Mercury trifluoroacetates synthesis

The popular approach to tetrahydrofurans involves an electrophilic process and the commonly used electrophiles for the cyclization are acids, oxygen, halogen, mercury (see Section 3.11.2.2.9) and selenium. The ionic hydrogenation of furans with excess triethyl-silane in trifluoroacetic acid affords high yields, e.g. 2-methylfuran is reduced to 2-methyl-tetrahydrofuran and 2-ethylfuran to 2-ethyltetrahydrofuran (see Section 3.11.2.5). The synthesis of several dihydro and tetrahydrofurans containing natural products by chirality transfer from carbohydrates has been used successfully for total synthesis, e.g. (-)-nonactic acid. A reasonable yield of 2-alkyltetrahydrofuran was prepared from 4-alkylbut-l-en-4-ol by hydroboration followed by cyclization with p-toluenesulfonic acid. 

Strong acidolytic conditions were precluded by the presence of an N-Boc group and an activated secondary benzylic alcohol in a synthesis of the Ecteinasddin fragment depicted in Scheme 5.7. Hence, the S-p-methoxybenzyl group was excised with mercury(II) trifluoroacetate in acetic acid and the liberated thiol then cydised onto a benzylic centre under the aegis of trifiuoroacetic acid.20 21... 

Cyclization. Treatment of the unsaturated enol phosphate ester 1 with 1 equiv. of mercury(II) trifluoroacetate in nitromethane at 0° followed by aqueous sodium chloride produced the mercurated bicyclic keto ester 2 in 60% yield along with 20% of the monocarbocyclic product 3. Keto ester 2 is an intermediate in a total synthesis of aphidicolin (4). This reaction is the first example of the use of a mercury(II) salt tor simultaneous construction of two carbocyclic rings. ... 

Chiral synthesis of a prostanoid.Trost etal. have devised an enantioconvergent prostanoid synthesis from 1, in which a 1,3-hydroxy shift interconverts the two enantiomers. The interconversion was possible by equilibration of the urethane of 1 with (S)-l-o -naphthylethylamine catalyzed with mercury(II) trifluoroacetate (7, 382). At equilibrium the ratio of 2a/2b is about 1 3. By separation and repeated... 

Mercury(II) trifluoroacetate finds frequent employment in organic synthesis 223, 229, 230) since it adds rapidly, stereospecifically, and quantitatively across nonconjugated olefinic bonds, for example, Eq. (21). The mercurated products thus prepared may be readily converted... 

During the total synthesis of (+)-fredericamycin A, the spiro 1,3-dione center was introduced by R.D. Bach et al. utilizing a mild mercury-mediated semipinacol rearrangement that involved a [1,2]-acy shift. The indanone dithioacetal was reacted with 1,2-b/s[(trimethylsilyl)oxy]cyclobut-1-ene in the presence of mercuric trifluoroacetate and the rearrangement took place in situ. 

In a final example specifically devoted to the use of mercury reagents following Wittig olefinations, Qiao, et al.,6 utilized mercuric trifluoroacetate to effect ring closure. This example, shown in Scheme 7.1.6, was utilized in the synthesis of the C-phosphonate disaccharide, shown in Figure 7.1.1, as a potential inhibitor of peptidoglycan polymerization by transglycosylase. 

Mercuric trifluoroacetate [Hg(OCOCF3)2] is an effective reagent for the cyclization of hydroxy thio-esters. 5 This cyclization procedure was used by Masamune et al. for the conversion of 225 to 227 (in 90% yield) in a synthesis of zearalenone dimethyl ether. Masamune developed this procedure to complete the total synthesis of methymycin, where one step involved treatment of a thioester with mercuric salts. 2,96 Mercury(II) has an affinity for bivalent sulfur and it binds the thioester unit as well as the terminal hydroxyl... 

Synthesis of esters and lactones (6, 581-582). Masamune et alf have reported further studies on the synthesis of esters by the reaction of a 2-methylpropane-2-thioester with an alcohol by activation of 1 with a metal salt (equation I). Originally mercury(II) trifluoroacetate and mercury(II) methanesulfonate were... 

High yield intramolecular acylation reactions at the 2-position of an appropriately substituted furan thiol ester has been used in natural product synthesis. Model cyclization reactions were carried out using mercury(II) trifluoroacetate <90TL1977>. However, in the step shown in Equation (7), which... 

A synthesis of the insecticidal compound allosamidine (plus isomer) and aglycone allosamizoline has been reported. The key step in the formation of the allosamizoline involved the oxyamination of cyclopentene 71 with osmium tetroxide and sodio ethyl A -chlorocarbonate in the presence of mercury(U) trifluoroacetate to afford 72 together with regioisomers. See also Chapter 19 for other syntheses of allosamizoline. 

The initial studies on the capacity of the mercurial PhHg-CF, to act as a CFj-transfer reagent were carried out with material obtained by fluorination of the chloro- or, preferably, bromo-analogue [PhHg CX, (X = Cl or Br, respectively)] with PhHgF-HF. - A better synthesis has been developed recently this involves the preparation of trifluoromethylmercuric bromide starting from trifluoroacetic acid and mercuric oxide (see above) and then a... 

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