Iron-catalyzed radical Markovnikov hydrohalogenation and hydroazidation of alkenes

We herein report radical hydroazidation and hydrohalogenation of mono-, di- and trisubstituted alkenes through iron catalysis. The alkene moiety that often occurs as a functionality in natural products is readily transformed into useful building blocks through this approach. Commercially available tosylates and α-halogenated esters are used as radical trapping reagents in combination with silanes as reductants. The reported radical Markovnikov hydroazidation, hydrobromination, hydrochlorination, and hydroiodination occur under mild conditions. These hydrofunctionalizations are valuable and practical alternatives to ionic hydrohalogenations with the corresponding mineral acids that have to be run under harsher acidic conditions, which diminishes the functional group tolerance. Good to excellent diastereoselectivities can be obtained for the hydrofunctionalization of cyclic alkenes. Alkenes are attractive building blocks for synthetic organic chemists as they are widely available and can be functionalized in ways that enable manifold further transformations. Here, the authors present a suite of hydrofunctionalizations of alkenes that lead to regioselective delivery of azides and halogens, under mild conditions, with iron catalysis.