Mercury trifluoroacetate

Similar methods to effect lactonization have been proposed by Corey et al.7 and Masamune et al,8 The first consists of prolonged heating of hydroxy-S-( 2-pyridyl)carbothioates in boiling xylene the second is the mercury trifluoroacetate-promoted cyclization of a hydroxy-S-tert-butyl carbothloate. 

Under these conditions, hydrolysis of peracetylated derivatives 135,136, and 139 was very slow, presumably because of the electron-withdrawing effect of the acetoxy groups. When /V-iodosuccinimide was employed instead of mercury trifluoroacetate, the reaction was complete in 12 h at room temperature and the yield was good (Table II). 

Conversion of synthetic picrotoxinin (1) to picrotin (2) was achieved by Corey and Pearce in four steps and 30% overall yield 124). To prevent intramolecular oxymercuration, the tertiary alcohol of picrotoxinin (1) was protected as trifluor-oacetate 346 prior to addition of mercury trifluoroacetate in a benzene/THF mixture as solvent. Demercuration with sodium borohydride failed, thus the covalent C-Hg bond was cleaved by tributylstannane in ethanol. Mild hydrolysis of the bistrifluor-oacetate 347 afforded picrotin (2) in 30% overall yield (75% corrected for recovered 1) from picrotoxinin (1). 

Oxymercuration of simple alkyl- and acyl-substituted cyclopropenes generally results in ring opening.Addition of mercury(II) acetate to 3-methyl-3-phenylcyclopropene, however, gave a low yield of a cyclopropane containing organomercury compound (15-20%), which was converted into an isomeric mixture of 1 -methoxy-2-methyl-2-phenylcyclopropanes by reduction with lithium aluminum hydride. Reaction of 5 with mercury trifluoroacetate in methanol and then sodium hydroxide led predominantly to one cylopropane. ... 

Bis(trifluoromethyl)mercury is useful in the preparation of numerous CF3 derivatives, especially of group IV elements. It was first prepared in 1949 by irradiation of CF3I and Hg in the presence of Cd. Alternative routes include radiofrequency discharge methods, for example, reaction of CF3 radicals witli HgXz or elemental mercury. Preparative scale quantities are best obtained by decarboxylation of mercury trifluoroacetate in the presence of carbonate. ... 

In studying the reaction between pentamethylbenzene and mercury trifluoroacetate in CF3COOH by UV- and PMR spectroscopy indications were obtained of an equilibrium mixture of the ions (26) and (27)... 

A more modern way is the mercury trifluoroacetate-induced cychsation according to Noyori. The starting material is obtainable from a three-component coupling reaction. The stereospecific cyclisation proceeds via a mercurinium ion in what amounts to a 5-exo-di -cyclisation. Critical for the ( /Z)-isomer ratio is the subsequent mercury cleavage. Normally, this reaction proceeds radically with loss of stereochemical integrity. However, if the mercury residue is removed reductively in protic solvents, then the stereochemistry is preserved. 

Ruthenium tetroxide Silver sulfide Mercury trifluoroacetate... 

For the Fleming-Tamao step, we developed a novel procedure to avoid side-reactions during the scale-up. We found that the oxidation could be performed in presence of mercury trifluoroacetate, " to give alcohol 3 in 76% yield (based on recovered starting material). 

The electrophilicity of Hg(II) is drastically enhanced by using mercury trifluoroacetate Hg(TFA)2 instead of Hg(OAc)2, and CF3CO2H as the solvent which is more ionizing than CH3CO2H in order to favor the formation of the Wheland intermediate (above, a complex). This results in mercuration that is 7 x 10 times faster with Hg(TFA)2 than with Hg(OAc)2, so that five mercurations of benzene become possible whereas only one is possible, with Hg(OAc)2 ... 

Ph -Ph- ruthenium tetroxide silver sulphide mercury trifluoroacetate... 

Aromatics Aromatics Aromatic polyamides Polyphenylene oxide Ruthenium tetroxide Silver sulfide Mercury trifluoroacetate... 

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