Visible-Light-Promoted Tandem Annulation of N-(o-Ethynylaryl)acrylamides with CH₂Cl₂

Abstract

A novel tandem annulation of N-(o-ethynylaryl)acrylamides, with CHCl as a one-carbon unit, for the divergent synthesis of cyclopenta[c]quinolin-4(5H)-ones and benzo[j]phenanthridin-6(5H)-ones, which relies on the substitution effect of the 2 position of the acrylamide moiety, is described. Promoted by the visible-light photoredox catalysis, this reaction allows the formation of multiple chemical bonds through multiple C-Cl/C-H functionalization and [2 + 2 + 1] annulation cascades.

Recent Developments in the Polychloroalkylation by Use of Simple Alkyl Chlorides

“…In 2018, our group reported the construction of a cyclopenta[ c ]quinoline architecture and benzo[ j ]phenanthridin‐6(5 H )‐ones by visible light photoredox catalysis (Scheme 39). [37] The use of dichloromethane as one carbon source can easily convert to different functional groups, such as CHO, Cl and CHCl 2 , by the annulation cascades of N ‐(o‐Ethynylaryl)acrylamides or 2‐Benzyl‐ N ‐( o ‐(arylethynyl)aryl)acrylamides. It is worth noting that the methodology can obtain the desired products without light in 35% yield, indicating that thermal decomposition of aryldiazonium salts can also produce dichloromethyl radical in the absence of [Ir(ppy) 2 dtbbpy]PF 6 and visible light.…”

Reaction Medium as the Installing Reservoir for Key Functionalities in the Molecules

“…Recently, Liu et al . (2018) has utilized DCM as a one carbon source and chlorinating agent for the cyclopenta‐quinolinones and benzo‐phenanthridinones (Scheme ) . The reaction starts with the quenchinh of visible light induced excited state [Ir III ]* species by ArN 2 BF 4 to form the [Ir IV ] species and the aryl radical intermediate.…”

Recent Advances in Radical‐Enabled Bicyclization and Annulation/1,n‐Bifunctionalization Reactions

“…This reactionp roceeded smoothly in CH 2 Cl 2 with 2.5 mol %[ Ir(ppy) 2 dtbbpy]PF 6 as a photocatalyst, 5.0 equivalents of Na 2 CO 3 as ab ase, 4.0 equivalents of water as ar eaction partner,a nd 5.0 equivalentso f4 -MeOC 6 H 4 N 2 BF 4 .T his transformation allowedf or ar ange of CÀ Cl/CÀHf unctionalization and bicyclization cascade reactions, thereby delivering3 2examples of fused quinolones in 50-91 % yields (Scheme 8a). [20] AlthoughC H 2 Cl 2 is commonly regarded as an inactivec hemical entity and is routinely used as ar eaction solvent, in this reaction, CH 2 Cl 2 functioned as an unpredictable reactions ubstrate. According to the proposed mechanism, the CCHCl 2 radical intermediate (21), which is generated by SET,u ndergoes ar adical-addition-cyclization reaction to afford vinyl radical intermediate 22.S imilar to the previous report( see above), the R 3 group is key to controlling the chemoselectivity of this reaction.…”

“…This reaction proceeded smoothly in CH 2 Cl 2 with 2.5 mol % [Ir(ppy) 2 dtbbpy]PF 6 as a photocatalyst, 5.0 equivalents of Na 2 CO 3 as a base, 4.0 equivalents of water as a reaction partner, and 5.0 equivalents of 4‐MeOC 6 H 4 N 2 BF 4 . This transformation allowed for a range of C−Cl/C−H functionalization and bicyclization cascade reactions, thereby delivering 32 examples of fused quinolones in 50–91 % yields (Scheme a) . Although CH 2 Cl 2 is commonly regarded as an inactive chemical entity and is routinely used as a reaction solvent, in this reaction, CH 2 Cl 2 functioned as an unpredictable reaction substrate.…”