(1.2 equiv) as base under irradiation of blue LED (40 W, 456 nm) in MeCN furnished the best result for the defluorinative alkylation reaction, and the desired difluoroalkene 3a was attained as single isomer (>99:1) in 97% GC yield and 81% isolated yield (Entry 1). Several other photocatalysts were tested, but they gave remarkably lower yields (Entries 2-4). Notably, organic photocatalysts such as Me-Acr-Mes and 4CzIPN displayed excellent chemo-selectivity for the formation of 3a, whereas the iridium complex fac-[Ir(ppy)3] produced a mixture of 3a and 4a with reduced chemo-selectivity. The choice of reductant was found to significantly impact the chemo-selectivity between 3a and 4a (Entries 5-7). While using HE2 as the reductant afforded 3a in 74% yield with excellent chemo-selectivity (>99:1), other reductants led to poorer results. Base selection also influenced chemo-selectivity. While Cs2CO3 and K2CO3 furnished excellent chemo-selectivity but diminished yield (Entries 8 and 9), the use of sodium counterparts resulted in extremely poor results (Entries 10 and 11). Among various solvents tested, DMF and THF were competent solvents, delivering product 3a as a single isomer despite much lower yields (Entries 12 and 13). To our surprise, when toluene was used as the solvent, a turnover of the chemo-selectivity was observed to forge the trifluoroalkane 4a as the major product (3a:4a = 1:10) (Entry 14). Control experiments demonstrated that Eosin Y, HE1 and K3PO4 are all critical for the selective defluorinative alkylation pathway, and their removal led to significantly reduced yields and chemo-selectivity (Entries 15-17). Notably, in the absence of both Eosin Y and K3PO4, the hydroalkylation pathway in MeCN predominated to give 4a as the major product in 76% yield with a chemo-selectivity of 1:5(Entry 18). As previously mentioned, solvent choice exerts a tremendous influence on chemo-selectivity, and using toluene improved the chemo-selectivity to 1:12 (Entry 19). Further investigation into solvent sources revealed that the chemo-selectivity could be further enhanced by THF (Entry 20). Evaluation of Hantzsch ester derivatives demonstrated that HE2 was the most effective reductant, improving both the yield and the chemo-selectivity. In contrast, the use of other Hantzsch ester derivatives HE3 and HE4 gave rise to comparable results to that of HE1 (Entries 21-23). Therefore, the optimal reaction conditions involve HE2 (1.5 equiv) under the blue LED irradiation (40 W, 456 nm) in THF, arriving at 4a in 76% isolated yield and a chemo-selectivity of 24:1. In this transformation, an EDA complex between pyrrolidin-2-ylmethanol-derived N-alkoxyphthalimide and Hantzsch ester HE2 is proposed to form, and HE2 was obligatory for the occurrence of this reaction (Entry 24). Control experiments implied that light irradiation was necessary for both the defluorinative alkylation and the hydroalkylation pathways (Entries 25 and 26).With the optimal reaction conditions established, we next explored the substrate scope for the synthesis of gem-difluoroalkens. As shown in Scheme 2, the β-scission/gemdifluoroallylation reaction was successful with a wide range of N-alkoxyphthalimides derived from primary, secondary, and tertiary aliphatic alcohols. N-alkoxyphthalimides derived from various Boc-protected amino alcohols, such as valinol, phenylalaninol and cyclohexyl-substituted amino alcohol proved to be excellent reaction partners, affording the targeted products 3b-d in high yields (75-93%) and consistently excellent chemo-selectivity (50:1 ->99:1). Similarly, O-bearing cycloalkyl rings were effectively converted to the desired difluoroalkenes 3e-3g though with somewhat reduced chemo-selectivity (9:1 -30:1). In these cases, stabilized α-amino or α-oxo radicals were generated from N-alkoxyphthalimides. To our delight, primary, secondary, and tertiary alkyl radicals without an adjacent heteroatom could also be accommodated into this transformation (3h-k). It should be mentioned that for the generation of unstabilized secondary and primary alkyl radicals lacking an adjacent heteroatom, additional methyl or phenyl substituents need to be present at the ortho-position of the hydroxyl group to drive the β-scission event (3j-k; 1i vs 1i'). The substrate scope of this reaction was then extended to cyclic tertiary alcohol (3l) and O-phthalimido cyclic hemiacetal (3m and 3n) derived N-alkoxyphthalimides, leading to the formation of ring-opening ketone or formate-tethered gem-difluoroalkenes in moderate to excellent yields and chemo- selectivity. Notably, the alkyl radical could also be produced via a 1,5-hydrogen atom transfer (HAT) event, and the corresponding product 3o was attained with 83% yield and 37:1 chemo-selectivity. The generality of the α-trifluoromethyl styrene partner was also investigated. As depicted in Scheme 2B, the β-scission/gem-difluoroallylation event tolerated a wide range of functional groups on the phenyl ring of the α-trifluoromethyl styrene partners, including aryl (3a), alkyl (3r, 3s), ether (3t-a'), chloro (3b', 3c'), cyano (3d'), and amide (3m'), thereby delivering the targeted products in good yields (46-93%) and chemo-selectivity (6:1 ->99:1). The steric characteristics did not Scheme 3. Substrate scope for the synthesis of trifluoroalkanes 4.