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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, (20211542.

In 1994, the Kita group reported the direct azidation of 4-alkylanisoles using [bis(trifluoroacetoxy)iodo]benzene and azidotrimethylsilane.[‌175‌] Later, in 2001, Bols and Viuf reported the azidation of activated CH bonds (typically benzyl ethers), using iodine azide (IN3) in refluxing acetonitrile.[‌176‌] Owing to the weak IN3 bond, homolytic cleavage leading to the azidyl radical N3 is easily achieved upon heating. The azidyl radical can then play the role of a HAT reagent [BDE(HN3) = 93.3 kcal · mol−1][‌177‌] for activated CH bonds (Scheme 66). A disadvantage of this reaction is the requirement for an excess of iodine azide, a hazardous and explosive reagent, particularly as a solid. The Bols group later reported safer conditions with the use of 1.3–4 equivalents of the azidotrimethylsilane/(diacetoxyiodo)benzene combination to produce in situ the corresponding azidoiodinane reagent.[‌178‌] The procedure gives similar yields to those obtained with iodine azide but can be carried out under milder (and thus safer) conditions (25 °C). The addition of the azidyl radical to alkenes is sometimes observed as a side reaction. With the use of more reactive reagents or modified conditions, the range of CH bonds that can participate in the azidation reaction can be extended to include aliphatic CH bonds (see Section

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