Sodium hydrogen carbonate solution preparation

Dimethylphenylsilyl lithium (1 mmol, above THF solution) was added to copper(i) iodide (0.5 mmol) at — 23 °C, and the mixture was stirred at this temperature for 4h. The enone (0.75-0.5mmol) was then added, and stirring was continued at —23 °C for 0.5 h. The mixture was then poured on to ice(25 g)/HCl(5 ml), and extracted with chloroform (3 x 25 ml). The combined extracts were filtered, washed with HCI (25ml, 3m), water (25 ml), saturated sodium hydrogen carbonate solution (25 ml) and water (25 ml), and dried. Concentration and purification by preparative t.l.c. (eluting solvent 3 7 ether petrol) gave the /J-silylketone (40-99%). 

A solution of 4,4-dimethyl-l-trimethylsilylcyclohex-l-ene (2 mmol) in dichloromethane (100 ml) was added over 6 h with stirring to a mixture of acetyl chloride (6 mmol) and A1C13 (6 mmol) in dichloromethane (20 ml). After a further 15 min, the mixture was washed with saturated sodium hydrogen carbonate solution and brine, dried and concentrated in vacuo. Preparative t.l.c. on Si02, eluting with dichloromethane, gave 1-acetyl-4,4-dimethylcyclohex-l-ene (0.154 mmol, 77%). 

Aerosil was converted into the sodium form by treating it with a buffer solution (pH = 8.4) made of sodium hydroxide and sodium hydrogen carbonate solutions, after which it was filtered, washed free of alkali, and dried. This sodium-exchanged aerosil was then suspended in a solution of Ni(en)3(N03)2 prepared by adding the calculated amount of ethylene-diamine to a solution of nickel nitrate. The suspension was agitated for about 30 min and filtered off. The catalyst was then washed and dried at 100°C. 

Ethyl nitrite may be prepared by dissolving 38 g (0.55 mol) of sodium nitrite in 120 ml of water in a 500-ml flask equipped as above. Dilute 23 g (29 ml, 0.5 mol) of ethanol with an equal volume of water, carefully add 25 g (13.5 ml) of concentrated sulphuric acid and dilute to 120 ml with water. Cool both solutions to —10 °C in an ice-salt bath and add the acid-alcohol mixture to the nitrite solution slowly with constant stirring during about 30 minutes. Transfer the reaction mixture to a cooled separating funnel, run off- the lower aqueous phase, wash the ethyl nitrite layer rapidly with ice-cold 2 per cent sodium hydrogen carbonate solution and dry over anhydrous sodium sulphate. The product may be kept at 0°C as a 50 per cent solution in absolute ethanol if required but should be used as soon as possible. The b.p. of pure ethyl nitrite is 17 °C. 

General procedure for the preparation of oxathiolanes.140 To a stirred refluxing solution of cycloheptanone (56.1 g, 0.5 mol) and 2-mercaptoethanol (29.1 g, 0.5 mol) in anhydrous ether (400 ml) was added dropwise over a 1-hour period boron trifluoride-etherate (71 g, 0.5 mol). After an additional hour of being heated under reflux, the solution was allowed to cool, washed with 0.1 m sodium hydrogen carbonate solution (2 x 100 ml) and once with saturated sodium chloride solution (100 ml), and dried over magnesium sulphate. After removal of the solvent under vacuum on a rotary evaporator, the residue was distilled under vacuum to yield a small forerun which was followed by 2-oxa-5-thiaspiro[4.6]undecane (79.2g, 92%), b.p. 77-78°C/1.2mmHg, n 5 1.5165. 

Cognate preparations. Sebacic acid (decanedioic acid). Dissolve 40 g (0.25 mol) of methyl hydrogen adipate in 100 ml of absolute methanol to which 0.1 g of sodium has been added. Pass a current of about 2.0 amps until the pH of the solution is about 8 (c. 5 hours) test with narrow-range indicator paper. Transfer the contents of the electrolysis cell to a 500-ml round-bottomed flask, render neutral with a little acetic acid and distil off the methanol on a water bath. Dissolve the residue in 150 ml of ether, wash with three 50 ml portions of saturated sodium hydrogen carbonate solution, then with water, dry over magnesium sulphate and distil under reduced pressure. Collect the dimethyl sebacate at 155°C/8mmHg it melts at 26 °C and the yield is 14.6-16.0 g (51-56%). 

