Thallium I hydroxide

Thallium (I) hydroxide (Tl + OH " —> TlOH) is used in optical glass. 

The reaction of Ba(OH)2 and T12S04 in oxygen-free aqueous solution yields aqueous thallium(I) hydroxide, but the solid is best obtained from the metal and aqueous ethanol in the presence of oxygen. The yellow crystalline solid yields an alkaline solution. The mixed oxides MTIO (M = K, Rb) have been prepared by heating M20 and T120, but these are apparently not thaUate(I) spedes.294... 

To a solution of 5.0 g. (0.02 mol) thallium (I) formate in 3.0 ml. of water, 1.0 g. of solid sodium hydroxide is added. Yellow thallium (I) hydroxide crystals precipitate in nearly 100% yield if the solution is stirred until all the sodium hydroxide dissolves. The solution is filtered through a sin-tered-glass filter while it is still warm. The thallium (I) hydroxide is washed with benzene and dried for 5 minutes by air drawn through the filter. Such air is made carbon dioxide-free by passing it through a drying tube filled with Ascarite. 

Ethanol (4 ml.) is added to 4.4 g. (0.02 mol) of thallium (I) hydroxide in a 50-ml. beaker, and the mixture is stirred until nearly all the yellow solid disappears. To dissolve the thallium (I) ethoxide selectively, 20 ml. of benzene is added. After decanting, the extraction is repeated to increase the yield of ethoxide. The clear, filtered solution of ethoxide is added to a solution of 3.24 g. (0.02 mol) benzoylacetone (l-phenyl-l,3-butanedione) in 20 ml. of benzene. The impure thallium (I) benzoylacetonate is collected by evaporating the solvent under reduced pressure. Purification is accomplished by dissolving the impure product in 25 ml. of benzene and reprecipitating with an equal volume of petroleum ether (b.p. 90 to 110°). (The checkers report that it was necessary to scratch the flask to induce crystallization.)... 

Compared with the versatile utility of Tl(III) salts in organic synthesis, the use of T1(I) salts for this purpose is still limited. The most useful reagents are thal-lium(I) ethoxide and thallium(I) hydroxide. The former reacts with /1-diketones, phenols, carboxylic acids, and pyridones, etc., to give the corresponding T1(I) salts which can subsequently be used for a variety of organic transformations, as shown in Schemes 9.78 [77], 9.79 [78], 9.80 [78], 9.81 [79] and 9.82 [80]. 

Either JV- (65) or 5-amino (66) products are formed if the 2-thioxothiazin-4-ones (67) are reacted with 0-(diphenylphosphoryl)hydroxylamine in contact with thallium(I) hydroxide, or sodium hydride, respectively (Scheme 7) <87AP(320)67>. 

HCIO4 HNO3 H2SO4 HCl HBr HI Perchloric acid Nitric acid Sulfuric acid Hydrochloric acid Hydrobromic acid Hydroiodic acid LiOH NaOH KOH RbOH CsOH TlOH Ca(OH)2 SK0H)2 Ba(OH>2 Lithium hydroxide Sodium hydroxide Potassium hydroxide Rubidium hydroxide Cesium hydroxide Thallium(I) hydroxide Calcium hydroxide Strontium hydroxide Barium hydroxide... 

The ethoxide obtained fromlOg, ofTl (see thallium(I) hydroxide, p. 877, for preparation] is dissolved in 250 ml. of absolute alcohol and passed through a fluted filter into the flask of a distillation apparatus. Air is displaced with pure Ng, followed by dry HgS, resulting in a finely divided TlgS precipitate. Air is prevented from entering the apparatus by having the condenser tube reach almost to the bottom of the receiver, which contains some alcohol. 

Solutions in benzene can be prepared by conversion of thallium(I) acetate in water to thallium(I) hydroxide by reaction with NaOH. This material is dried, suspended in benzene and ethanol (1 equiv.), and stirred for 24 hours under Na. Thallium(I) ethoxide is obtained in this way in benzene solution in about 95% yield. ... 

Teuber reaction 8, 206 16, 222 Thallium(III) acetate 19, 189 —, oxidations with — 18,185 Thallium(I) hydroxide 16, 334 Theophyllines... 

Scheme 20.15). One equivalent of hydroxide or alkoxide is necessary to replace the halogen on the palladium complex I and the second equivalent is essential to form the borate II, so that the allq l group becomes more nucleophilic. According to Kishi and coworkers,the advantage of using thallium(i) hydroxide over sodium hydroxide is that the first can form insoluble thallium halide (TlX) which contributes to enhance this step and to accelerate the coupling. 

Lera and coworkers successfully employed this thallium(i) hydroxide-aecelerated Suzuki reaction in the stereocontrolled polyene syntheses of retinol (vitamin A) and derivatives and polyenic alarm pheromones of cephalaspidean molluscs navenone A and haminol Despite some initial examples where thallium(i) ethoxide failed as an alternative for thallium(i) hydroxide there are an appreciable number of cases where thallium(i) ethoxide furnished great results. The first successful use of thallium(i) ethoxide was reported by Chamberlin and coworkers in the total synthesis of microcystin LA, a serine-threonine phosphatase inhibitor (Scheme 20.17). A few years after the synthesis of mieroeystin L, Roush and coworkers extended the use of thallium(i) ethoxide in Suzuki couplings for a range of boronic acids and halides. Simultaneously, Danishefslq and Chemler ... 

Since an aqueous solution of thallium(i) hydroxide is air and light sensitive, and there are limited commercial sources of this reagent, its replacement by thallium(i) ethoxide seems to be an excellent alternative to accelerate palladium(0)-catalysed crosscouplings. Although toxic, thallium(i) ethoxide is an easily handled liquid, more stable and readily available from several commercial sources. ... 

The remaining oxides and hydroxides, as expected from our earlier discussion in Section 11.3, become progressively more basic down the group. Consistent with the inert-pair effect, the more stable oxide and hydroxide of thallium are TI2O and TlOH, not TI2O3 and Tl(OH)3. lhallium(I) oxide is a mild basic anhydride, whereas thallium(I) hydroxide is a moderately strong base. 

Peroxide. Thallium(l-l-) is oxidized to Tl by Na202. Thallium(I) hydroxide is readily oxidized by H2O2. 

Carbon oxide species. Thallium(I) hydroxide is about as basic as NaOH. It rapidly absorbs CO2 from the air. A dilute solution of TT gives no precipitate with C03 , which, however, in air, precipitates brown Tl203 aq, insoluble in excess. 

Roush has demonstrated that thallium(I) ethoxide promotes Suzuki-coupling for a range of functionalized alkenyl boronic acids and functionalized aryl or alkenyl halides in good to excellent yields [101]. This reagent offers distinct advantage over thallium(I) hydroxide in terms of its commercial availability, stability and ease of use (Scheme 3.66). 

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