Alkoxy mercuration

After inorganic mercuric salts are absorbed and dissociated into the body fluids and in the blood, they are distributed between the plasma and erythrocytes. Aryl mercuric compounds and alkoxy mercuric compounds are decomposed to mercuric ions, which behave similarly. 

Alcohols add directly to alkenes under acid or metal catalysis, or under photoinitiated conditions to give dialkyl ethers. Although these additions provide certain ethers under rather mild conditions, alkoxy-mercuration-demercuration is generally a superior method. 

Hydroxy- and alkoxy-mercurals (170), readily available by oxymercuration of the corresponding a,6 unsaturated esters, can be... 

With Lewis acids as catalysts, compounds containing more than one alkoxy group on a carbon atom add across vinyl ether double bonds. Acetals give 3-alkoxyacetals since the products are also acetals, they can react further with excess vinyl ether to give oligomers (228—230). Orthoformic esters give diacetals of malonaldehyde (231). With Lewis acids and mercuric salts as catalysts, vinyl ethers add in similar fashion to give acetals of 3-butenal (232,233). 

Alkyl mercury compounds in the blood stream are found mainly in the blood cehs, and only to a smah extent in the plasma. This is probably the result of the greater stabhity of the alkyl mercuric compounds, as well as their pecuflar solubiUty characteristics. Alkyl mercury compounds affect the central nervous system and accumulate in the brain (17,18). Elimination of alkyl mercury compounds from the body is somewhat slower than that of inorganic mercury compounds and the aryl and alkoxy mercurials. Methylmercury is eliminated from humans at a rate indicating a half-life of 50—60 d (19) inorganic mercurials leave the body according to a half-life pattern of 30—60 d (20). Elimination rates are dependent not only on the nature of the compound but also on the dosage, method of intake, and the rate of intake (21,22). 

The threo stereoisomer was the major product obtained by the synthesis in Scheme 13.14. This stereochemistry was established by the conjugate addition in Step A, where a significant (4-6 1) diastereoselectivity was observed. The C(4)-C(7) stereochemical relationship was retained through the remainder of the synthesis. The other special features of this synthesis are in Steps B and C. The mercuric acetate-mediated cyclopropane ring opening was facilitated by the alkoxy substituent.19 The reduction by NaBH4 accomplished both demercuration and reduction of the aldehyde group. 

After treatment of XXXVI with aqueous barium hydroxide, the liquor contained formic, methoxyacetic, and ethoxyacetic acids, methoxyacetone, and ethoxyacetone, produced by the two modes of cleavage XXXVIa and XXXVIb. Formic acid was converted with red mercuric oxide to carbon dioxide this was recovered as barium carbonate, the radioactivity of which was a measure of the C14 incorporated into Cl of kojic acid in the biosynthetic process. The alkoxyacetones were removed from the liquor by steam distillation, and converted to iodoform and a mixture of methoxy- and ethoxy-acetic acids. The iodoform was recovered by filtration its radioactivity indicated the proportion of C14 incorporated into C4. The alkoxy-... 

Furthermore, more recent work about the monoalkoxymercuration of a series of conjugated dienes with different mercury salts has shown157 that the alkoxymercuration of these compounds proceeds in two steps, the first being the formation of 1,2-adducts in which, with the exception of the mercuration of a-terpinene, the alkoxy group occupies the allylic position. The 1,2-alkoxymercurials are in equilibria with the corresponding... 

If 1-alkyl- or l-aryl-l,2-dihydro-X -phosphorins 147 (obtained by Method B, p. 78) are oxidized with mercuric acetate in the presence of alcohols or phenols as nucleophiles, it is possible to isolate X -phosphorins 156 in which the phosphorus bears a carbon substituent besides an alkoxy or phenoxy group (Markl ° ). 

The intramolecular alkoxy- or phenoxy-mercuration of unsaturated alcohols or phenols, respectively, provides an exceptionally useful process for the formation of cyclic ethers, particularly those bearing a five- or six-membered ring (equation 263).415... 

The stereodirecting effect of the allylic alkoxy-substituent (290-292) on cycloamido-mercuration has been found to be surprisingly high (>4 kealmol-1)419. 

When mercuration takes place in an alcohol solvent, the alcohol serves as a nucleophile to attack the mercurinium ion. The resulting product contains an alkoxy (—O—R) group. In effect, alkoxymercuration-demercuration converts alkenes to ethers by adding an alcohol across the double bond of the alkene. 

Addition of mercury and an alkoxy group to a double bond, usually by a solution of mercuric acetate in an alcohol. Alkoxymercuration is usually followed by sodium borohydride reduction (demercuration) to give an ether, (p. 636)... 

Mercuric trifluoroacetate, Hg(02CCF3)2i Adds to alkenes in the presence of alcohol, giving a-alkoxy organomercury compounds that can be reduced with NaBH4 to yield ethers. The overall reaction effects a net addition of an alcohol to an alkene (Section 18.2). 

Mercurated 1-acyloxy or 1-alkoxy-vinylphosphonates have been synthesized by the reaction of trialkyl phosphite-mercury (II) chloride complexes with ketene " or alkynyl ethers, respectively (equation 95). 

Glyceraldehyde, CHOCH(OH)CH20H, similarly condenses with DAMN to give a mono-imine which can be cyclized (with mercuric chloride), affording 2,3-dicyano-5-methylpyrazine other similar reactions are discussed. 2-Alkoxy-6-aminopyrazines (264) are obtained upon treatment of N-nitrosobis(cyanomethyl)amine (263) with sodium alkoxides. The nitroso-group is essential, which suggests that the reaction may proceed as outlined in Scheme 105. ... 

P3o-idine-I-oxides are comparatively resistant to reduction because of resonance stabilization by the aromatic system. Typical reagents that have been used for the formation of pyridones and pyridinols are Raney Nickel in methanol, palladium-on-charcoal, phosphorous trichloride, or phosphorus oxychloride in ethyl acetate. The N-oxides of pyridoxine, pyridoxal, and pyridoxamine have been deoxygenated catalytically. 4-Alkoxy-3-halopyri-dine-1-oxides are A-deoxygenated by phosphorous trichloride in chloroform. 2-Amino-3-pyridinol can be prepared ffom2-nitro-3-pyridinol-l-oxide (X1I450) in acetic acid by treatment with iron and mercuric chloride and then with zinc. 2-Halo-3-pyridinols can be prepared from XII-450 by treatment with phosphorous trihalides in chlorofiMm ... 

As well as alkoxy- and aryloxy-groups, the corresponding sulphur functions have been replaced in the amination of pyridine l-oxides s and quaternary pyridinium salts Examples with pyridines are rare" . An interesting intramolecular amination occurs in the transformation of 2-pyridyl-2 -(3 -aminopyridyl)thioether into 3-(2 -pyridylamino)pyridine-2-thiol 09 l-Alkylpyrid-2>thiones, warmed with alcoholic ammonia and mercuric oxide, give l-alkylpyrid-2-one-imines ii. 

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