Metal-Free Induced Tandem Cyclization of 2‑Aryl‑N‑Methacryloyl Indoles via 1,2-Hydrogen Atom Transfer
Peng Chen1, Wanting Peng1,2, Xingqin Tian1
1Department of Rehabilitation and Pharmacy, Taihe Hospital, Hubei University of Medicine, Hubei Provincial Clinical Research Center for Umbilical Cord Blood Hematopoietic Stem Cells, Shiyan, Hubei 442000, China.
Abstract:
This article reports a photoredox-catalyzed tandem cyclization of 2-aryl-N-methacryloyl indoles via 1,2-hydrogen atom transfer (1,2-HAT) to rapidly synthesize indolo-[2,1-a]-isoquinoline derivatives under mild conditions. This method affords a variety of indolo-[2,1-a]-isoquinoline compounds in good to excellent yields. In contrast to previous reports that relied on transition-metal catalysis or harsh reaction conditions, this strategy offers multiple advantages, including mild and metal-free reaction conditions, a radical tandem reaction mechanism involving a 1,2-HAT process, a wide range of compatible substrates, and excellent tolerance toward functional groups.
Related Concept Videos
Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
Cycloaddition Reactions: Overview
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation


