Mercuric reaction + olefins

Pd(II) compounds coordinate to alkenes to form rr-complexes. Roughly, a decrease in the electron density of alkenes by coordination to electrophilic Pd(II) permits attack by various nucleophiles on the coordinated alkenes. In contrast, electrophilic attack is commonly observed with uncomplexed alkenes. The attack of nucleophiles with concomitant formation of a carbon-palladium r-bond 1 is called the palladation of alkenes. This reaction is similar to the mercuration reaction. However, unlike the mercuration products, which are stable and isolable, the product 1 of the palladation is usually unstable and undergoes rapid decomposition. The palladation reaction is followed by two reactions. The elimination of H—Pd—Cl from 1 to form vinyl compounds 2 is one reaction path, resulting in nucleophilic substitution of the olefinic proton. When the displacement of the Pd in 1 with another nucleophile takes place, the nucleophilic addition of alkenes occurs to give 3. Depending on the reactants and conditions, either nucleophilic substitution of alkenes or nucleophilic addition to alkenes takes place. 

T n the search for new synthetic uses of organomercurials and the olefin A mercuration reactions in general, attention was drawn to ozone as a possible reactant. 

In the previous edition of EIC, Larock described in detail the hydro-, aUcoxo-, peroxo-, and acyloxy-mercuration of olefins. These reactions generally proceed in a Markovnikov fashion yielding products of anti addition, although in some cases (e.g. 

Hofmann-Sand reaction. Olefin mercuration with mercuric salts (halides, acetates, nitrates, or sulfates) in aqueous solution. In alcoholic solutions, the accelerated reaction produces alkoxylalkyl compounds. 

Electrophilic additions also occur to cumulated dienes (allenes). Caserio and co-workers established that the mechanisms of both the oxy-mercuration reaction and the electrophilic addition of bromine to allenes are similar to the corresponding additions to olefins. The oxymercuration of ( )-(—)-2,3-pentadiene (82) in methanol produced 83% of (S)-traMS-3-acetoxy-mercuri-4-methoxy-2-pentene (83), confirming the anti pathway for the addition. Also formed was 17% of cis-3-acetoxymercuri-4-methoxy-2-pentene (84), which was presumed to have the R configuration. As shown in Figure 9.48, the product ratios can be explained on the basis of preequilibrium formation of mercurinium ions resulting from attachment of mercury to either the top or the bottom of one of the double bonds. Subsequent rate-limiting attack of methanol on the mercurinium ions is easier for the pathway... 

Zinc carboxylates are prepared in aqueous ethanol solution by sonication of zinc carbonate in the presence of the acid.1 2 Only 5-min irradiation times are required, and the method was successfully applied to Boc-protected amino acids (p. 147). Mercuric carboxylates were prepared from yellow mercuric oxide and carboxylic acids.43 The sonochemical reaction proceeds very fast in apolar solvents, and a series of salts were prepared by this method and used in hydroxy-mercuration reactions. This reaction can be effected directly from a mixture of the olefin, mercuric oxide, and a carboxylic acid (p. 119). 

Reviews.—Recent reviews involving olefin chemistry include olefin reactions catalysed by transition-metal compounds, transition-metal complexes of olefins and acetylenes, transition-metal-catalysed homogeneous olefin disproportionation, rhodium(i)-catalysed isomerization of linear butenes, catalytic olefin disproportionation, the syn and anti steric course in bi-molecular olefin-forming eliminations, isotope-elfect studies of elimination reactions, chloro-olefinannelation, Friedel-Crafts acylation of alkenes, diene synthesis by boronate fragmentation, reaction of electron-rich olefins with proton-active compounds, stereoselectivity of carbene intermediates in cycloaddition to olefins, hydrocarbon separations using silver(i) systems, oxidation of olefins with mercuric salts, olefin oxidation and related reactions with Group VIII noble-metal compounds, epoxidation of olefins... 

The aHphatic iodine derivatives are usually prepared by reaction of an alcohol with hydroiodic acid or phosphoms trHodide by reaction of iodine, an alcohol, and red phosphoms addition of iodine monochloride, monobromide, or iodine to an olefin replacement reaction by heating the chlorine or bromine compound with an alkaH iodide ia a suitable solvent and the reaction of triphenyl phosphite with methyl iodide and an alcohol. The aromatic iodine derivatives are prepared by reacting iodine and the aromatic system with oxidising agents such as nitric acid, filming sulfuric acid, or mercuric oxide. 

The olefin of the Voc group is very susceptible to electrophilic reagents and thus is readily cleaved by reaction with bromine or mercuric acetate. 

