Synthesis of Indoles through Palladium-Catalyzed Three-Component Reaction of Aryl Iodides, Alkynes, and Diaziridinone

Abstract

The three-component reaction of aryl iodides, alkynes, and diaziridinone is described. The reaction provides an innovative synthetic approach for indoles. The approach features high efficiency, broad substrate scope, and excellent regioselectivity. C,C-Palladacycles should act as the intermediates. The C,C-palladacycles are obtained from simple aryl halides and alkynes and then reacted with diaziridinone to afford indoles.

Recent Advances in Palladium-Catalyzed Bridging C–H Activation by Using Alkenes, Alkynes or Diazo Compounds as Bridging Reagents

“…34 The same group also discovered that intermediate 88 could be trapped by di-tert-butyldiaziridinone 49 to give substituted indoles 90 bearing a tert-butyl group on the nitrogen atom (Scheme 19, b). 35 More recently, Habibi and Jafarpour used simple and readily accessible anilines as nitrogen sources to react with palladacycle 88, giving N-aryl-substituted indoles 90′ in a highly efficient manner (Scheme 19, c). 36 By using CH 2 Br 2 as the reaction partner, Zhang and co-workers uncovered a valuable method for the preparation of benzofulvenes 91 through the alkylation of intermediate 88 (Scheme 19, d).…”

Synthesis of Benzimidazoles through Palladium‐Catalyzed Amination of 2‐Iodobenzimines with Diaziridinone

“…On the other hand, the Shi group demonstrated that diaziridinone exhibits high reactivity towards C , C ‐palladacycles (Scheme ) ,. Inspired by this pioneering work, our group developed amination reactions of C , C ‐palladacycles derived from 2‐iodobiphenyls or formed through the reaction of aryl iodides and alkynes (Scheme ) ,. We envisioned that diaziridinone might also react with the C , C ‐palladacycles derived from 2‐iodobenzimines.…”

Pd-Catalyzed Alkyne Insertion/C–H Activation/[4 + 2] Carboannulation of Alkenes to the Synthesis of Polycyclics

“…On the basis of the above mechanistic study and literature precedents, − a plausible catalytic cycle of this reaction was proposed and shown in Scheme . Initially, the oxidative addition of aryl iodide 1a to the active Pd(0) generates the aryl Pd­(II) species A , which inserts the diphenylacetylene 2a to form the intermediate B .…”

“…In this reaction, the C–H activation was triggered by an in situ generated alkenylpalladium species via the Pd-catalyzed cross-coupling reaction of aryl iodides and alkynes. Subsequently, the resulting five-membered C, C-palladacycle species were added across the alkenes, providing a unique approach to access diversified polycyclics in good efficiency (Figure c). Setting the potentially competitive benzannulation between the five-membered C, C-palladacycles and alkynes or aryl halides is a key to the success of this tandem reaction.…”