Expanding the Scope of Photocatalysis: Atom Transfer Radical Addition of Bromoacetonitrile to Aliphatic Olefins Errika Voutyritsa, Ierasia Triandafillidi, and Christoforos G. Kokotos* [a] Introduction Radical generation from alkyl halides by homolytic cleavage of the C ÀX bond leads to the incorporation of alkyl moieties in carbon chains, providing useful intermediates in organic syn- thesis. [1] Photocatalysis allows the generation of these radicals under mild conditions, following various mechanisms, includ- ing hydrogen abstraction from alkanes or halide abstraction from alkyl halides. These alkyl radicals are versatile as reactive intermediates, in particular for C ÀC bond formation events making this method appealing. Atom transfer radical addition (ATRA) or atom transfer radical cyclization (ATRC) of haloal- kanes and halocarbonyls to unsaturated compounds, forming C ÀC and C ÀX bonds, is reported with a range of metal cata- lysts, such as ruthenium, [2] iron, [3] nickel, [4] palladium, [5] iridium [6] and copper. [7] Photoredox catalysis has provided a revolution in the field, since MacMillan, [8] Yoon, [9] and Stephenson [10] have proved the ability of photoredox catalysts to introduce novel organic transformations. [11] Around the same time, Bach, [12] Ni- cewicz, [13] and Melchiorre [14] through their seminal work have developed photochemical reactions as useful tools in organic chemistry. Bromonitriles are potentially useful scaffolds for the synthesis of biologically active compounds and have demon- strated important synthetic utilities. [15, 16] The last few years, photochemical ATRA of bromoacetonitrile to olefins starts to play a dominant role among the methods reported for their synthesis. Although there are various examples of the addition of haloalkanes to olefins (Scheme 1, top), knowledge on the addition of bromoacetonitrile to olefins is rather limited (Scheme 1A–C). More specifically, in 2001, Oshima and co- workers treated bromo compounds and olefins with triethyl- borane in water to provide the corresponding products in good yields. Only one example, utilizing bromoacetonitrile, was demonstrated and the reaction employed stoichiometric amount of the promoter (Scheme 1 A). [17] In 2014, the group of Melchiorre developed a photoorganocatalytic method for ATRA of haloalkanes onto olefins (Scheme 1B). In this case, only one example using bromoacetonitrile was reported. [18a] A very recent photoorganocatalytic example, demonstrating a single example with bromoacetonitrile was also reported by Cozzi and co-workers. [18b] Also, two methods were developed for the addition of bromoacetonitrile to styrene derivatives under photoredox catalysis (Scheme 1 C). [19, 20] In both instan- ces, the olefin was only limited to styrene derivatives and the intermediate radical was trapped by the alcoholic solvent, evi- dence that this method proceeds via a carbocation intermedi- ate and that the more versatile bromide intermediates could not be isolated. We have recently turned our attention to pho- tocatalysis, both in photoorganocatalysis [21a–e] and photoredox catalysis. [21f] Herein, we describe an expansion of current knowledge into a synthetic protocol for the ATRA addition of bromoacetonitrile utilizing tris[2-phenylpyridinato- C 2 ,N]iridium(III) as the photocatalyst onto a wide substrate scope of aliphatic olefins bearing various functional groups (Scheme 1, bottom). Results and Discussion We began our investigations with the reaction between 1- decene (1a) and bromoacetonitrile with several catalysts. This reaction was chosen to overcome the current literature limita- tion with the employment of styrene derivatives. Utilizing metal complexes as the photocatalyst, high yields were ob- tained, with Ir(ppy) 3 proving to be the best photocatalyst (Table 1, entries 1–3). A range of organic photocatalysts were also tested in the reaction, providing the desirable products in lower yields (entries 7–9). After identifying Ir(ppy) 3 as the opti- mum photocatalyst, we proceeded with the optimization of the reaction conditions, studying the reaction’s performance An efficient photocatalyzed bromocyanomethylation of alkenes is reported. Among a range of organocatalysts and metal com- plexes, Ir(ppy) 3 proved to be the best photocatalyst in promot- ing the addition of BrCH 2 CN to olefins. This photocatalytic atom transfer protocol can be expanded into a wide substrate scope of aliphatic olefins bearing various functional groups, leading to the corresponding products in good to excellent yields. In addition, linchpin catalysis was developed, since the bromo group can undergo further transformation into useful functional groups, such as the synthesis of amino acids. [a] E. Voutyritsa, I. Triandafillidi, Prof. C. G. Kokotos Laboratory of Organic Chemistry Department of Chemistry National and Kapodistrian University of Athens Panepistimiopolis 15771, Athens (Greece) E-mail : ckokotos@chem.uoa.gr Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/ cctc.201800110. ChemCatChem 2018, 10, 2466 – 2470  2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2466 Full Papers DOI: 10.1002/cctc.201800110