Photocatalytic deoxygenative carboimination of unstrained γ,δ‐unsaturated oximes with π‐acceptors including trifluoromethyl alkenes, 1‐trifluoromethyl‐1,3‐butadienes, gem‐difluoroalkenes, acrylates, and styrenes has been achieved which provides an efficient and mild approach to construct structurally diverse and highly functionalized pyrrolines with good functional group tolerance. Importantly, upon utilization of trifluoromethyl alkenes as the coupling partners, the developed protocol not only allows the introduction of the extremely valuable gem‐difluoroalkene functionality and pyrroline moiety into one molecule, but could also further transform the resulting gem‐difluoroalkene‐functionalized pyrrolines to the architecturally intriguing indolizine alkaloids via oxidation/reduction and sequential C−F bond cleavage. The mechanistic studies indicated that a free‐radical and anionic process was probably involved in this photocatalytic deoxygenative transformation.
A chemodivergent photocatalytic approach to 1-pyrrolines and 1-tetralones from alkyl bromides and vinyl azides has been developed through chemoselectively controllable intermolecular [3 + 2] and [4 + 2] cyclization. This photoredox-neutral two-component protocol involves intermolecular radical addition and switchable distal C(sp3)–H functionalization enabled by iminyl radical-mediated 1,5-hydrogen atom transfer. Meanwhile, chemoselectivity between C(sp3)–N bond formation and C(sp3)–C(sp2) bond formation is precisely switched by photocatalysts (Ru(bpy)3(PF6)2 vs. fac-Ir(ppy)3) and additives (base vs. acid).
We report an example of non‐dearomative trifunctionalizing ipso‐spirocyclization of unactivated alkenes through photoredox‐catalyzed, nitrogen‐radical‐triggered cyclization‐trapping‐translocation‐cyclization cascade, providing a single‐step modular access to spiroaminal frameworks through the sequential formation of one C−C bond and two geminal C−N bonds. The developed protocol utilizes not only internal and terminal olefinic oxime esters, but also olefinic amides as nitrogen radical precursors, and features a broad substrate scope, wide functional group compatibility, easy scalability, and potential for product derivatization and late‐stage functionalization of bioactive estrone derivatives. Importantly, the mechanistic studies including DFT calculations indicate that the photocatalytic trifunctionalizing ipso‐spirocyclization undergoes a radical relay cascade of intramolecular 5‐exo‐trig cyclization, intermolecular radical trapping, 1,5‐hydrogen atom transfer, and sequential 5‐endo‐trig cyclization, which provides another reaction mode of alkenes.
Carbon-carbon cleavage | Alkoxy radical | Copper-catalyzed | 1,1-Disubstituted alkenes | Sulfonyl hydrazides Alkoxy radical-mediated carbon-carbon bond cleavages have emerged as a powerful strategy to complement traditional ionic-type transformations. However, carbon-carbon cleavage reaction triggered by alkoxy radical intermediate derived from the combination of alkyl radical and dioxygen, is scarce and underdeveloped. Herein, we report alkoxy radical, which was generated from alkyl radical and dioxygen, mediated selective cleavage of unstrained carbon-carbon bond for the oxysulfonylation of 1,1-disubstituted alkenes, providing facile access to a variety of valuable β-keto sulfones. Mechanistic experiments indicated alkoxy radical intermediate that underwent subsequent regioselective β-scission might be involved in the reaction and preliminary computational studies were conducted to provide a detailed explanation on the regioselectivity of the CC bond cleavage. Notably, the strategy was successfully applied for constructing uneasily obtained architecturally intriguing molecules.
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