Controllable synthesis of benzoxazinones and 2-hydroxy-3-indolinones by visible-light-promoted 5-endo-dig N-radical cyclization cascade

Brønsted acid–catalyzed asymmetric dearomatization for synthesis of chiral fused polycyclic enone and indoline scaffolds

“…2B, middle) (54). Inspired by the above results and by our recent work on developing homopropargyl amides for N-heterocycle synthesis (55)(56)(57)(58), we envisioned that the reaction of homopropargyl amines with chiral BAs would deliver chiral VQM intermediates, which could be further attacked by intramolecular nucleophiles such as phenols and indoles to generate the axially chiral cyclohexadienone intermediates and centrally chiral imine intermediates, followed by BA-catalyzed intramolecular nucleophilic addition to eventually afford the centrally chiral fused polycyclic N-heterocycles (Fig. 2B, right).…”

Facile access to 2-hydroxy-2-substituted indole-3-ones via a copper-catalyzed oxidative cyclization of 2-arylethynylanilines

“…17 Ye described a controllable synthesis of C2-tertiary N -substituted 2-hydroxy-indol-3-ones by the visible-light-promoted 5 -endo-dig N -radical cyclization of o -ethynylanilines. 18 However, the majority of these approaches suffer from a narrow substrate scope, harsh conditions and/or low yields, which renders these approaches less efficient and attractive (Scheme 1). Therefore, more convenient, efficient and sustainable synthetic alternatives for the assembly of C2-quaternary 2-hydroxyindoxyls from readily available starting materials are still highly desirable.…”

Controlled Photochemical Synthesis of Substituted Isoquinoline-1,3,4(2H)-triones, 3-Hydroxyisoindolin-1-ones, and Phthalimides via Amidyl Radical Cyclization Cascade

“…In recent years, the proton-coupled electron transfer (PCET) process has been used as an alternative method to generate amidyl NCRs via direct N–H bond cleavage. − In addition, the direct generation of NCRs via N–H bond cleavage followed by addition to C–C unsaturated bonds could serve as a very powerful synthetic strategy to construct selective 5 -exo-dig /6 -endo-dig cyclizations to synthesize many N-heterocyclic natural products. − Compared to N-radicals addition to alkenes, the N-radicals addition to alkynes via N–H bond cleavage is very limited, presumably because of the strong bond-dissociation energy and instability of vinyl radicals resulting from radical additions, as well as the lack of an efficient strategy to balance N-radical formation and cyclization. − Ye et al reported a controlled radical cascade cyclization of benzoxazinones and 2-hydroxy-3-indolinones via intramolecular N-radical addition to alkynes using Iridium as a photoredox catalyst (Scheme B) . To date, controlled N-radical addition to alkynes has not been explored more in the literature.…”

“…Next, in a tunable reaction, the 2a / 2b is reacted in the presence of the Acr + -Mes photocatalytic cycle to generate the intermediate β-carbonyl alkoxyl radical 7 . The alkoxyl radical 7 undergoes a β-carbonyl-C­(sp 3 ) bond cleavage to afford desired product 2c and acyl radical 8 . , Further, the acyl radical 8 is quenched by • OH to yield the corresponding acid 2c′ . On the other hand, when R 1 = H; R 2 = alkyl alkynes, the amidyl radical 3 undergoes radical addition to alkynes via 6- endo-dig cyclization to afford cyclized vinyl radical 9 due to the stability of the cyclic benzyl radical.…”