Prdvost reaction

Anthracene is noncarcinogenic and is structurally incapable of forming a bay region diol epoxide. Anthracene 1,2-dihydrodiol is most conveniently synthesized from 2-anthranol by oxidation with phenylseleninic anhydride to anthracene 1,2-dione (55) followed by reduction with NaBH in ethanol (22) or LiAlH (55). Anthracene 1,2-dihydrodiol has also been synthesized via the Prdvost reaction route... 

Nitrosonium ion was found to promote iodination of cyclohexene when AcOH was used as solvent, the trans-iodo acetoxy derivative was formed in a good yield. Solvolysis of the latter, followed by saponification, led to a cA-diol so that this method can serve as an alternative to the wet-Prdvost reaction. The NO+ cation is believed to promote the formation of some positive iodine species (equation 1). Oxidation by oxygen leads to the regeneration of iodine and NO+ from nitrosyl chloride189. 

Anti hydroxylation of an alkene is readily achieved with peroxycarboxylic acids. - Acid-catalyzed ting opening of the initial product, an oxirane (epoxide), forms the monoester of a 1,2-diol, hydrolysis of which affords the parent diol. Alternative reagents which are often used for anti hydroxylation of alkenes are hydrogen peroxide with oxides of timgsten - or selenium, - and iodine-silver benzoate (Prdvost reaction). ... 

The key steps in the first total synthesis of (+)-momilactone A by P. Deslongchamps et al. were a highly diastereoselective transannular DIels-Alder cycloadditlon and the Prdvost reaction The 3-ketolactone moiety was installed by first treating the tricyclic alkene with A/-bromo acetamide and silver acetate to obtain the trans bromoacetate with excellent diastereoselectivlty. The cIs stereochemistry of the lactone was achieved a few steps later by the intramolecular nucleophilic displacement of the bromide with the carboxylate ion on the adjacent six-membered ring. 

The alkene 11 reacts with electrophiles on the less-hindered (exo) face of the double bond. Thus, catalytic osmium tetroxide andNMO (seeScheme 5.80) or KMn04 provide the exo-cis-diol resulting from approach of the osmium from the more accessible face of the molecule. To prepare the isomeric endo-cis-diol, the Woodward-Prdvost reaction may be used (iodine and silver acetate in the presence of water). In this case, iodine should approach the exo face, but subsequent attack on the exo-iodonium ion by acetate anion would occur from the opposite (endo) face (see Scheme 5.93). Formation and hydrolysis of the cyclic intermediate cation gives the endo-cis-d o. ... 

The value of these reagents results from their specificity and the mildness of the reaction conditions. The reaction proceeds through the formation of an iodonium ion which, in the presence of carboxylate and silver ions, forms the resonance-stabilized cation 93 (5.93). Attack on the cation by the carboxylate anion in an Sn2 process gives the trans-diacyl compound. In the presence of water, however, a hydroxy acetal is formed this breaks down to gives the c/s-monoacylated diol. Note that with conformationally rigid molecules, or indeed with any alkene in which there is a preference for initial attack on one of the two faces of the double bond, the cis-diol obtained by the Woodward-Prdvost method may not have the same configuration as that obtained with osmium tetroxide. Related procedures, that avoid the use of expensive silver salts, have been reported with, for example, iodine and thallium(I) acetate or bismuth(III) acetate. 

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