Pd-PEPPSI-IPent^Cl: a new highly efficient ligand-free and recyclable catalyst system for the synthesis of 2-substituted indoles via domino copper-free Sonogashira coupling/cyclization

Abstract

One pot synthesis of 2-substituted indolesviaSonogashira coupling (without a copper catalyst) followed by intermolecular cyclization using Pd-PEPPSI-IPentCl.

2‐hydroxyethyl‐substituted (NHC)PdI2(pyridine) (Pd‐PEPPSI) Complexes: Synthesis, Characterization and the Catalytic Activity in the Sonogashira Cross‐coupling Reaction

“…Alternatively, the use of Pd‐PEPPSI complexes as catalysts in Sonogashira cross‐coupling reactions largely prevents these disadvantages. There are a few studies in the literature that Pd‐PEPPSI complexes are used as catalysts in the Sonogashira cross‐coupling reaction ,. Thus, our study group synthesized a new series of 2‐hydroxyethyl substituted Pd‐PEPPSI complexes and examined the catalytic activities of these complexes in Sonogashira cross‐coupling reactions.…”

Synthesis of 2‐Substituted Indoles by Pd‐Catalyzed Reductive Cyclization of 1‐Halo‐2‐nitrobenzene with Alkynes

“…Subsequently, complex B forms by the ligand exchange reaction of complex A with terminal alkyne. Then the reductive elimination of B generates the Sonogashira coupled product C. In the presence of active Pd(0) species, Zn, TMSCl and base Et 3 N, nitro group of product C could be reduced into amino group [26e] or other reduced species such as N-phenyl hydroxylamine, nitrosobenzene [6a,b] or azobenzene [26a,d] followed by the πcoordination to form complex D. This complex undergoes deprotonation to provide π-coordinated complex E. [5d] The protonation of complex E results in desired indole product F. [27] Scheme 4. Gram Scale Experiment.…”

Recent Development in Palladium-Catalyzed Domino Reactions: Access to Materials and Biologically Important Carbo- and Heterocycles

“…It showed a greater performance in the cascade reaction of various 2-bromo anilines with different terminal aromatic acetylenes under mild (60 °C) and green conditions (ethanol:​water) even in the absence of a copper catalyst and an inert atmosphere (Scheme ). The catalyst was recyclable and could be reused up to six cycles …”

“…The catalyst was recyclable and could be reused up to six cycles. 84 Diindolylmethanes (DIMs), a subfamily of indoles, are beneficial antibacterial, antifungal, anti-androgenic, anticancer, growth-promoting, and anti-implantation drugs. In addition, synthetic DIMs are also known to act as dyes and colorimetric sensors.…”