Silver acetate esters

If chloride is present, saturated aqueous silver acetate solution should be added in amounts slightly more than the calculated quantity prior t o the addition of concentrated sulphuric acid. The procedure may be applied to the routine analysis of mixtures of nitric and sulphuric acids, and to the determination of nitrogen in esters such as nitroglycerine and nitrocellulose the latter are easily hydrolysed by strong sulphuric acid after dispersal in glacial acetic acid. 

The preparation of Pans-1,2-cyclohexanediol by oxidation of cyclohexene with peroxyformic acid and subsequent hydrolysis of the diol monoformate has been described, and other methods for the preparation of both cis- and trans-l,2-cyclohexanediols were cited. Subsequently the trans diol has been prepared by oxidation of cyclohexene with various peroxy acids, with hydrogen peroxide and selenium dioxide, and with iodine and silver acetate by the Prevost reaction. Alternative methods for preparing the trans isomer are hydroboration of various enol derivatives of cyclohexanone and reduction of Pans-2-cyclohexen-l-ol epoxide with lithium aluminum hydride. cis-1,2-Cyclohexanediol has been prepared by cis hydroxylation of cyclohexene with various reagents or catalysts derived from osmium tetroxide, by solvolysis of Pans-2-halocyclohexanol esters in a manner similar to the Woodward-Prevost reaction, by reduction of cis-2-cyclohexen-l-ol epoxide with lithium aluminum hydride, and by oxymercuration of 2-cyclohexen-l-ol with mercury(II) trifluoro-acetate in the presence of ehloral and subsequent reduction. ... 

A-Acyloxy-A-alkoxyamidcs 20 are synthesised from A-chlorohydroxamic esters 22 by replacement of chlorine by a carboxyl group (Scheme 3). Initially we employed silver acetate in anhydrous ether to make A-acetoxy derivatives.47 However, most have been made using sodium carboxylates in dry acetone by analogy with Finkelstein chemistry.5,38 40>42,43,46,48,49,i05 reacti0ns can be monitored conveniently by thin layer chromatography and A-acyloxy-A-alkoxyamides generally... 

As esters the alkyl halides are hydrolysed by alkalis to alcohols and salts of halogen acids. They are converted by nascent hydrogen into hydrocarbons, by ammonia into amines, by alkoxides into ethers, by alkali hydrogen sulphides into mercaptans, by potassium cyanide into nitriles, and by sodium acetate into acetic esters. (Formulate these reactions.) The alkyl halides are practically insoluble in water but are, on the other hand, miscible with organic solvents. As a consequence of the great affinity of iodine for silver, the alkyl iodides are almost instantaneously decomposed by aqueous-alcoholic silver nitrate solution, and so yield silver iodide and alcohol. The important method of Ziesel for the quantitative determination of alkyl groups combined in the form of ethers, depends on this property (cf. p. 80). 

Hydrolysis of the ester does not change the configuration. Woodward s method is similar, but results in overall syn hydroxylation. The olefin is treated with iodine and silver acetate in a 1 1 molar ratio in acetic acid containing water. Here again, the initial product is a 3-... 

Najera and Sansano et al. studied the reaction of acryl esters 63 of R- and 5- lactate (only S shown see Scheme 2.17).33 The reaction transpired at room temperature catalyzed by 10 mol% silver acetate in the presence of either 10 mol% KOH or triethylamine. Both methods afforded the endo products in moderate to good yields and excellent stereoselectivity. The auxiliary was cleaved by the action of aqueous base. In collaboration with the Cossio group, these authors have applied the method to synthesize a number of hepatitis C RNA polymerase inhibitors.34... 

In related reactions, Snapper and Hoveyda et al. reported an asymmetric version of Mannich-type reactions catalyzed by silver acetate.38,39 Propargyl imines proved to be susceptible to nucleophilic addition of sily lenol ethers derived from acetate esters in the... 

The Leukart reaction has also been used in the conversion of dehydroepiandro-sterone into 17/3-formylamino-3/3-formyloxyandrost-5-ene, which on reduction with lithium aluminium hydride afforded 3/3-hydroxy-17/3-me thylaminoandrost-5-ene. Acylation with isocaproyl chloride then furnished the N-methyl-N-isocaproyl steroid (197), after selective ester hydrolysis of the initially formed ON-diacyl derivative. The amide (197) was further converted into its 3,5-cyclo-6-ketone via the 3,5-cyclo-6/3-alcohol and thence by reaction with hydrogen bromide into the corresponding 3/3-bromo-5a-6-ketone which upon dehydrobromination furnished a A2-5a-6-ketone and ultimately the 2-monoacetate of the 2/3,3/3-diol (198) after reaction with silver acetate and iodine. Hydrolysis to the 2/3,3/3-diol (198) gave a separable mixture of the 2/3,3/8-dihydroxy-5a- and -5/3-ketones.88... 

Cyclization of diazonium salts using iodide ion had been well developed by Beckwith s group, but the iodide corresponding to 50 is a secondary neopentyl iodide, which would be impossible to convert by S 2 chemistry into an alcohol. Our efforts to convert similar iodides to acetate esters with silver acetate by S l have also not met with success. Even if such conversions were possible, they would still be much less direct than with the new radical-polar crossover methodology. 

Several related procedures for syn hydroxylation of alkenes involve a halohydrin ester (32) as the key intermediate. In Woodward s procedure an alkene in glacial acetic acid is treated with iodine and silver acetate. Acetyl hypoiodite, MeCOjI, formed by reaction of the latter two reagents attacks the alkene, R R 0=CR R in an electrophilic manner, from the less hindered side to give, by overall anti addition. 

Under basic conditions fluorinated carboxylic acids react with alkyl iodides " or bromides. Silver oxide seems to be the base of choice for the synthesis of difluoro(nuorosulfonyl)acetic esters 6 (from 5). ... 

In a similar way, when ethylene bromide is treated with silver acetate, CH3—COOAg, an acyl-ester of the corresponding di-hydroxy alcohol is obtained, which, on hydrolysis, yields the di-hydroxy alcohol itself, as follows ... 

Stereospecific hydroxylations can also be accomplished via silver acetates [781, 782] or silver benzoates [784] and iodine followed by hydrolysis of the intermediate esters. Depending on the reaction conditions, either syn or anti hydroxylation (acyloxylation) can be accomplished (equations 78 and 79). 

Woodward method The syn-hydroxylation of an alkene the first step involves treating the alkene with iodine and silver acetate in a 1 1 molar ratio in wet acetic acid. The hydrolysis of the intermediate c/////-P-halogenoester is via a normal SN2 reaction in which there is no neighbouring group effect because the ester function is solvated by the water. Overall //-addition may be achieved by the method of Prevost. 

Silicic acid, methyl ester of ortho- 3729 Silver acetate 3356... 

Readily available /3-hydroxy-esters (e.g. 49) can be converted into butyrolactones (e.g. 50) simply by treatment with concentrated sulphuric acid. Cyclic ether-lactones (52) are available from hydroxy-acids (51) by iodolactonization followed by dehalogenation with silver acetate. A stereoselective total synthesis of the antifungal mould metabolite (53) has been reported. ... 

Berzelius took as the equivalents of organic acids those weights combining with one atom or equivalent of silver oxide, but since he gave this the formula AgO (Ag = 2 x 108), all his molecular weights of the acids are double the true ones. If the formula of acetic acid is doubled, that of alcohol is also doubled, since acetic ester contains ether, C H 0, and so on. His difficulty with polybasic acids such as citric acid has been mentioned (p. 278). 

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