Selective Azidooxygenation of Alkenes Enabled by Photo-induced Radical Transfer Using Aryl-λ³-azidoiodane Species

Abstract

The photolytic radical-induced vicinal azidooxygenation of synthetically important and diverse functionalized substrates including unactivated alkenes is reported. The photoredox-catalyst/additive-free protocol enables intermolecular oxyazidation by simultaneously incorporating two new functionalities; C–O and C–N across the CC double bond in a selective manner. Mechanistic investigations reveal the intermediacy of the azidyl radical facilitated via the photolysis of λ3-azidoiodane species and cascade proceeding to generate an active carbon-centered radical. The late-stage transformations of azido- and oxy-moieties were amply highlighted by assembling high-value drug analogs and bioactive skeletons.

Hypervalent Iodine‐Mediated Azidation Reactions

“…Very recently a similar hetero‐atoms insertion into the aliphatic skeleton was reported [12] . So, a selective azidooxygenation of olefins 19 enabled by photo‐induced radical transfer using generated in situ azidoiodinane 18 and TEMPO gives azides 20 (Scheme 3).…”

“…[11] Very recently a similar hetero-atoms insertion into the aliphatic skeleton was reported. [12] So, a selective azidooxygenation of olefins 19 enabled by photo-induced radical transfer using generated in situ azidoiodinane 18 and TEMPO gives azides 20 (Scheme 3). The developed method is amenable to a diverse array of substrates including vinylarenes, allylic or unactivated alkenes, heterocycles, and natural products bearing synthetically useful functionalities.…”

Taming Bromine Azide for Use in Organic Solvents─Radical Bromoazidations and Alcohol Oxidations

“…Another way to achieve azidooxygenation of alkenes is by employing the explosive, in situ formed PhI(N 3 ) 2 and the TEMPO radical. 13 In the presence of 1, we isolated 1,2-adduct 14 rather than 1,2-bromoazide 11a, irrespective whether the 1,2-addition was carried out under thermal or photochemical conditions. Obviously, the radical, formed upon addition of the azide radical to the alkene, was rapidly captured by TEMPO and not by a bromine radical.…”

“…Studer et al had previously described the azidooxygenation of alkenes using Zdhankin’s reagent and in situ formed TEMPO (from TEMPONa), but in the absence of a bromide source such as phosphonium salt 1 . Another way to achieve azidooxygenation of alkenes is by employing the explosive, in situ formed PhI­(N 3 ) 2 and the TEMPO radical …”

Radical Oxyazidation of Alkenes in Pure Water

“…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 ).…”