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DOI: 10.1055/sos-SD-234-00262

Bietti, M.; Dénès, F.Science of Synthesis: Free Radicals: Fundamentals and Applications in Organic Synthesis, (20211535.

In 2015, Swamy and Allu reported a procedure for the ortho acylation of 6-(phenylamino)purines/purine nucleosides via palladium(II)-catalyzed CH activation.[‌137‌] The reaction is carried out by mixing the 6-(phenylamino)purine (1 equiv) with a twofold excess of an aliphatic aldehyde at 110 °C in a 7:2:1 mixture of 1,4-dioxane/acetic acid/dimethyl sulfoxide, in the presence of palladium(II) acetate (10 mol%) and tert-butyl hydroperoxide, the role of which is to provide an alkoxyl radical source to generate the acyl radical (Scheme 57). The latter reacts with a six-membered cyclopalladated intermediate 34 that is formed upon CH activation promoted by the purine N1 atom, and gives a palladium(IV) intermediate 35, which undergoes reductive elimination yielding the ortho-acylation product, thus regenerating the active palladium(II) species. The Kuang group reported a similar procedure for the palladium(II)-catalyzed acylation of 2-aryl-1,2,3-triazoles with aldehydes.[‌138‌]

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