Reaction oxymercuration-demercuration

Oxymercuration/demercuration provides a milder alternative for the conventional acid-catalyzed hydration of alkenes. The reaction also provides the Markovnikov regiochemistry for unsymmetrical alkenes.33 Interestingly, an enantioselective/inverse phase-transfer catalysis (IPTC) reaction for the Markovnikov hydration of double bonds by an oxymercuration-demercuration reaction with cyclodextrins as catalysts was recently reported.34 Relative to the more common phase-transfer... 

A synthetic neuraminic acid derivative having a methyl ether group at 0-4 (Neu5Ac4Me) was synthesized by Beau and coworkers101,102 by using an oxymercuration-demercuration reaction.103 The metabolic behavior of this compound will be described in Sections V and VI. 

Cyclopropane rings can undergo the oxymercuration/ demercuration reaction H... 

Neutral cyclodextrins have been used as chiral phase-transfer catalysts for an interesting inverse phase-transfer catalysis reaction [50]. The Markovnikovhydration of the double bond by an oxymercuration-demercuration reaction has been demonstrated in the presence of cyclodextrins as chiral phase-transfer catalysts to obtain products in low to moderate enantioselectivity (Scheme 7.16). The mercuric salts are water-soluble, and remain in the aqueous phase, whereas the neutral alkenes prefer an organic phase. A neutral cyclodextrin helps to bring the alkenes into the aqueous phase in a biphasic reaction, and also provides the necessary asymmetric environment. 

Alternatively, the mesylate 77 was treated with sodium iodide in refluxing 2-butanone to produce the olefin 90 (Scheme 3). " Oxymercuration-demercuration reaction of 90 using mercnric acetate-sodinm borohydride afforded a 1 1 mixture of 91 and 92. Compound 92 was mesylated, rednced and cyclized in boiling ethanol, in the presence of sodium acetate, to give 93. This was converted by standard steps into 94, and subsequent hydrolysis of 94 followed by oxidation with pyridinium chlorochromate afforded the lactone 95 (28% overall yield from 92), which was nsed in the synthesis of retronecine (22). " ... 

The challenge to the synthetic chemist that was posed by these structures was the control of C6 stereochemistry. An early solution to this problem involved the intramolecular oxymercuration-demercuration approach, as illustrated in Scheme 9 (46,58). Thus, the stereoselective cyclization of 38 to the tricycUc cannabinoid skeleton by means of the intramolecular oxymercuration-demercuration reaction (58,61) gave the 6P-isomer predominantly (6P 6a = 85 15). The enantiomers were separated by chiral high-performance liquid chromatography (HPLC) using Chiralpak OD columns. The probable... 

An organic chemist synthesized and isolated the above represented compound. If this compound undergoes oxymercuration-demercuration reaction, the major product is most likely ... 

The answer is B. The oxymercuration-demercuration reaction converts an alkene to an alcohol. The hydration follows Markovnikov s rule and thus the hydrogen adds to the carbon atom with greater number of hydrogens. 

Steric effects may play a role in the regiochemistry of the reaction as well. While the oxymercuration-demercuration reaction is generally considered to give only Markovnikov hydration, as shown by predominant formation of 43, this regioselectivity is not absolute. For example, methoxymercuration of 3,3-dimethyl-l-butene produced 2% of 3,3-dimethylbutyl methyl ether (44, equation 9.42). ... 

A biomimetic synthesis of the strobane carbon skeleton has been achieved using an oxymercuration-demercuration reaction on epimanool (Scheme 41). ... 

Reductive oxygenation (NaBH4, O2, DMF) of organomercurial (20) is known to afford alcohol (21) along with 5% of the by-product (22). If the reaction is performed with only a slow stream of air (rather than a vigorous flow of pure oxygen) the by-product (22) becomes the major product and is isolated in 68% yield. The radical (23) is postulated as an intermediate . An oxymercuration-demercuration reaction of a D-allal derivative is mentioned in Chapter 13. 

Oxymercuration Reactions.— Two research groups have drawn attention to the value of the oxymercuration-demercuration reaction when applied to unsaturated long-chain compounds ... 

In an oxymercuration-demercuration reaction, an alkene is treated with mercury(II) acetate, Hg(OAc)2, and the product is treated with sodium borohydride. The net result is a Markovnikov addition product in which the OH group bonds to the more substituted carbon atom of the alkene. 

Both alkyl groups of this disubstituted alkene are part of the ring and are bonded to the same carbon atom. The CH, unit has the less substituted carbon atom. An oxymercuration-demercuration reaction places a hydrogen atom at the CH, site and a hydroxyl group on the ring carbon atom. This product is the predicted Markovnikov product of indirect hydration of an alkene... 

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