At the outset of our studies, we elected to explore the alkene chloroarylation reaction using two electronically distinct alkenes, thereby enabling us to probe the hypothesis that catalysts could be tailored to different substrates. Our initial reactions assessed styrene 2a (4.0 equiv.) in combination with diphenyl iodonium triflate 1a (1.0 equiv.) -as the aryl radical precursor -and KCl (2.0 equiv.) in the presence of photocatalyst [Ru(II)(bpy)3](PF6)2 A-i, and the chlorine atom-transfer precatalyst [(bpmen)Fe(II)Cl2] (as a precursor to in acetonitrile under irradiation with a 40 W blue LED lamp. This initial reaction delivered the desired β-arylethyl chloride 3a in 58% yield, determined by 1 H NMR spectrometry (Table , entry 1, see Figure for the structures and physical properties of the photocatalysts and group transfer catalysts). While the use of fac-[Ir(III)(ppy)3] (A-ii) as an alternative photocatalyst did not significantly improve the yield of 3a (entry 2), we were pleased to observe that 3a was obtained in almost quantitative assay yield in the presence of Cu-based photocatalyst A-iii ([Cu(I)(dpp)2](PF6) (entry 3). Two Cu(II)-group transfer catalysts displaying pyridyl-imine ligands were also evaluated in the presence of the Cu-photocatalyst A- iii(entry 4 and 5), because similar salts have proved to be effective in our previous alkene azido-arylation studies but no improvement was observed . When changing the alkene from styrene to the electrondeficient methyl acrylate (2b), we found a reaction using a combination of the [Cu(I)(dpp)2](PF6) photocatalyst (A-iii) and the Fe group-transfer catalyst (B-i) led to a low yield of the desired product. When switching to the group transfer catalyst, a Cu(II)-salt ligated with N-t-butyl-2-quinolinecarboxaldimine B-ii, which had proven to be an excellent azide-transfer catalyst across reactions with a range of electron-deficient alkenes in our previous studies , only a modest improvement to the yield of 3b (39%, entry 7) was observed. However, tailoring the ligand backbone of the group transfer catalyst to a Cu(II)-complex bearing N-t-butyl-2-pyridinecarboxaldimine (B- The reaction outcome of these catalyst systems when operating with different alkenes can be rationalized by considering the nature of the electron transfer in each system. The highly efficient chlorine transfer from the Fe-bpmen complex B-i is rationalized by the electron flow in the transition state from the homobenzylic radical towards the iron center, which can lead to the generation of partial positive charge on the carbon and stabilized by neighboring electron-donating functionality . On the other hand, the higher efficiency of the Cu-based B-iii complex as a chlorine atom transfer-catalyst the reaction with an electron-deficient alkene may be explained by a gradual electron transfer from the copper center to the homobenzylic radical during the transition state of C-Cl bond forming step. This results in the build-up of partial negative charge on the carbon atom and can be stabilized by the proximal electron-withdrawing group 18 .A series of control experiments were performed using styrene 2a (see section II.1.14 and II.2.3 in the Supporting Information). These experiments revealed that desired product 3a was not observed in the absence of visible-light. Removal of Cu(I)-photocatalyst (A-iii) resulted in a 55% yield of 3a, suggesting that Fe(II) catalyst is reasonably competent at generating the aryl radical as well as functioning as a group transfer agent. A reaction in the absence of the Fe(II)group transfer catalyst (B-i) resulted in a 6% yield of 3a, the low yield of which can be most likely explained by a partial decomposition of the oxidized Cu-photocatalyst, to form a mono-dpp-ligated Cu(II)species, which is capable of facilitating the Cl-atom transfer. Other combination of catalysts (see section II.1.1, II.2.1 and II.2.2 in the Supporting Information) and solvents (see section II.1.2 in the Supporting Information) were also evaluated but returned inferior results to the Cu/Fe and Cu/Cu dual catalyst systems. In summary, distinct optimal conditions were identified for styrenes and electron-deficient alkenes. Accordingly, exposure of an anhydrous acetonitrile solution of diphenyliodonium triflate (1.0 equiv.), alkenes (4.0 equiv.) and potassium chloride (2.0 equiv.) to compact fluorescent lamp (CFL) irradiation in the presence of [Cu(I)(dpp)2](PF6) (2.0mol%, photocatalyst A-iii) and the appropriate chlorine atom transfer pre-catalyst: [(bpmen)Fe(II)Cl2] (10mol% pre-catalyst B-i) is efficient to facilitate the chlorination process when styrenes are used; 2mol% of the Cu(I)-precatalyst, C, generated in situ from [Cu(I)(MeCN)4](PF6) and BPA, was optimal for reaction with electron-deficient alkenes.