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.^[1][2]

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Reaction mechanism

The reaction between silver benzoate (1) and iodine is very fast and produces a very reactive iodinium benzoate intermediate (2). The reaction of the iodinium salt (2) with an alkene gives another short-lived iodinium salt (3). Nucleophilic substitution (S_N2) by the benzoate salt gives the ester (4). Another silver ion causes the neighboring group substitution of the benzoate ester to gives the oxonium salt (5). A second S_N2 substitution by the benzoate anion give the desired diester (6).

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.

References

See also

• Woodward cis-hydroxylation