydrogencarbonate. Hydrolysis of the nnixed anhydride was rapid and the resulting protected dipeptide could be extracted into ethyl acetate in a high state of purity, leaving the excess amino acid derivative and the salts in the aqueous phase. Without further purification the protected dipeptide was N -deprotected and reacted with the next mixed anhydride, and the process repeated until the desired peptide was obtained. Beyerman et al. substantially expanded the scope of this procedure and named it the REMA method for peptide synthesis (Repetitive Excess Mixed Anhydride).P°1 These reaction conditions provide an excellent method to ensure complete reaction of the amine component as well as rapid reaction rates and minimal side products. However, care must be taken to ensure that the excess carboxylic acid component is soluble in sodium hydrogencarbonate solution, e.g. when Z-Asp(OBzl)-OH is the acid component, it is extracted into the ethyl acetate as the sodium salt along with the product. With the due precautions the yields of small peptides are so high that the method could be applied without purification of the intermediate products, that is, in a repetitive way. 

Acetonyltriphenylphosphonium bromide (0.05 mmol) was added to a mixture of the alcohol, or phenol, or amine or thiol (1 mmol) and acetic anhydride (1.5-2.0 mmol) and the mixture was stirred at room temperature for ca. 0.5-3.5 h. After complete disappearance of the starting material, as monitored by TLC, the mixture was quenched with a saturated hydrogencarbonate solution (2mL). Finally, the reaction mixture was extracted with ethyl acetate (20mLx3). The combined organic extract was washed with water and dried over anhydrous sodium sulfate. After removal of the organic solvent in a rotary evaporator, the crude residue was passed through a silica gel column to isolate the desired pure acetate. 

Copper(ll) acetate in refluxing methanol has been used to prepare 3-alkyl-5-methyl-6-phenyl-3,4-dihydro-l,2,3-triazin-4-ones 43 from 2-(alkylamino)-4-methyl-5-phenyl-l,2-dihydropyrazol-3-ones 277. Alternatively, this conversion may be reached, albeit in a slow reaction, using air oxygen in presence of sodium hydrogencarbonate (Equation 122) <2006EJ03021>. 

The reduction of several organic compounds with hydroorganosilane/organic acid systems has been studied in some detail. [544] Trifluoroacetic acid is the best proton donor, but sometimes acetic acid is used. The reduction occurs at 20-60°C, usually without a solvent. After the reaction, the product may be neutralised with base, usually an aqueous solution of sodium hydrogencarbonate, separated and distilled. The formation of a carbonium ion is decisive for the reduction of alkenes and cyclo alkanes, and this is more difficult when the alkene chains are straight. Alkenes and cycloalkenes which do not have a C substituent on the double bond do not react. The final products do not include esters of trifluoroacetic acid [545] (Scheme 4.1) ... 

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