Silver benzoate initiator

The same result can be achieved in one step with m-chloroperoxybenzoic acid and water.719 Overall anti addition can also be achieved by the method of Prevost. In this method the olefin is treated with iodine and silver benzoate in a 1 2 molar ratio. The initial addition is anti and results in a 3-halo benzoate (71). These can be isolated, and this represents a method of addition of IOCOPh. However, under the normal reaction conditions, the iodine is replaced by a second PhCOO group. This is a nucleophilic substitution reaction, and it operates by the neighboring-group mechanism (p. 308), so the groups are still anti ... 

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 use of transition metal species can lower appreciably the decomposition temperature of ot-diazo-carbonyl compounds they can also alter the reactivity of the carbene intermediate (resulting from the initial nitrogen elimination see Section 3.9.2.1) by complex formation. Hence, the Wolff rearrangement may occur with difficulty or, usually, not at all. Thus, some copper species (excepting, for example, Cul), or Rh and Pd catalysts are inappropriate. Freshly prepared silver(I) oxide has been used most frequently, but silver salts (especially silver benzoate) are sometimes preferred.Silver-based catalysts are usually employed in combination with an alkaline reagent e.g. sodium carbonate or a tertiary amine). Even under silver catalysis competing reactions may be observed, and sometimes the products of Wolff rearrangement may not be obtained (see Section 3.9.2.3). 

By inspection one can see that the the 2R,3S and 2S,3R isomers are enantiomers and the 2R,3R and 2S,3S pair are enantiomers. As they are drawn, one can see the original E stereochemistry of the double bond. Thus the first pair comes from a stereospecific trans addition across the double bond while the second pair comes from a stereospecific cis addition. Clearly the stereochemistry of the double bond is maintained throughout the addition. Since iodine is the electrophile, a bridged iodonium ion is likely responsible. The initial addition gives only a single pair of enantiomers since the only nucleophile is benzoate. Also noted is that iodine is not in the product so something must replace the iodine. The silver ion would help to remove the iodine. Since iodine would cause a trans addition and the product has oxygens added trans, there must be a replacement of iodine by an... 

If hydroxamoyl chlorides are treated with the silver salt of benzoic acid the N-benzoate XVIII is obtained via rearrangement of the initially formed O-benzoate XIX... 

Within a few days, we found a reliable reaction protocol in which a combination of the benzoic acid and aryl bromide in NMP is stirred for several hours at 120°C in the presence of stoichiometric amounts of basic copper carbonate and potassium fluoride, molecular sieves, and 2 mol% of a Pd(acac)2/P( -Pr)Ph2 catalyst [36, 37]. The addition of molecular sieves, which effectively trapped the reaction water, allowed to deprotonate the benzoic acid in situ with carbonate bases. It was thus no longer necessary to use preformed and carefully dried copper benzoates. Beside copper, silver carbonate was also found to be effective, but due to the higher cost of this metal, we initially did not follow up on this. 

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