Cognate preparations sulphuric acid catalyst. Ethyl butanoate. Use a mixture of 88 g (92 ml, 1 mol) of butanoic acid, 23 g (29 ml, 0.5 mol) of ethanol and 9g (5 ml) of concentrated sulphuric acid. Reflux for 14 hours. Pour into excess of water, wash several times with water, followed by saturated sodium hydrogen carbonate solution until all the acid is removed, and finally with water. Dry with anhydrous sodium sulphate, and distil. The ethyl butanoate passes over at 119.5-120.5 °C. Yield 40g (69%). An improved yield can be obtained by distilling the reaction mixture through an efficient fractionating column until the temperature rises to 125 °C, and purifying the crude ester as detailed above under methyl acetate. 

Cognate preparation. Ethyl phenylacetate. Place 75 g (74 ml, 0.64 mol) of benzyl cyanide (Expt 5.157), 125 g (153 ml) of rectified spirit and 150 g (68 ml) of concentrated sulphuric acid in a round-bottomed flask, fitted with an efficient reflux condenser. Reflux the mixture, which soon separates into two layers, gently for 8 hours, cool and pour into 350 ml of water. Separate the upper layer. Dissolve it in about 75 ml of ether (1) in order to facilitate the separation of the layers in the subsequent washing process. Wash the ethereal solution carefully with concentrated sodium hydrogen carbonate solution until effervescence ceases and then with water. Dry over 10 g of anhydrous calcium sulphate for at least 30 minutes. Remove the solvent by flash distillation and distil the residue from an air bath. The ethyl phenylacetate passes over at 225-229 °C (mainly 228 °C) as a colourless liquid the yield is 90 g (86%). Alternatively, the residue after removal of ether may be distilled under diminished pressure collect the ester at 116-118°C/20mmHg. 

The following procedure removes the isocyanide and gives a stable water-white compound. Shake the once-distilled benzyl cyanide vigorously for 5 minutes with an equal volume of warm (60 °C) 50 per cent sulphuric acid (prepared by adding 55 ml of concentrated sulphuric acid to 100 ml of water). Separate the benzyl cyanide, wash it with an equal volume of saturated sodium hydrogen carbonate solution and then with an equal volume of half-saturated sodium chloride solution. Dry with magnesium sulphate and distil under reduced pressure. 

Note. (1) This amino ester is prepared as the corresponding hydrochloride by heating (R)-cysteine hydrochloride in methanol saturated with hydrogen chloride, followed by evaporation (cf. Expt 8.7). The hydrochloride is partitioned between dichloro-methane and sodium hydrogen carbonate solution evaporation of the organic layer affords the pure amino ester which is used immediately. 

Cognate preparations. Ethyl formate. Reflux a mixture of 61 g (50 ml, 1.33 mol) of formic acid (98/100%) and 31 g (39.5 ml, 0.67 mol) of absolute ethanol for 24 hours. Attach a fractionating column to the flask, distil and collect the liquid passing over below 62 °C. Wash the distillate with saturated sodium hydrogen carbonate solution and saturate with salt before removing the ester layer. Dry with anhydrous sodium sulphate, filter and distil. The ethyl formate passes over at 53-54 °C. The yield is 36 g (72%). 

In the pyrone series this hydrolysis of the thione sulfur is a general reaction and the efficiency of the method is demonstrated by the many examples in the tables. The Hg adducts should be prepared first and then decomposed in an alkaline medium, such as sodium hydrogen carbonate solution.3, n> 13 In this way the parent compounds 3 and 6 became accessible, starting from 5 and 8.33,38,53... 

An alternative procedure is available for the preparation of iodocarbonates which utilizes homoallylic carbamates as the starting material. For example, (/f )-( )-5-(aminocarbonyloxy)-l-benzyloxy-2,8-nonadiene [12, R1 = ( )-CH2OBn R2 = (CH2)2CH = CH2 R3 = H]9 with two equivalents of iodine in a two-phase medium consisting of diethyl ether and sodium hydrogen carbonate solution at 20 CC affords the corresponding cyclic iodocarbonate 13, a precursor of 1,3,5-triols1 °, in 76% yield and 93 7 (cis1,traits ) selectivity. 

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