Organic synthesis water

Examples of possible photocatalytic applications developed on an laboratory scale cover a very broad range [125,126] from direct H2 production from water, selective organic synthesis, water treatment and air cleaning to disinfection and anti-tumoral... 

HyPure. [Olin] Chloric and hypochlor-ous acid, lithium, potassium, or sodium hypochlorites for bleaching, organic synthesis, water treatment, hard surface cleaners. 

A few years after the first articles of Breslow had appeared, Grieco elegantly demonstrated that the astonishing rate and selectivity enhancements of Diels-Alder reactions in water can be exploited sirccessfully in organic synthesis. He extensively studied the reactivity of dienes containing... 

When esterification is the objective water is removed from the reaction mixture to encourage ester formation When ester hydrolysis is the objective the reaction is carried out m the presence of a generous excess of water Both reactions illustrate the applica tion of Le Chatelier s principle (Section 6 10) to organic synthesis... 

Dichloroacetic acid [79-43-6] (CI2CHCOOH), mol wt 128.94, C2H2CI2O2, is a reactive intermediate in organic synthesis. Physical properties are mp 13.9°C, bp 194°C, density 1.5634 g/mL, and refractive index 1.4658, both at 20°C. The Hquid is totally miscible in water, ethyl alcohol, and ether. Dichloroacetic acid K = 5.14 X 10 ) is a stronger acid than chloroacetic acid. Most chemical reactions are similar to those of chloroacetic acid, although both chlorine... 

P-Hydroxy acids lose water, especially in the presence of an acid catalyst, to give a,P-unsaturated acids, and frequendy P,y-unsaturated acids. P-Hydroxy acids do not form lactones readily because of the difficulty of four-membered ring formation. The simplest P-lactone, P-propiolactone, can be made from ketene and formaldehyde in the presence of methyl borate but not from P-hydroxypropionic acid. P-Propiolactone [57-57-8] is a usehil intermediate for organic synthesis but caution should be exercised when handling this lactone because it is a known carcinogen. 

Chemical tests for particular types of impurities, e.g. for peroxides in aliphatic ethers (with acidified KI), or for water in solvents (quantitatively by the Karl Fischer method, see Fieser and Fieser, Reagents for Organic Synthesis J. Wiley Sons, NY, Vol 1 pp. 353, 528, 1967, Library of Congress Catalog Card No 66-27894). 

A detailed procedure for the use of MCPBA recently appeared in Reagents for Organic Synthesis by Fieser and Fieser. The commercially available MCPBA (Aldrich) is 85% pure the contaminant, m-chlorobenzoic acid, can be removed by washing with a phosphate buffer of pH 7.5. The epoxidation is usually performed as follows a solution of 3 -acetoxy-5a-androst-16-ene (2.06 g, 6.53 mmoles) in 25 ml of chloroform (or methylene dichloride) is chilled to 0° in a flask fitted with a condenser and drierite tube and treated with a solution of commercial MCPBA (1.74 g, 20% excess) in 25 ml chloroform precooled to the same temperature. The mixture is stirred and allowed to warm to room temperature. After 23 hr (or until TLC shows reaction is complete) the solution is diluted with 100 ml chloroform and washed in sequence with 100 ml of 10% sodium sulfite or sodium iodide followed by sodium thiosulfate, 200 ml of 1 M sodium bicarbonate and 200 ml water. The chloroform extract is dried (MgS04) and evaporated in vacuo to a volume of ca. 10 ml. Addition of methanol (10 ml) followed by cooling of the mixture to —10° yields 0.8 gof 16a,17a-epoxide mp 109.5-110°. Additional product can be obtained by concentration of the mother liquor (total yield 80-90%). 

The overall result of the sequence hydroboration -I- oxidation is a regioselective and-Markownikoff-addition of water to an alkene. This reaction is an important method in organic synthesis, since it can be made stereoselective and even enantioselective. 

Because the anioas of nitroalkanes are stable, retro-acyladoc smoothly In the presence of a base catalyst. This type of reacdo organic synthesis." Nucleophilic attack of water or alcohol to ct-the ring cleavage v/ith the formadon of Oj-nitro acids and Oj-niti... 

The charged group introduced into products by the aldol donors (phosphate, carboxylate) facilitates product isolation and purification by salt precipitation and ion exchange techniques. Although many aldehydic substrates of interest for organic synthesis have low water solubility, at present only limited data is available on the stability of aldolases in organic cosolvents, thus in individual cases the optimal conditions must be chosen carefully. 

In organic synthesis, we know only one interesting case where reactions of arenediazonium ions take place in the presence of a crown ether, but not at all without. It is the azo coupling reaction of 4-methoxybenzenediazonium tetrafluoroborate with pyrroles. Butler and Sheppard (1978) reported that the azo derivatives 11.15 and 11.16 were obtained under phase-transfer conditions (CH2C12 or CHC13 + water) in the presence of dicyclohexano-18-crown-6, but not at all by a published procedure (Kreutzberger and Kalter, 1961). 

The blue samarium diiodide solutions are stable indefinitely in the absence of water and oxygen, and Sml and Ybl2 solutions have been employed as reducing agents in organic synthesis. 

Fringuelli F., Pizzo F. Water-Facilitated Organic Reactions in Seminars in Organic Synthesis. 17th Summer Sch A. Corbella 1992 86, Pb. Polo Ed. Chim. Milan Keywords Diels-Alder reactions... 

Linear non-cross-linked polystyrene has been used for organic synthesis since it is readily soluble in common organic solvents (i.e., dichloromethane, chloroform, tetrahydrofuran, toluene, ethyl acetate, and pyridine) but precipitates upon addition of water or methanol [123-126]. However, no examples of the use of this polymer in conjunction with microwave chemistry have been reported. 

Lubineau A, Aug6 J (1999) Water as Solvent in Organic Synthesis. 206 1-39 Lundt I, Madsen R (2001) Synthetically Useful Base Induced Rearrangements of Aldonolac-tones. 215 177-191... 

Rare Earth Metal Trifluoromethanesulfonates as Water-Tolerated Lewis Acid Catiaysts Organic Synthesis," Kobavashi. Synlett, 1994, 679... 

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