Mercury catalysed hydrolysis

Reagent (12) was used for synthon (10), though no doubt bromoacetone would also add to the enamine ol (11). Mercury catalysed hydrolysis oJ vinyl chloride released (9) which duly cyclised to (8) in base. Synthesis ... 

Both of these transformations deserve comment. Dithianes are rather more stable than acetals, and a mercury reagent has to be used to assist their hydrolysis. Mercury(ll) and sulfides form strong Thiols are also known as mercaptans coordination complexes, and the mercury catalyses the reaction by acting as a sulfur-selective Lewis acid. 

Vinyl azides, which can be obtained from olefins, are converted in high yield into the corresponding carbonyl compounds by sodium sulphide in methanol." The mercury(ii)-catalysed hydrolysis of the vinyl chloride (32) shows an interesting solvent dependence in dichloromethane, acetic acid, benzene, or acetonitrile the yield of (33) is almost quantitative and no trace of (34) is observed, whereas in methanol 83% (34) and 6% (33) are obtained [equation (7)]." ... 

The acid-catalysed hydrolysis of thioimidate esters, R C(SR )=NR , is promoted " by mercury(ii), and [AUCI4]- has been foundto promote the hydrolysis of N-cyclohexylmethylthiobenzimidate PhC(SMe)=NC6Hn. Co-ordination of the metal cation to the sulphur is probably involved. 

This reaction is widely utilised in organic synthesis, when carbonyl groups may be protected as the thioacetals or thioketals. Unlike acetals or ketals, the thio compounds do not undergo acid catalysed hydration, and may be used in acidic reaction conditions. The metal-directed hydrolysis is rationalised in terms of the soft-soft interaction of the sulfur with the metal cation, in contrast to the hard-soft interaction with a proton. Hydrolysis is readily achieved on treatment with aqueous mercury(n) or silver(i) salts. Once again, the... 

The anthracyciinone class of anticancer compounds (which includes daunomycin and adriamycin) can be made using a mercury (I I )-promoted alkyne hydration. You saw the synthesis of alkynes in this class on Chapter 9 where we discussed additions of metallated alkynes to ketones. Here is the final step in a synthesis of the anticancer compound deoxydaunomycinone the alkyne is hydrated using Hg2+ in dilute sulfuric acid the sulfuric acid also catalyses the hydrolysis of the phenolic acetate to give the final product. 

Hydrolysis of complexes of the type MFe is catalysed not only by acid but also by a series of metal ions. Kinetic data have been obtained for catalysis of hydrolysis of PFe, AsFg", AsFgCOH)- and also of BF4-, by beryllium(ii), aluminium(iii), zirconium(iv), and thorium(rv). Again this may be seen as an extension of studies on cation catalysis of hydrolysis of transition-metal complexes, e.g. the numerous studies of mercury(ii)-catalysed aquations of cobalt(iii)-ammine-halide complexes, or the recent study of metal ion catalysis of chloro(ethylenediaminetriacetato)-cobaltate(m). ... 

Methoxy-l-phenylthioprop-l-ene is alkylated exclusively at the position a- to the sulphur atom via the lithio-derivative a/3-unsaturated aldehydes are formed on subsequent hydrolysis catalysed by mercury(II) chloride (Scheme 55). ... 

Grunwald-Winstein analyses of kinetic results have proved less successful for the two-stage mercury(ii)-catalysed aquation of the [RuCl(NH3)6] + cation, for associative attack of cyanide at the [Fe(bipy)a] cation, and for aquation of the [Fe(phen)a] + cation. Logarithms of rates of isomerization of trans-[Cr(ox) -(0112)2] correlate better with logarithms of rates of base hydrolysis of ethylene chlorohydrin than with solvent Y values (i.e. than with logarithms of rates of t-butyl chloride solvolysis). ... 

Interest continues in the effects of micellar agents on rates of inorganic reactions. Aquation of oxalato-cobalt(m) and -chromium(iii) complexes is mentioned in a review of reversed micellar systems predicted and actual rates have been compared for a variety of reactions, including the mercury(n)-catalysed aquation of [CoX(NH3)g] + cations. Micellar effects on uncatalysed aquation of cis- and of tra j -[CoCl2(en)2]+ are small (as expected) but real. Other reactions for which the kinetic consequences of micelle or polyelectrolyte addition have been d cribed include complex formation from nickel(ii), the conversion of ammonium cyanate into urea, and the hydrolysis of pyrophosphate. ... 

The faster mercury(n)-catalysed aquation of /ra 5-[Co(ete)Cl2l+ proceeds with retention of configuration as expected. Base hydrolysis is significantly slower than for the corresponding 2,3,2-tet complex, in line with the absence of the secondary amine groups which are known to be primarily involved in conjugate-base formation from the [Co(2,3,2-tet)Cl2] ion. 

Lithium tetrafluoroborate in wet acetonitrile has been described as an effective combination for the hydrolysis of acetals under mild weakly acidic conditions. Dithians were unaffected. Methods for the hydrolysis of thioacetals continue to appear. Reagents that have been described include a polystyryl-mercury(n) trifluoroacetate combination, which retains the metal on the resin, lead(iv) dioxide and boron trifluoride etherate, aqueous hydrochloric acid in dioxan containing dimethyl sulphoxide, methyl-bis(methylthio)sulphonium hexa-chloroantimonate, and iodoxybenzene, catalysed by toluene-p-sulphonic acid. Dithioacetals derived from ethane-1,2-dithiol may be cleaved with dimethyl sulphoxide in combination with either t-butyl or trimethylsilyl bromides and iodides. Regeneration of ketones from ethanediyl-S S -acetals via the lithium-di-isopropylamide-promoted fragmentation to the thioketone and subsequent hydrolytic work-up only gives satisfactory yields for aryl methylketone derivatives. Dithioacetal SS-dioxides are rapidly cleaved in hot methanolic hydrochloric acid solution. ... 

For RCN = benzonitrile or 3- or 4-cyanophenol, this hydrolysis in aqueous solution is first-order in hydroxide-ion concentration. The rate enhancement due to the co-ordinated [Co(NHs)6] + moiety is ca. 10 times. The kinetic parameters for hydrolysis of these co-ordinated nitriles are listed in Table 2. A much greater rate enhancement, this time of at least 10 times, is reported for the mercury(n)-catalysed hy olyses of [Co(en)2 H2N(CH2) CN Br] +, where n = 1 or 2. The rates are first-order in mercury(n) concentration, but... 

The most spectacular effects of salts on reaction rates are observed in micellar solutions. For instance the presence of anionic surfactants such as dodecyl or tetradecyl sulphate accelerates rates of mercury(n)-catalysed aquation of [CoCNHalsCl] by several orders of magnitude, and polyethylene or polystyrene sulphonates have a similar effect on mercury(n), thallium(m), and silver(i) catalyses of the aquation of the [CoCNHalsBr] cation. Cationic surfactants such as the octylammonium or dodecyl-ammonium ions have a dramatic effect on rates of aquation of the [Cr(ox)3] " anion. Both anionic and cationic surfactants catalyse the (associative) hydrolysis of the Lewis acid-base adduct EtgN.SOs. ... 

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