Working up the reaction

Alternatively, place the mixture of alcohol and red phosphorus in a 500 ml. three-necked flask fitted with a mechanical stirrer, dropping funnel and double surface condenser. Heat the phosphorus - alcohol mixture to about 250°, and add the bromine whilst stirring vigorously. Work up the reaction product as above. 

Gngnard reagent is consumed but the only organic product obtained after working up the reaction mixture is ethyl acetoacetate Why" What happens to the Gngnard reagent" ... 

Hydroxy-B-homo-5a-cholestan-7-one acetate (54b) A solution of 3/3-hydroxy-5a-cholestan-7-one acetate (51b 5 g mp 146-148°) in dioxane-ethanol (100 ml, 1 1) is placed in a 250 ml three-necked flask equipped with a mechanical stirrer and thermometer and is cooled to 0° (iee-salt bath). Powdered potassium cyanide (7.3 g) is added portionwise with stirring. Acetic acid (8 ml) is then added dropwise with constant stirring over 30 min. The resultant mixture is stirred for 1 hr at 0° C and for an additional 2 hr at room temperature. It is then poured into ice water (200 g ice, 100 ml water) and after standing for 1 hr the precipitate is collected by filtration. The product is dissolved in ether (100 ml), the ether solution is washed with 5% sodium bicarbonate, water and dried over anhydrous sodium sulfate. The filtrate is evaporated at reduced pressure and the solid residue (5.1 g) is crystallized from ethyl acetate (30 ml) to yield 2.8 g of cyanohydrin (52b) mp 160-164° repeated crystallization from the same solvent gives a product mp 164-167°. An alternative method of isolation of the cyanohydrin is used when 100 g or larger quantities are worked up. The reaction mixture is poured directly into a mixture of ice water and sodium bicarbonate, the precipitate (mp 155-156°) is washed well with water, dried and used directly for the next step. 

One of the most important applications of diazomethane depends on its ability to replace a mobile hydrogen atom by a methyl group. In comparison with other methylation agents, diazomethane occupies a rather special place this is, in part, because only rather strongly acidic protons are replaced. Because of the simple method of working up the reaction mixture, the reaction is especially well applicable for sensitive compounds and for small amounts. If tautomeric or potentially tautomeric compounds are treated with diazomethane, two... 

Before working up the reaction mixture, it is recommended to test whether the reaction is complete by thin layer chromatography (Note 6). If (F)-stilbene is observed, the reaction should be interrupted immediately. The checkers found that the work-up was complicated by formation of emulsions. Small quantities of brine were used to aid separation of the phases. 

A-Silylaldimine condensation with the lithiated intermediate 16 (Scheme 6), after working up the reaction under acidic conditions, produced an amino alcohol that can then be dehydrated to the benzo[d]azepine system 17 (R = Ph) <00JHC1061>. 

The mixture of the reaction products can be shifted from oxidation to reduction products depending on the method chosen to work up the reaction mixture, and can include chain scission products such as alcohols, aldehydes, ketones, carboxylic acids, and diacids. 

The alcohol (10 mmol) and methyl iodide (11 mmol) were added to a two-phase system of CS2 (10 ml) and 50% aqueous NaOH (from 5 g NaOH in 5 ml H20) containing n-Bu4NHS04 (lmmol) in a 50 ml round-bottomed flask. The mixture was stirred vigorously at room temperature by a magnetic stirrer. The reaction was monitored by checking the H NMR spectrum of the CS2 layer. To work up the reaction, the CS2 layer was separated and the aqueous layer extracted three times with CS2 (3 X10 ml). The combined CS2 layers were dried (Na2S04) and filtered. Evaporation of the solvent under reduced pressure afforded pure 0-alkyl 5-methyl dithiocarbonate (Table 2.5). Further purification could be carried out by column chromatography on silica gel or recrystallization for solid samples. 

Diiodoalkenes (cf., 4, 550).2 These alkenes are obtained in 60-85% yield by reaction of P(C6H5)3 and CI4 with an aldehyde in CH2C12 for 2 hours, after which Zn is added to facilitate the work-up. The reaction fails with ketones. 

If 10 gms. of fused sodium acetate (see p. 503) are added to the reaction mixture, the time of heating can be shortened to 6 hours. An older method of working up the reaction product was to distil fractionally the mixture of acetanilide and excess acetic acid, the former coming over at 280°, and being then recrystallised (A. Ch., [3], 37, 328). 

The mechanism for this reaction is slightly different from that presented previously for the reduction of benzene. First an electron is added to the pi antibonding MO to produce a radical anion. Because there is no alcohol to protonate this anion, a second electron is then added to produce a dianion. The dianion is a strong enough base to remove a proton from the ammonia solvent, producing an enolate anion. The enolate anion is stable to the reaction conditions until acid is added to work up the reaction. 

This is a hydroboration reaction, and the oxygen comes from the peroxide used to work up the reaction. You can read more about 9-BBN, and see its structure, on p. 1283 of Chapter 47. 

Furthermore, in this synthesis the polymer-supported reagents were encapsulated in sealed pouches to aid work-up. The reaction sequence starting from the acid chloride 2 through to the intermediate nitroalkene 3 could thus be performed in a one-pot procedure. The reaction progress as effected by the pouched reagent could be easily monitored by... 

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