Anti‐Markovnikov Hydroazidation of Alkenes by Visible‐Light Photoredox Catalysis

Abstract

The anti‐Markovnikov hydroazidation of alkenes has been accomplished under visible‐light irradiation by using [Ir(dF(CF3)ppy)2(dtbbpy)]PF6 as the photocatalyst and trimethylsilyl azide as the azidating agent. The reactions were greatly facilitated by water, the beneficial effect of which can be attributed to its participation in the reaction as the hydrogen donor, as indicated by deuterium isotope experiments. The reactions proceed under solvent free conditions in the presence of water. 4‐Dimethylaminopyridine also exhibited a beneficial effect on the reactions. The present method enabled hydroazidation of several types of unactivated alkenes with good yields and high regioselectivity.

Catalytic Azido‐Hydrazination of Alkenes Enabled by Visible Light: Mechanistic Studies and Synthetic Applications

“…Since the azo‐ene reaction is a potential competing pathway, we deliberately selected but‐3‐en‐1‐yl benzoate ( 1 a ) that possesses allylic C−H bonds as a model substrate for the catalyst discovery and condition optimization. Current methods that convert TMSN 3 to azide radicals under visible light require sophisticated photocatalysts such as Ir‐complexes, acridinium salts, Rose Bengal and sulfonium iodate . Following our recent discoveries, simple ketone photo‐sensitizers were first attempted to generate azide radical due to their availability.…”

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

“…Mostly, anti-Markovnikov olefin hydroazidations are accessed by indirect or multi-step process, but only a few reports are known for direct anti-Markovnikov hydroazidations in the literature. [115][116][117][118][119] Indeed, radical-mediated addition reaction is one of the most convenient strategies for anti-Markovnikov selectivity. N 3 can indeed add to the less-substituted side of an unactivated alkene, thus forming a new C-N 3 bond in an anti-Markovnikov fashion.…”

Transition Metal Catalyzed Azidation Reactions

“…Depending on the ligand structure, the active cobalt complex can be synthesized or generated in situ. Recently, Wang and Yu proposed an innovative anti-Markovnikov hydroazidation of unactivated alkenes exploiting an Ir(III) complex for a visible light photoredox protocol (Scheme 80) [147]. The employment of TMS-N 3 as azide source, combined with the use of dimethylamino pyridine (DMAP) and water, permitted to functionalize a wide range of terminal alkenes showing a good tolerance for nitrogen-and oxygenated functional groups.…”