Prévost reaction
The Prévost reaction is chemical reaction in which an alkene is converted by iodine and the silver salt of benzoic acid to a vicinal diol with anti stereochemistry. The reaction was discovered by the French chemist Charles Prévost.
The reaction between silver benzoate and iodine is very fast and produces a very reactive iodinium benzoate intermediate. The reaction of the iodinium salt with an alkene gives another short-lived iodinium salt. Nucleophilic substitution by the benzoate salt gives the ester. Another silver ion causes the neighboring group substitution of the benzoate ester to give the oxonium salt. A second SN2 substitution by the benzoate anion gives the desired diester.
In the final step hydrolysis of the ester groups gives the anti-diol. This outcome is the opposite of that of the related Woodward cis-hydroxylation which gives syn addition.
