Thallium(I) Carbonate1


[6533-73-9]  · CO3Tl2  · Thallium(I) Carbonate  · (MW 468.77)

(base; promoter of coupling reactions)

Physical Data: mp 272 °C; d 7.110 g cm-3.

Solubility: sol 24 parts water; 3.7 parts boiling water; sol typical organic solvents; insol alcohol.

Form Supplied in: white solid; commercially available. Drying: decomposes on heating.

Handling, Storage, and Precautions: all thallium compounds are extremely toxic to inhalation, skin contact, and ingestion. Toxicity is cumulative. Extreme caution should be used when handling these materials. Use in a fume hood.

General Discussion.

Thallium carbonate exhibits a variety of interesting applications. The most important of these is the use of thallium carbonate in the Suzuki palladium-catalyzed cross-coupling reaction of alkylboronic esters.2 As shown in eq 1, the coupling reaction occurs in high yield to give the hydrocarbon product. Thallium(I) Hydroxide can also be used as the base for this valuable transformation, but thallium carbonate offers the advantage of nonaqueous conditions.

Thallium carbonate has also been used to generate thallium carboxylates, which are then transformed to the alkyl bromide in a thallium version of the Hunsdieker reaction (eq 2).3 These researchers found that the carbonate was a better reagent than thallium ethoxide for preparing the thallium carboxylates, due to its increased stability.

Both thallium carbonate and Thallium(III) Nitrate have been examined as additives for promotion of a palladium-catalyzed tandem cyclization-anion capture protocol (eq 3).4 The presence of this particular additive affects the ratio of the cyclized product (2) to the direct capture product (1).

The use of thallium carbonate to generate macrocyclic lactones has been investigated,5 as shown in eq 4. While the thallium salt did effectively promote the ring closure, it was found that Cesium Carbonate was a superior reagent in this regard.

Thallium carbonate has been utilized in transesterifications with the sensitive epoxy alcohol 2,3-epoxypropanol (eq 5).6 It was found that thallium salts could mediate the transesterification without accompanying decomposition of the epoxypropanol. A very wide range of thallium salts (both TlI and TlIII) was examined. There was no significant difference in the outcome of the reaction among the various salts.

Thallium carbonate is also used in the preparation of thallium zeolite, an insoluble promoter for O-glycosylation reactions.7 The zeolite is prepared by stirring 4&AAring; molecular sieves with thallium carbonate in water, followed by washing with water, then acetone, and drying at 190 °C. The glycosylation reaction, using a fourfold excess of the zeolite, proceeds smoothly in 30-90% yields, with the thallium zeolite behaving similarly to Ag, Co, and Cd zeolites.

1. (a) McKillop, A. PAC 1975, 43, 463. (b) McKillop, A.; Taylor, E. C. In Comprehensive Organometallic Chemistry; Wilkinson, G.; Ed.; Pergamon: Oxford, 1982; Vol. 7, p 465.
2. Sato, M.; Miyaura, N.; Suzuki, A. CL 1989, 1405.
3. Cambie, R. C.; Hayward, R. C.; Jurlina, J. L.; Rutledge, P. S.; Woodgate, P. D. JCS(P1) 1981, 2608.
4. Grigg, R.; Loganathan, V.; Sukirthalingam, S.; Sridharan, V. TL 1990, 31, 6573.
5. Kruizinga, W. H.; Kellogg, R. M. JACS 1981, 103, 5183.
6. Zondler, H.; Trachsler, D.; Lohse, F. HCA 1977, 60, 1845.
7. Whitfield, D. M.; Shah, R. N.; Carver, J. P.; Krepinsky, J. J. SC 1985, 15, 737.

Mukund P. Sibi

North Dakota State University, Fargo, ND, USA

Nancy E. Carpenter

University of Minnesota, Morris, MN, USA

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