Thallium , rate enhancement

Silver salts are also common activators in numerous Suzuki coupling reactions. The earliest example could probably be found in the Kishi s palytoxin synthesis. Silver oxide as well as thallium hydroxide provided dramatic rate enhancements in the couplings of vinylboronic acids (Scheme 10.41).69 Both thallium and silver ions are most probably abstracting halide in palladium intermediates, but silver is clearly the most efficient. Moreover, with the right counterion, the silver salt also acts as a mild base and activator. 

Thallium trinitrate has been shown to be an efficient reagent for the dehydrogenation of chroma-nones and flavanones (Table 10, entry 5). the reaction being carried out in methanol at room temperature. The addition of perchloric acid to chromanone oxidations enhances the yields and reaction rates by promotion of enolization, but qiparently was without effect on flavanones. The ease with which chimanones and similar compound may be dehydrogenated has also permitted unusual procedures such as trimethylsilyl chloride/acetic anhydride and photolysis to be used (Table 10, entries 6 and... 

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