2-Pyridinyl silver

In 2006, Yu et al. combined pyridinyl-directed C-H activation and C-C bond formation with alkylboronic acids (see Section 10.5.4.2).23 The success of this transformation relied on the combination of palladium acetate (10 mol%), benzoquinone (1 equiv), and silver oxide or carbonate (0.5 equiv) in a protic solvent, but an excess of boronic acid (3 equiv) was required (Scheme 10.9). Interestingly, in this reaction silver oxide played a dual role as promoter for the transmetallation step and as cooxidant with benzoquinone. 

Stille reactions have been improved by the addition of silver salts. For example, 5-iodouracil could be coupled with stannylated pyridine, forming 5-(2-pyridinyl) uracil in good yield (Scheme 10.39).67... 

As before, a silver ion and its counterion could act together in the transmetallation step, such as depicted in Scheme 10.44. Such a hypothesis seemed supported by the discovery in 2006 that 2-pyridinyl, but not 3-pyridinyl, allylsilanes reacted under similar conditions and transferred the pyridine moiety to various aryl iodides (Scheme 10.45).78 In this coupling, the nitrogen atom of the pyridinyl moiety probably played a role similar to that of the hydroxyl group in the silanol-based Hiyama couplings. 

Heptafluoro-2,2-dimethyl-3,5-octanedionato-0,0 )silver, H-00005 2-Hydroxybenzoic acid [2-(2-pyridinyl)ethylidene]hydrazide, H-00121... 

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