Mercury olefination

Loaded Adsorbents. Where highly efficient removal of a trace impurity is required it is sometimes effective to use an adsorbent preloaded with a reactant rather than rely on the forces of adsorption. Examples include the use of 2eohtes preloaded with bromine to trap traces of olefins as their more easily condensible bromides 2eohtes preloaded with iodine to trap mercury vapor, and activated carbon loaded with cupric chloride for removal of mercaptans. 

With mercuric acetate (Hg(OOCCH2)2), olefins and / fZ-butyl hydroperoxide form organomercury-containing peroxides (66,100). The organomercury compound can be treated with bromine or a mild reducing agent, such as sodium borohydride, to remove the mercury. 

Subsequent dehydrohalogenation afforded exclusively the desired (Z)-olefin of the PGI2 methyl ester. Conversion to the sodium salt was achieved by treatment with sodium hydroxide. The sodium salt is crystalline and, when protected from atmospheric moisture and carbon dioxide, is indefinitely stable. A variation of this synthesis started with a C-5 acetylenic PGF derivative and used a mercury salt cataly2ed cyclization reaction (219). Although natural PGI has not been identified, the syntheses of both (6R)- and (65)-PGl2, [62777-90-6] and [62770-60-7], respectively, have been described, as has that of PGI3 (104,216). 

Methyl ketones are important intermediates for the synthesis of methyl alkyl carbinols, annulation reagents, and cyclic compounds. A common synthetic method for the preparation of methyl ketones is the alkylation of acetone derivatives, but the method suffers limitations such as low yields and lack of regioselectivity. Preparation of methyl ketones from olefins and acetylenes using mercury compounds is a better method. For example, hydration of terminal acetylenes using HgSO gives methyl ketones cleanly. Oxymercuration of 1-olefins and subsequent oxidation with chromic oxide is... 

The phosphonium salt method works best with nucleophilic olefins [//, 12, 16, 17, 18, 19] (Table 1 and equations 1-3) and has been used m mechanistically important studies of difluorocarbene additions to norbornadienes [20 21, 22, 23] that provided the first example of a concerted homo-l,4-addition (equation 4) A recent modification uses catalytic 1,4,7,10,13,16 hexaoxacyclooctadecane (18-crown-6) to shorten reaction times and increase yields with less nucleophilic olefins [12] (Table 1) Neither procedure, however, compares with the use of phenyl(tri-f1uoromethyl)mercury or (trifluoromethyl)trimethyltin reagents [efficient reactions with less nucleophilic olefins (equations 3 and 5) and cyclic dienes [24, 25] (equations 6 and 7)... 

To generate chlorofluoro- and bromofluorocarbene, phenyl(dichlorofluoro methyl)- and phenyl(dibromofluoromethyl)mercury are vastly superior to other reagents [S, 14] High yields (>80%) of fluorohalocyclopropanes are typical, and even normally unreactive olefins can be used (equation 22)... 

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)... 

Seyferth (7) discovered that phenyl(trihalomethyl)mercury compounds decompose when heated in a solvent giving dihalocarbenes. When the solvent contains a suitable olefin, carbene addition occurs giving 1,1-dihalocyclopropane derivatives. The reaction has the advantage that strong base is not required in the reaction mixture, and base-... 

Monoalkylthallium(III) compounds can be prepared easily and rapidly by treatment of olefins with thallium(III) salts, i.e., oxythallation (66). In marked contrast to the analogous oxymercuration reaction (66), however, where treatment of olefins with mercury(II) salts results in formation of stable organomercurials, the monoalkylthallium(III) derivatives obtained from oxythallation are in the vast majority of cases spontaneously unstable, and cannot be isolated under the reaction conditions employed. Oxythallation adducts have been isolated on a number of occasions (61, 71,104,128), but the predominant reaction pathway which has been observed in oxythallation reactions is initial formation of an alkylthallium(III) derivative and subsequent rapid decomposition of this intermediate to give products derived by oxidation of the organic substrate and simultaneous reduction of the thallium from thallium(III) to thallium(I). The ease and rapidity with which these reactions occur have stimulated interest not only in the preparation and properties of monoalkylthallium(III) derivatives, but in the mechanism and stereochemistry of oxythallation, and in the development of specific synthetic organic transformations based on oxidation of unsaturated systems by thallium(III) salts. 

The reaction between Hg(II) and olefins has been examined from several angles and work prior to 1950 has been summarised by Chatt . Several types of complex and product are formed, depending on the olefin, which involve no change in the oxidation state of the mercury atom. Propenyl ethers have long been known to produce the corresponding glycol plus metallic mercury but no kinetics are available . 

The stereochemistry of electrochemical reduction of acetylenes is highly dependent upon the experimental conditions under which the electrolysis is carried out. Campbell and Young found many years ago that reduction of acetylenes in alcoholic sulfuric acid at a spongy nickel cathode produces cis-olefins in good yields 126>. It is very likely that this reduction involves a mechanism akin to catalytic hydrogenation, since the reduction does not take place at all at cathode substances, such as mercury, which are known to be poor hydrogenation catalysts. The reduction also probably involves the adsorbed acetylene as an intermediate, since olefins are not reduced at all under these conditions and since hydrogen evolution does not occur at the cathode until reduction of the acetylene is complete. Acetylenes may also be reduced to cis olefins in acidic media at a silver-palladium alloy cathode, 27>. 

