Thallium Tristrifluoroacetate

Taylor and co-workers have shown that nonphenolic oxidative coupling of A -methyltetrahydrobenzylisoquinolines can be performed in good to excellent yield using TTFA. Thus treatment of the tetrahydrobenzyliso-quinoline 29a with XTFA at —40° led to a 467 yield of ocoteine.  

Attempted coupling of 29a with thallium(IIl) acetate at 0° in the same solvent mixture surprisingly led to 8-acetoxyocoteine.  

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The latter was transformed to dysazecine (114) by the usual three-step procedure (81) (Scheme 34). Other synthetic routes to dibenz[d,/]azecines have been reported. Oxidative coupling of tetramethoxy derivative 120 promoted by thallium tristrifluoroacetate (TTFA) gives an excellent yield of 121 (41) (Scheme 35). A biogenetic type approach to dibenz[rf,/]azecines has been de-... 

Recent patents cover the conversion of both isomers of salutaridinol (148 R = Me) into thebaine in 80% yield by the action of thionyl chloride, phosphorus pentachloride, or other acid chlorides, followed by decomposition with bases.180,181 N-Acyl-nor-reticulines have been cyclized by thallium tristrifluoroacetate to the iV-acyl-norsalutaridines [149 R = Ac, F3CCO, cyclo-C3H5CO, EtOCO, or PhCH2OCO), which have been reduced to the corresponding salutaridinols (148) these have been cyclized by sodium hydroxide to the related acyl-northebaines.182... 

A number of intramolecular variations are documented, some of biogenetic interest. The benzophe-none (224) was cyclized in good yield (83%) to 2,6-dihydroxyxanthone (225) with ferricyanide," and the synthetic depside (226) yielded diploicin (227) on manganese dioxide oxidation." Finally the di-a lheptanoid (228) afforded the macrocyclic ether (229) on reaction with thallium tristrifluoroacetate similar ethers, e.g. acerogenin, occur naturally. ... 

Intramolecular Cp—Car couplings have been observed in the anodic oxidation of a series of 4-hy-droxy-2-vinylbiphenyls, e.g. 293), which afforded the corresponding spirodienones (c.g. 294 92% from 293). Another Cp—Car linkage resulted from the brief oxidation of the dihydrocinnamyl cinna-mate (295) with thallium tristrifluoroacetate-catalytic boron trifluoride (water-quench), when the eight-membered lactone (296) was formed. ... 

Schwartz successfully emulated the in vivo para-ortho coupling of N-acylnorreticuline derivatives by the use of thallium tristrifluoroacetate (TibA), Scheme 9. Treatment of ethoxycarbonyl derivative 91 with one equivalent of the salt afforded a... 

In order to imitate nature in the synthesis it is necessary first to realize a ortho—para coupling of reticuline to yield salutaridine (43a). The authors succeeded in that respect by application of a thallium tristrifluoroacetate coupling method at —78° for 3 hr and then at -20° for 12 hr (493). During... 

Yields in the above reactions can often be improved by the addition of 1 mole of triphenylphosphine directly to the trifluoroacetic acid solution of the reactants immediately before final work-up. It would appear that the triphenylphosphine functions as a scavenger for TTFA released in the metal-metal exchange reaction, thus protecting the final phenol from further electrophilic thallation and/or oxidation. Validation of the metal-metal exchange mechanism was obtained indirectly by isolation and characterization of an ArTlX2/LTTFA complex directly from the reaction mixture. NMR analysis revealed that this complex still possessed an intact aryl-thallium bond, indicating that it was probably the precursor to the transmetallation products, an aryllead tristrifluoroacetate and TTFA. 

Iodine(III) tnfluoroacetates (iodine tristrifluoroacetate and lodosobenzene bis-trifluoroacetate) resemble lead(IV), thallium(III) and mercury(II) reagents in their reactions but do not share the undesirable high toxicity typical for the heavy metals Iodine tristrifluoroacetate is a very powerful oxidant that can introduce the trifluoroacetoxy group even into alkanes [60 61] Because branched alkanes react ... 

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