Mercuration Solvomercuration

Mercury(II) trifluoroacetate is a good electrophile that is highly reactive toward carbon-carbon double bonds [52, 53, 54] When reacting with olefins in nucleophilic solvents, it usually gives exclusively mercurated solvoadducts, but never products of skeletal rearrangement Solvomercuration-demercuratton of alkenes with mercury(II) trifluoroacetate is a remarkably effective procedure for the preparation of esters and alcohols with Markovnikov s regiochemistry [52, 5J] (equation 24)... 

The solvomercuration of alkenes has been exhaustively studied and is now well understood. The mechanism of this reaction proceeds through two steps coordination of the mercuric ion to the alkene to form a fluxional cationic intermediate and subsequent nucleophilic anti-attack. Charge stabilization of the cationic intermediate constitutes one of the factors dictating the regioselectivity of the reaction (Scheme 11). 

Ring-closing reactions promoted by mercuric salts are valuable transformations which find an increasing use in the total synthesis of various natural products.130-140 Several examples of solvomercurations demonstrating the applicability of these transformations to the synthesis of natural product precursors are presented in Table 2. Piperidines (entry a), 141 pyrans (entries b-d), 142-144 and furans (entries e, f)14S>146 have been obtained in good yields and diastereoselectivity. These derivatives serve as starting materials for various natural products and can be demercu-rated under reducing conditions.147... 

Addition of electrophilic mercury(II) salts to carbon-carbon double bonds in nucleophilic solvents (i.e. oxymercuration, solvomercuration etc.) is a well documented methodology in organic synthesis146. In these reactions a mercuric salt, usually the chloride or... 

Whereas mercuration-demercuration of alkenes in the presence of water gives alcohols, in alcohol solvents (free from H,0) ethers result. These reactions in the presence of nucleophilic solvents such as water and alcohols are examples of solvomercuration. The mercuric salts usually used are the acetate, Hg(OAc), (—OAc is an abbreviation for —OCCH,) or the trifluoracetate. Hg(OCOCF,),. ... 

Solvomercuration,3111 484 187 or the addition of mercury(II) salts, is a convenient route to organomercurials. On the other hand, replacement of mercury with hydrogen allows Markovnikov functionalization of alkenes.488 A method called mercuration-demercuration, for instance, has been developed for the Markovnikov hydration of alkenes under mild conditions489 [Eq. (6.82)490] ... 

Stable mercurinium ions, often postulated as intermediates in solvomercuration reactions, have been observed for the first time.170 They may be prepared in media of low nucleophilicity either by direct mercuration or by ionization of a p-substituted organomercurial. For example, the ethylene mercurinium ion may be prepared from 2-methoxyethylmercuric chloride in an ionizing medium such as HS03F-SbF5-S02... 

Amides.1 The solvomercuration-demercuration of terminal olefins or cyclic olefins with acetonitrile and mercury 11) nitrate followed by reduction of the intermediate organomercury compound affords amides, hydrolyzable to amines. Neither mercuric acetate nor mercuric trifiuoroacetate is satisfactory in this reaction. Preliminary attempts to use a tertiary olefin failed. 

The chain terminal ethoxy group of compound 41 has been introduced by means of the solvomercuration-demercuration method (Brown, 1967 Brown and Min-Hon Rei, 1969). This process, based on the mercuration of olefin with mercuric... 

The oxjnnercuration reaction is thought to be a two-step process. In the first step, electrophilic attachment of the mercury ion to the alkene produces a positively charged intermediate (equation 9.39). In the second step of oxy-mercuration, a nucleophile (most likely a solvent molecule, SOH) reacts with the intermediate to produce the organomercury compoimd (equation 9.40). For reactions in water, both the organomercurial and the final product are alcohols. The reaction produces an ether if the hydroxylic solvent is an alcohol, and the reaction is called solvomercuration or alkoxymercuration. Better yields are obtained if the anion of the mercuric salt is a weaker nucleophile than is the solvent. For this reason, mercuric... 

Dialkylacetylenes and phenylalkylacetylenes also add mercuric acetate in acetic acid solution. The products point to exclusively anti addition, but with a regiochemistry that depends on the nature of the alkyl group. " The results suggest that the solvomercuration of alkynes appears to take place through mercurinium ions (e.g., 73), as does solvomercuration of alkenes. ... 

Solvomercuration of cyclohexene with mercuric nitrate in acetonitrile, followed by reduction with sodium borohydiide, leads to a product with the molecular formula CsHisNO. 

Mercuric chloride-sodium tetrahydridoborate Heterocyclics by intramolecular solvomercuration-demercuration... 

Aza-adamantanes.—1-Aza-adamantanes are easily available in a convenient two-step synthesis from a-pinene (Scheme 83)." The synthesis is dependent on the serendipitous discovery that solvomercuration-demercuration of a-pinene with acetonitrile in the presence of mercuric nitrate followed by in situ boro-hydride reduction led not to the expected allylic amide but instead to azabicy-clo[3,3,l]nonene which is readily converted into aza-adamantane by reaction with formaldehyde. Rearrangement of A-chloro-N-acetyl-l-aminoadamantane... 

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