Domino Relay Olefin Metathesis of Triallyl Oxindole and Indole Precursors to Access Cyclic Indoxyls and Carbazoles

Abstract

We herein disclose domino relay metathesis sequences using triallyl 3-oxindole and indole precursors to access C2-quaternary cyclic pseudooxindole and carbazole ring systems. Triallyl 3oxindoles undergo domino ring closing metathesis (RCM) and cross metathesis (CM) to provide C2-spirocyclic 3-oxindoles. Intriguingly, a catalyst specific relay metathesis sequence involving ring closing-ring opening-ring closing and cross metathesis (RC-RO-RC-CM) of these trienes is established to provide fused bicyclic indoxyl dimers in high yields. Further, the CM of indoxyl dimer with methyl acrylate affords a new class of fused monomeric 3-oxindole derivative. Moreover, a domino RCM-CM process of triallyl indoles is demonstrated, enabling a quick access to dihydro-carbazoles and carbazoles.

Editorial: The Catalysis of Ring Synthesis

“…An elegant cascade process towards challenging oligocyclic systems through the combination of a formal anti ‐carbopalladation with a Suzuki cross‐coupling, was devised by the Werz group [9] . A further cascade process by means of an efficient domino relay metathesis sequences using triallyl 3‐oxindole and indole precursors to access fused bicyclic indoxyl dimers and carbazole derivatives is described in the Communication by the Dash group, [10] while a ligand‐ and additive‐free process developed by the Hoover group allows a straightforward aerobic cobalt‐catalyzed synthesis of 2‐aminobenzimidazoles starting from 2‐aminoanilines [11] . An efficient cobalt‐catalyzed carbonylative ring expansion of oxetanes or thietanes under syngas atmosphere route towards γ‐(thio)butyrolactone is presented by the Dong group [12] .…”