Nickel-Catalyzed trans-Carboamination across Internal Alkynes to Access Multifunctionalized Indoles

Abstract

A Ni-catalyzed reaction was developed for the synthesis of multifunctionalized indoles. The reaction proceeded through oxidative cyclization of the Ni(0)/P^N complex with an enyne system, 2-alkynyl anilinoacrylate, to provide a nickelacycle intermediate. The trans-carboamination around the internal alkyne was achieved by syn/anti-rotation of the Ni-carbenoid intermediate formed by C–N bond cleavage of the nickelacycle, and 3-alkenylated indoles were formed by C–N bond-forming reductive elimination. Notably, the synthesized indoles could be successfully transformed to functionalized carbazoles.

Nickel‐Catalyzed Acyl Group Transfer of o‐Alkynylphenol Esters Accompanied by C−O Bond Fission for Synthesis of Benzo[b]furan

“…The other plausible path based on a proposed mechanism by Cho's report would begin with oxidative cyclization on Ni(0) to forge a CÀ C bond between ester and alkyne. [14] The β-oxygen elimination of intermediate III gives zwitterionic intermediate IV. In the path B, which is analogous mechanism of Cho's report, sequential rotation around CÀ C bonds occurs to form the intermediate VII via the intermediates V and VI.…”

Diastereoselective [2+2+1] Hydrative Annulation of Phenol‐Linked 1,6‐Enynes with Acetylenes Through Rhodium Catalysis: A Rapid Access to Cyclopenta[b]benzofuranols

“…Recently, Arisawa et al [6b] . and Cho et al [6a] . reported a similar but less expensive nickel catalyzed cyclization with concomitant O/N‐acrylate group migration through a rare Ni‐carbenoid intermediate.…”

1,2-Difunctionalizations of alkynes entailing concomitant C–C and C–N bond-forming carboamination reactions

“…Nickel-catalyzed trans -carboamination of internal alkynes was studied by Cho and co-workers for the facile synthesis of highly substituted indole motifs ( Scheme 54 ). 68 Reaction of various 2-alkynyl anilino acrylates 90 with 10 mol% each of Ni(cod) 2 and PyPhos furnished the required indoles 91. Various indole derivatives were synthesized with good to excellent yield.…”