The antidepressant protriptyline (116) causes skin photosensitization in man. Jones and Sharpies irradiated an aqueous solution of the hydrochloride with a medium-pressure mercury lamp for 16 h and separated the products by preparative TLC. First formed was the epoxide (117) which photohydrated to the diol (118). Also isolated was the enol (119) [84], Earlier, Gasparro and Kochevar had shown that only the hydrochloride was photodegraded under nitrogen in water or ethanol. Three products were isolated and all lysed erythrocytes, but the structure of only one was suggested. This was a cyclobutyl dimer as shown by its mass spectrum and its photolysis back to protriptyline by light of 254 nm. Presumably, a [2 + 2] cycloaddition of the olefine bonds had occurred [85]. 

The procedure described here allows for a convenient and efficient preparation in very high yields of large quantities of bromides from carboxylic acids containing an olefinic functionality. The Hunsdiecker reaction is traditionally accomplished by treating anhydrous silver carboxylates with bromine or iodine.2 Heavy metal salts such as mercury,3 lead,4 and thallium5 have also been used successfully as well as tert-butyl hypoiodite.6 The major disadvantages associated with the above methods, such as use of heavy metal salts and non-tolerance towards olefins, has led to the development of a more versatile method using O-acyl thiohydroxamates.7 8 The O-... 

Perlmutter used an oxymercuration/demercuration of a y-hydroxy alkene as the key transformation in an enantioselective synthesis of the C(8 ) epimeric smaller fragment of lb (and many more pamamycin homologs cf. Fig. 1) [36]. Preparation of substrate 164 for the crucial cyclization event commenced with silylation and reduction of hydroxy ester 158 (85-89% ee) [37] to give aldehyde 159, which was converted to alkenal 162 by (Z)-selective olefination with ylide 160 (dr=89 l 1) and another diisobutylaluminum hydride reduction (Scheme 22). An Oppolzer aldol reaction with boron enolate 163 then provided 164 as the major product. Upon successive treatment of 164 with mercury(II) acetate and sodium chloride, organomercurial compound 165 and a second minor diastereomer (dr=6 l) were formed, which could be easily separated. Reductive demercuration, hydrolytic cleavage of the chiral auxiliary, methyl ester formation, and desilylation eventually led to 166, the C(8 ) epimer of the... 

Chelate complexes could only be prepared in the case of platinum(II) as the metal ion, while the group V atom alone acted as a donor toward palladium(II) and mercury(II). The coordinated olefin in the chelate complexes was found to be readily displaced by monodentate ligands such as tertiary arsines, -toluidine and the thiocyanate ion. It was suggested by these workers that chelation would take place more readily if the olefinic phosphine or arsine were subject to greater steric restrictions than was the pentenyl ligand. 

Mercury(II) complexes of two t5T>es have been prepared (6) from pent-4-enyl diphenyl phosphine and mercuric halides. These complexes are of the formulae [LHgX2]2(X = Cl, Br, I) and LaHgXg (X = Br, I). In no case is the olefin coordinated to the metal. 

Kouwenhoven (6) sjmthesised two bis-olefinic ligands related to the simple pent-4-enyl compounds mentioned above. These were of the general formula PhD[(CH2)aCH =CH2]2 (D = P, As) and formed platinum(II) and mercury(II) complexes. The platinum complexes LPtCla (L = PhD[(CH2)3 CH=CH2]2) were found to be monomeric species containing, as shown by their i. r. spectra, one coordinated and one free double bond. The two mercury complexes [LHgClaJs did not contain coordinated olefinic groups. 

Zn(R-dtp)2 complexes have been characterized and their thermal stabilities investigated 173,184,190,297-299,301-305) Zn(R-dtp)2 compounds are thermally degraded to volatile olefins and non-volatile residues and this serves as the basis for gas chromatographic determination of the compounds 304,30s) Several papers describing pyrolyses of Zn(R-dtp>2 complexes have discussed mechanisms for formation of olefins, sulfides, and other products 173,184,190,298,299, 304) Dakternieks and Graddon i8s,283)35 mentioned earlier, have reported thermodynamic measurements for depolymerization and adduct formation reactions of zinc, cadmium and mercury R-dtp compounds. 

The compound is analyzed in aqueous phase by cold vapor-AA or ICP/AES method (See Mercury). It also may be derivatized with an olefin or benzene in alcohol to yield the corresponding mercuration product that may be identified from physical and spectral properties and elemental analysis. An ether or alcoholic solution of the compound may be analyzed by GC/MS. The characteristic masses should be 259, 257, 256, 202, and 200. 

The highly substituted derivative 186, in the form of the potassium salt, has been recommended for use in detonators in place of the more dangerous mercury fulminate. l,2,3-Benzotriazine-4-thione (39, R — H) has been used in photographic transfer emulsions as an inhibitor and toning agent, and heavy metal salts of the oxygen analog 10, R = H are employed as photodevelopable emulsions. The latter compound is also claimed to be useful as a stabilizer in olefin polymers and as an antioxidant in certain other polymers. Dimeric derivatives of 10 have... 

---