Dearomatizing [2+2+1] Spiroannulation of Indoles with Alkynes

Abstract

A palladium-catalyzed dearomatizing [2+2+1] spiroannulation of indoles with two molecular internal alkynes is developed in the presence of Cu(OAc) 2 /O 2 as the oxidant, in which a domino sequence including C−H activation of indole followed by consecutive Heck reactions is involved. A range of 3,3′-spiroindolines bearing tetrasubstituted cyclopentadiene moieties and exocyclic C�C bonds at C2 are obtained in moderate to excellent yields.

Rhodium(iii)-catalyzed mild and regioselective dearomative spirocyclization of 2-aryl-3-nitrosoindoles with alkynes

“…Obviously, the intermolecular version using separate substrates provides convenience and diversity, but also introduces a challenge in regioselectivity. 11,12 Moreover, a mild reaction, being independent of stoichiometric oxidant or reductant, is also desirable. 2-Aryl-1-methyl-3-nitrosoindoles are easily prepared nitrosation derivatives from 2-arylindoles (Scheme 1, right-down figure).…”

Nickel-Catalyzed Enantioselective Dearomative Heck-Reductive Allylic Defluorination Reaction of Indoles

“…It then undergoes migration insertion across the C2–C3 double bond of indoles to generate alkyl-M species at the C3-position, which is subsequently captured by external nucleophiles or terminated by β-H elimination. A number of research groups including ours have made great achievements in this intriguing field. − Many enantioselective variants toward dearomatization reactions of indoles have been intensively developed thanks to the rich availability of chiral ligands . Of particular note, the cascade Heck-anionic capture reactions with different nucleophiles enable the difunctionalization of indoles, providing various indoline derivatives bearing vicinal stereocenters with diversified functional groups.…”