Based on these observations a plausible mechanism is proposed for βchloroacylation of alkenes (Fig 8I). Cu(dmp)(BINAP)BF4 in its excited state can form aroyl radical I upon one-electron reduction of benzoyl chloride with the generation of Cu(II)-chloride species VIII. The radical I adds to the alkene, forming the transient radical IX, which can interact with VIII. Chlorine is then transferred via an inner-sphere radical rebound mechanism initiated by a radical capture generating transient Cu(III)-complex lV that forges the C -Cl bond in the final product through a reductive elimination. Alternatively, direct chlorine abstraction from Cu(II)-Cl species VIII by radical IX may deliver the desired product (see SI, Fig. ). For styrene derivatives bearing a strongly electron-donating para-methoxy group or an α-phenyl substituent, the reaction proceeds via a back-electron transfer mechanism where the radical intermediate IX should be oxidized to the corresponding carbocation X that subsequently combines with the chlorine anion forming product 38, 39 and 55 under regeneration of the photocatalyst. In case of aromatic alkynes, the vinyl radical intermediate XI, generated following aroyl radical I addition to alkynes, could interact with Cu(II)-chlorine intermediate VIII, leading to the formation of Cu(III)-species XII-A or XII-B (Fig. ). Formation of the Cu(III)species presumably controls the stereoselectivity of this alkyne difunctionalization process, and it is proposed that the reaction proceeds via the sterically more favored intermediate XII-A to deliver the E-β-chlorovinyl ketone selectively upon reductive elimination. Previously, Collins et al. have reported that heteroleptic copper complexes can facilitate E↔Z alkene isomerization under light irradiation via energy transfer (ET) process because of their higher triplet energy and longer excited-state lifetime. Therefore, it is also possible that following chlorine abstraction from Cu(II)center VIII by vinyl radical intermediate XI and ensuing photoisomerization in the presence of Cu(dmp)(BINAP)BF4 leads to E-selective formation of βchlorovinyl ketones (see SI, Fig. ). Moreover, to assess the efficiency of the formation of Cu(III)-species of type IV we conducted the ATRA of alkene A10 where β-chloroacylation competes with intramolecular cyclization (Fig. ). In 2022 Ngai et al. reported that reaction of alkene A10 with aroyl chloride led to the formation of heterocycle 146 via an intramolecular cyclization-aromatization pathway. Conversely, under the standard reaction conditions developed in this work, ATRA product 145 was obtained exclusively in 62% yield, pointing towards a different course of reaction pathway. In Ngai's work it was postulated the combination of [Cu(BINAP)2]PF6 and [Cu(IPr)2]PF6 as the catalytically active species where the homoleptic [Cu(BINAP)2]PF6 is responsible only for the reduction of aroyl chlorides. We reason that the heteroleptic Cu(dmp)(BINAP)BF4 performs dual role: reduction of aroyl chlorides and rapid capture of transient radical of type VIII to prevent competitive cyclization. Finally, it is understood that the ultimate proof of the mechanistic proposal would be the isolation of a Cu(III)-intermediate along the reaction pathway, which represents a great challenge given the rapid reductive elimination that can take place to yield the ATRA product with concurrent regeneration of the Cu(I)photocatalyst.