Alkyl fluorides have been prepared by reaction between elementary fluorine and the paraffins, by the addition of hydrogen fluoride to olefins, by the reaction of alkyl halides with mercurous fluoride, with mercuric fluoride, with silver fluoride, or with potassium fluoride under pressure. The procedure used is based on that of Hoffmann involving interaction at atmospheric pressure of anhydrous potassium fluoride with an alkyl halide in the presence of ethylene glycol as a solvent for the inorganic fluoride a small amount of olefin accompanies the alkyl fluoride produced and is readily removed by treatment with bromine-potassium bromide solution. Methods for the preparation of alkyl monofluorides have been reviewed. ... 

The acid catalyzed hydration of olefins is frequently attended by decomposition or rearrangement of the acid-sensitive substrate. A simple and mild procedure for the Markovnikov hydration of double bonds has recently been devised by Brown and co-workers 13). This reaction, which appears to be remarkably free of rearrangements, initially involves the addition of mercuric acetate to the double bond to give the 1,2-... 

Alkyl mercuric hydrides are generated in situ by reduction of an alkyl mercuric salt with sodium borohydridc (Scheme 3.91). Their use as radical traps was first reported by Hill and Whitesides491 and developed for the study of radical-olefin reactions by Giese,489490 Tirrell492 and coworkers. Careful choice of reagents and conditions provides excellent yields of adducts of nucleophilic radicals (e.g. -hexyl, cyclohexyl, /-butyl, alkoxyalkyl) to electron-deficient monomers (e.g. acrylics). 

Reaction of the environment with the starting material The commonest example of this type of interaction is the protonation of the substrate by acids in the electrolysis medium, but pH effects will be dealt with in a later section. There are, however, other chemical interactions which can occur. For example, the mechanism and products of the oxidation of olefins are changed by the addition of mercuric ion to the electrolysis medium. In its absence, propylene is oxidized to the allyl cation (Clark et al., 1972),... 

We are currently trying to answer specifically the question of whether ir-bonded complexes do occur in certain cases where insertion reactions are observed. I think they do because I believe that the same factors which favor stabilization of this type of transition state will also tend to favor formation of 7r-bonded olefin complexes, which are only slightly removed from this. At the moment Bern Tinker is examining the insertion of olefins in mercuric complexes to see whether there is any indication of 7r-bonded intermediates. In his paper, Dr. Heck referred to some unpublished work relevant to this theme. I would certainly be interested in anything more he can tell us about that. 

Olefins may be converted to primary amines by the Ritter reaction10 or by reaction with mercuric nitrate in acetonitrile solution.11 In both cases regiospecificity for the formal addition of ammonia across the double bond is opposite to that observed in the hydroboration-amination sequence. 

Olefins of the form RCH=CHR and RR C=CH2 add to nitriles in the presence of mercuric nitrate to give, after treatment with NaBH4, the same amides that would be obtained by the Ritter reaction.740 This method has the advantage of avoiding strong acids. 

Sometimes a yellow color (mercuric oxide) appears at this point and disappears as the reaction proceeds. If the yellow color does not disappear in about 10 minutes, 1.5 ml. of 70% perchloric acid per mole of mercuric acetate may be added to accelerate the reaction. Under these conditions even unreactive olefins are completely oxymercurated in about an hour. 

Oxymercuration of alkenes is an electrophilic reaction involving the addition of mercuric salt and of a protic solvent (alcohols) according to reaction 9. UV/VIS spectrophotometric investigation of the olefin/mercuric salt reaction mixtures in methylene chloride provides evidence of the presence of an electron donor-acceptor complex between olefin and mercuric salt110 which is considered to be on the reaction pathway of the oxymercuration. 

Fluoroolefins add mercuric fluoride at 50- 100 °C to give bis(polyfluoroalkyl)-mercury derivatives. Reaction is usually carried out in hydrogen fluoride as a solvent. This process was reviewed and the electrophilic nature of this process established [6]. Addition to olefin starts by the attack of cation 3 (Eq. 5) on the double bond of fluoroolefin. 

Cupric acetate does not function as a reoxidant at the low temperature generally useful for the olefin arylation reaction. Mercuric acetate is sometimes useful but it may add to the olefins present and complicate the reaction. Lead tetracetate reoxidizes palladium but also causes the formation of acetates by a reaction apparently analogous to the cupric... 

Several papers on the chemistry of longifolene derivatives have been published. These include the conversion of the two half-esters (225) and (226) into the same olefinic ester (227) with Pb(OAc)4-Cu(OAc)2, the reaction of longifolene (228) with mercuric acetate followed by iodine chloride to give (229) and (230), and the reaction of longicyclene (231) with bromine in pyridine and iodine chloride-pyridine complex in acetic acid to yield (232) and (233) respectively. 

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