Thallium(III) in Organic Synthesis

Abstract

This review article discusses the literature regarding thallium(III) compounds in synthetic organic chemistry published in the last decade, including several applications in the total synthesis of natural products. The reactions that received the most attention in this period were: i) the oxidative rearrangement of chalcones; ii) the ring contraction of cyclic alkenes; iii) the oxidation of homoallylic alcohols; iv) aromatic thallations; and v) oxidative couplings, including with phenols.

Iodine(III)-Mediated Ring-Contraction Reactions Using Halogenated and Non-halogenated Solvents

“…1 The treatment of ketones and alkenes with particular oxidants, such as thallium(III) or iodine(III), can lead to an oxidative rearrangement. [9][10][11] A ring-contraction reaction occurs when these salts are used with cyclic ketones and alkenes. 9 Ring contractions mediated by these oxidants are easier, more efficient, and more versatile than anionic, cationic, or free radical rearrangements.…”

“…1,14,15 These solvent systems not only change the reactivity patterns of the ring-contraction reaction but also alter the functionality of the corresponding indane from a common precursor. 10 Despite being very effective in ring-contraction reactions, the use of thallium reagent is undesirable because of its severe toxicity. 16,17 As an alternative to thallium salts, the environmentally benign hypervalent iodine reagent hydroxy(tosyloxy)iodobenzene (HTIB) has been utilized.…”