Thallium(I) Hydroxide1

TlOH

[4310-83-4]  · HOTl  · Thallium(I) Hydroxide  · (MW 221.39) (.H2O)

[12026-06-1]

(base; additive for cross-coupling reactions)

Physical Data: mp 139 °C (dec).

Solubility: sol water, ethanol.

Form Supplied in: yellow needles; 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 hydroxide has been found to be an especially useful base for the enhancement of the Suzuki cross-coupling of alkyl boronic acids and esters with vinyl and aryl halides.2 This thallium hydroxide-mediated transmetalation has been used for the preparation of a key diene in the synthesis of palytoxin (eq 1).3 The use of TlOH instead of Potassium Hydroxide resulted in a dramatic 1000-fold rate enhancement.

This method was also successfully used as a diene preparation in an approach to the bottom half of chlorothricolide (eq 2).4 The yield of this transformation was considerably improved by the use of thallium hydroxide (cf. 55% for Sodium Hydroxide). It is interesting to note that the boronic acid ester was used in this transformation. Like Suzuki,2 these researchers found the ester gave better results. However, in subsequent work4b it was determined that the boronic acid gave optimal results, presumably due to ease in purification of the acid derivatives.

Thallium hydroxide has been used in the preparation of thallium(I) salts of b-keto esters.5 These thallium salts are subsequently condensed with various electrophiles to obtain useful adducts (eq 3).

Thallium hydroxide has also been studied in the condensation of Formaldehyde with a-hydroxy ketones, and found to be better than calcium hydroxide in terms of solubility and catalytic action.6


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. (c) Taylor, E. C.; McKillop, A. ACR 1970, 3, 338.
2. Sato, M.; Miyaura, N.; Suzuki, A. CL 1989, 1405.
3. Uenishi, J.; Beau, J-M.; Armstrong, R. W.; Kishi, Y. JACS 1987, 109, 4756.
4. (a) Roush, W. R.; Riva, R. JOC 1988, 53, 710. (b) Roush, W. R.; Moriarty, K. J.; Brown, B. B. TL 1990, 31, 6509.
5. (a) Hase, T. A.; Suokas, E.; McCoy, K. ACS 1978, 32, 701. (b) Suzuki, E.; Inoue, S. S 1975, 259.
6. Guillot, G.; Sadet, J.; Rumpf, P. BSF(2) 1972, 6, 2393.

Mukund P. Sibi

North Dakota State University, Fargo, ND, USA

Nancy E. Carpenter

University of Minnesota, Morris, MN, USA



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