From arylthallium

Aryl iodides and fluorides can be prepared from arylthallium bis(trifluor-oacetates) (see 12-21), indirectly achieving the conversions ArH —> Arl and ArH ArF. The bis(trifluoroacetates) react with KI to give Arl in high yields. Aryllead triacetates, ArPb(OAc)3, can be converted to aryl fluorides by treatment with BFs-etherate. ... 

This phenol synthesis complements the analogous reaction (see below) from arylthallium ditrifluoroacetates (147). Although yields are only moderate, the procedure represents a viable conversion of aryl Grignard reagents to phenols. It is a practical method, however, only when the diarylthallium trifluoroacetate precursor is formed via the Grignard route the alternative synthesis via symmetrization of arylthallium ditrifluoroacetates is obviously circuitous, since the latter compounds may be converted directly to phenols. 

Irradiation/potassium thiocyanate Ar. thiocyanates from arylthallium bis(trifluoroacetates) s. 27, 888 tttIKSCN ArTKOCOCFjts ArSCN... 

Arylthallium bis(trifluoroacetates) (see 12-21) can be converted to aryl nitriles by treatment with copper(I) cyanide in acetonitrile. Another procedure uses excess aqueous KCN followed by photolysis of the resulting complex ion ArTl(CN)3 in the presence of excess KCN. Alternatively, arylthallium acetates react with Cu(CN)2 or CuCN to give aryl nitriles. Yields from this procedure are variable, ranging from almost nothing to 90 or 100%. 

Specifically, it has recently been found 149) that diarylthallium tri-fluoroacetates may be converted into aromatic iodides by refluxing a solution in benzene with an excess of molecular iodine. Yields are excellent (74-94%) and the overall conversion represents, in effect, a procedure for the conversion of aromatic chlorides or bromides into aromatic iodides via intermediate Grignard reagents. The overall stoichiometry for this conversion is represented in Eq. (10), and it would appear that the initial reaction is probably formation of 1 mole of aromatic iodide and 1 mole of arylthallium trifluoroacetate iodide [Eq. (8)] which subsequently spontaneously decomposes to give a second mole of aromatic iodide and thallium(I) trifluoroacetate [Eq. (9)]. Support for this interpretation comes from the... 

When the reaction of the arylthallium compound ArTlX2 with the nucleophile Nu" leads to a too stable intermediate AtT1Nu2, competing protonolysis may become predominant. This is circumvented by using copper salts, which favours the removal of a ligand from the thallium metal. According to Uemura et al, this reaction leads to substitution in a concerted process by reductive displacement of... 

A different mechanism was suggested by McKillop and Taylor, who considered that the copper mediated reactions involve single electron transfer from the copper Cu(I) species to the thallium substrate. The arylthallium(II) species loses a thallium(I) salt and the aryl radical. This aryl radical secondarily reacts with the copper(II) species formed in the first step by electron transfer. 5,106... 

Other monovinylthallium(ni) compounds such as (132), the product of oxythallation of acetylenes, react analogously to the arylthallium compounds. Halogenodethallation and pseudohalogeno-dethallation reactions result from the interaction of the oxyalkenylthallium compound with either potassium iodide or with the appropriate copper derivatives. 6... 

Thallation of species deactivated to electrophilic substitution requires more vigorous conditions, but Tl(III) trifluoroacetate decomposes above 100°C. The thallating ability of Tl(III) trifluoroacetate can be improved by the addition of electron-pair acceptor acids, such as BFj or SbFj. Another approach is the use of the even more powerful thallating agent, Tl(III) trifluoromethanesulfonate, formed from Tl(III) oxide and trifluoromethane sulfonic acid. It reacts with even unreactive polyfluoroarenes to produce arylthallium bis(trifluoromethanesulfonate) ° ... 

Easier and faster is reaction of arylthallium bis(trifluoroacetate) in the presence of trimethylphosphite. A rapid, exotherm results, yielding 65-95% of the diarylthallium trifluoroacetate. Methyl- and phenyl thallium diacetates react similarly. Although the role of the trimethylphosphite is uncertain, the synthesis is useful for diarylthallium(III)s from the accessible arylthallium(III) bis(trifluoroacetates). 

Aryl fluorides. These halides are available from arenes by conversion to an arylthallium(lll) bis(trifluoroacetate) followed by reaction with KF, and finally reaction of the arylthallium(III) difluoride with BF3 in ether or cyclohexane. Yields are comparable to those obtained by the Schiemann reaction. ... 

Arylthallium bis(trifluoroacetate)s are converted by successive treatment with KF and BF3 into aryl fluorides.Thallium(iii) nitrate (TTN) readily oxidizes dialkyl sulphides and selenides to the corresponding sulphoxides or selenoxides, and 2-(alkylthio)-l-arylethanones (37) into compounds (38) in methanolic solution.In a modification of the TTN oxidative conversion of aryl alkyl ketones into arylacetic acids, enol ethers derived from the ketones are used instead of the ketones themselves. This reduces the formation of side products. Cyclic aralkyl ketones (39) may be ring-expanded and alkylated to give compounds (40) via treatment of their Wittig-derived alkenes with TTN/ an extrapolation of the basic reaction discovered previously. 

The thallium is initially introduced into the position that is most reactive toward electrophiles, but the reaction is reversible, so that heating gives a mixture having a composition governed by the relative thermodynamic stability of the various possible isomers. In some cases, then, thallation followed by isomerization can lead to a product with an orientation different from that obtained by direct electrophilic substitution." The arylthallium compounds can also be converted to phenols via a procedure that involves oxidation and hydrolysis" ... 

Aryl radicals, that is, CeHs, which have been generated thermally by the decomposition of, for example, aryl diazonium salts (ArN2 ) in the presence of copper(I) salts (Equation 6.113) and the decomposition of diacyl peroxides (Equation 6.114), or photolytically from aryl iodides (e.g., iodobenzene, CeHsl) (Equation 6.115) and arylthallium trifluoroacetates as shown in Equation 6.116, react with benzene (CeHe) to give biphenyl (CeHs-CeHs) (Scheme 6.97). 

Syntheses of dialkylthallium halides with bulky alkyl groups such as trimethyl-silylmethyl and neopentyl have been described, these compounds are dimeric. (Acyloxy)arylthallium compoimds have been prepared from organotin compounds, reactions (40), (41). ... 

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