Oxygen nucleophiles Oxymercuration

These reactions are solvomercurations when the participating nucleophile is a part of the solvent. The terms oxymercuration for addition of oxygen nucleophiles, aminomer-curation for addition of amines, peroxymercuration for addition of OjH or OjR, etc., are used. 

In Chapter 15, we saw that we can convert an alkene to an alcohol by oxymercuration-demercuration. If we perform oxymercuration-demercuration of an alkene in an alcohol as the solvent, the product is an ether. In this reaction, the alcohol, rather than water, acts as the nucleophile. This process, called alkoxymercuration, occurs by a mechanism analogous to oxymercuration. First, electrophihc addition of Hg(OAc)2 to the carbon-carbon double bond forms a mercurinium ion intermediate, which is subsequently attacked by the nucleophilic oxygen atom of the alcohoL... 

However, before NaBH4 is introduced, 4 can also continue to react under the oxymercuration conditions, where Hg(OAc)2 can behave as a Lewis acid. As shown, the Hg(OAc)2 can interact with the oxygen atom of the epoxide group, much like an epoxide interacts with a proton, to facilitate the intramolecular nucleophilic attack by the nearby hydroxyl group. This intramolecular cyclization reaction forms a five-membered ring. A final proton transfer step, followed by the demercuration step, results in one of the major cyclization products, 8. 

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