Photoswitchable Regiodivergent Azidation of Olefins with Sulfonium Iodate(I) Reagent

Abstract

Photoswitchable strategy for selective azidation of structurally diverse olefins under transition-metal-free conditions is reported. The unprecedented reactivity of trimethylsulfonium [bis­(azido)­iodate­(I)] species under visible light allows radical azidooxygenation of the CC π bond with distinctive selectivity. In the absence of visible light, the reaction proceeds through an ionic intermediate which led to complementary regioselectivity to provide α-alkyl azides. Mechanistic studies reveal that light-controlled regiodivergent azidation involving radical or an ionic pathway can be accomplished with exclusive regioselectivity.

Radical Oxyazidation of Alkenes in Pure Water

“…Substrates 25s , 26s and 27s were prepared according to the literature, 15 18 and the remainder were purchased from commercial sources. Compounds 1 – 5 , 7 , 8 , 11 , 13 – 15 , 17 – 19 , 22 – 24 and 28 – 30 are known, 9a f g 15 16 19 and their characterization data are in accordance with the literature. The 1 H and 13 C NMR data for these compounds are provided here for the sake of completeness.…”

“…13 Pioneered by Studer, 9a radical oxyazidation of alkenes has been achieved through (photo)redox processes, iron catalysis, and electrochemical protocols, respectively. 9` c d e f g h i j k Nevertheless, this important difunctionalization reaction was limited to the use of organic solvents, which is a challenge as well as an important issue confronted in the majority of radical difunctionalizations of alkenes. Herein, we disclose a copper(II)-catalyzed, radical difunctionalization of alkenes with only pure water as the solvent (Scheme 1b ).…”

Photochemical Transformations with Iodine Azide after Release from an Ion‐Exchange Resin

“…The resulting metastable charge‐transfer complex with azide 16 (TEMPO + /N 3 − ) decomposes to TEMPO and the azide radical ( 6 ) . Recently, Kashya and co‐workers published the first photocatalyzed azidooxygenation that relied on trimethylsulfonium [bis(azido)iodate(I)] species, which are generated in situ from trimethylsilyl azide and sulfonium bis(acetoxy)iodate(I) …”

Chemical versatility of azide radical: journey from a transient species to synthetic accessibility in organic transformations

“…Notably, Kashyap et al extended their previous photocatalytic diazidation method and envisioned that the benzylic radicals, generated by the addition of N 3 , could promptly combine with the persistent TEMPO radicals to accomplish the azidooxygenation reaction with a similar approach. 110 This method embarks the photoswitchable approach for the regioselective azidation of alkenes under metal-free conditions, where the orthogonal reactivity of the Me 3 SI(N 3 ) 2 species, generated in situ from [Me 3 SI(OAc) 2 ] and TNSN 3 , toward p-bond is noteworthy to mention. Under the visible-light conditions, they achieved the azidooxygenation products for a diverse range of olefins with moderate to good yields.…”