Thallium tris-

Thallation of aromatic compounds with thallium tris(trifluoroacetate) proceeds more easily than mercuration. Transmetallation of organothallium compounds with Pd(II) is used for synthetic purposes. The reaction of alkenes with arylthallium compounds in the presence of Pd(Il) salt gives styrene derivatives (433). The reaction can be made catalytic by use of CuCl7[393,394], The aryla-tion of methyl vinyl ketone was carried out with the arylthallium compound 434[395]. The /9-alkoxythallium compound 435, obtained by oxythallation of styrene, is converted into acetophenone by the treatment with PdCh[396]. 

Thallium tris(3-mesitylpyrazol-l-yl)borate and [(j -cod)2RhCl] produce [(ry -TpORhfjj -cod)] (93IC3471). These complexes appeared to be good catalysts... 

Biaryl phenol coupling.1 The natural dibenzylbutanolide lignans, prestegane A (la) and B (lb), are converted to the corresponding bisbenzocyclooctadiene lactones (2) by oxidation with Ru02 in TFA-TFAA in 80-85% yield. The usual reagent for this oxidation, thallium tris(trifluoroacetate), is less efficient (45-50% yields). 

Method C A solution of 0.5 mmol of (2/ /S,3R/S)-2,3-dialkyl-l,4-diarylbutane and 0.125 mL (1 mmol) of boron trifluoride-diethyl ether complex in 2mL of CH2C12 is added to a stirred suspension of 0.36 g (0.65 mmol) of thallium tris(trifluoroacctatc) in 10 mL of CH2C12 under argon. The mixture is stirred until the end of the reaction and then diluted with ethyl acetate and worked up as in method A. 

Thallium Tris-fpcnntfluoro-phenyl]-XITI/4, 371 (Ar- MsiX + T1C1,)... 

Thallation of aromatic compounds with thallium tris(trifluoroacetate) proceeds more readily than mer-curation and in many instances more selectively. Ortho derivatives are obtained frequendy when functional groups with unshared electron pairs are present to direct the metallation.39... 

Thallium 2,4,6-tris(dioxoselena)hexahydrotriazine-l,3-5-triide ( Thallium tri-selenimidate )... 

The norbelladine derivative 408, which served as the starting material for the synthesis of ( )-oxocrinine (415) (Scheme 35), may be readily prepared from the reductive animation of piperonal with tyramine followed by acylation with trifluoroacetic anhydride (191,192). When the N-acylated monophenol 408 was treated with excess thallium tris(trifluoroacetate) in methylene chloride, the di-enone 412 was obtained in 19% yield (191), whereas use of the oxidant vanadium oxyfluoride in trifluoroacetic acid/trifluoroacetic anhydride afforded 412 in 88% yield (192). Base-induced N-deacylation of 412 was accompanied by spontaneous cyclization to furnish racemic oxocrinine (415). Attempts to oxidize the free amine derived from 408 led to the formation of a number of products, some of which resulted from oxidation at nitrogen. 

T1I3 thallium tris(iodide), or thallium(III) iodide,... 

Some effected the coupling of phenyl-, 2-fuiyl-. and 1-hexenylboronic acids with 4-thallated indole-3-carboxaldehyde (Pd(OAc),/DMF) to give 4-substituted 3-formylin-doles [148]. Regioselective thallation of indole-3-carboxaldehyde is achieved using thallium tris-trifluoroacetate in 77% yield. Indole 129, which is available by the Buchwald zirconium indoline synthesis, was used by Buchwald to synthesize 130 via a Suzuki protocol [149]. Boronate ester 130 is prepared by the hydroboration of3-methyl-1-butyne with catechol borane. Indole 131 had been used in earlier studies to synthesize the clavicipitic acids. 

Arylthallium(in) compounds (83) are generally prepared by electrophilic aromatic thallation with thallium tris(trifiuoroacetate) (84). 

The formation of iodobenzene by treatment of phenylthallium(III) compounds with potassium iodide was reported, without experimental details, by Challenger et al in the 1930 s. 2,113 jhe potential and synthetic interest of this iododethallation reaction was extensively studied by McKillop and Taylor in the early 1970 s.8 7-89 Although arylthallium(III) compounds prepared by reaction of the arenes with thallium tris(trifluoroacetate) (84) can be isolated, they can also be directly converted into aryl iodides by addition of aqueous potassium iodide to the thallation reaction mixture. An intermediate arylthallium(III) diiodide (91) was suggested to be formed and to decompose intramolecularly to lead to the aryl iodide. ... 

Thallation of benzanilides with thallium tris(trifluoroacetate) in a mixture of trifluoroacetic acid and ether gave the c rr/to-thallated products. Reaction of these products with copper(I) acetylide in acetonitrile led to the 2-benzamidotolanes (119), which were eventually elaborated into the 2-phenyl-indole derivatives. 111 ... 

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