Free Radical Triggered Convenient Synthesis of Bis(indolyl)methane with Potassium Peroxodisulfate as Catalyst

Abstract

The free radical triggered convenient synthesis of bis(indolyl) methane using various indole and aldehyde derivatives with potassium peroxodisulfate as catalyst under the ambient conditions is developed. This protocol exhibits a wide range of sterically and electronically diverse substrate scope with good to excellent yield (up to 94 %) of the desired product without affecting the bromo, chloro, iodo, nitro, methoxy, and hydroxyl groups. The experimental observation indicates that the reaction follow a radical pathway.

Synthesis of Bis(3‐indolyl)methanes Mediated by Potassium tert‐Butoxide

“…Preparation of these compounds is usually done by addition of aldehydes or ketones to two molecules of indole via acid [5,6] or base catalysis [7] . Furthermore, alternative and more sustainable methods have emerged, based on metal‐catalysed [8,9] and metal‐free reactions [10] . This includes metal‐catalysed carbonylation and alkylation reactions [11–13] and organocatalysed reactions [14] .…”

“… [7] Furthermore, alternative and more sustainable methods have emerged, based on metal‐catalysed[ 8 , 9 ] and metal‐free reactions. [10] This includes metal‐catalysed carbonylation and alkylation reactions[ 11 , 12 , 13 ] and organocatalysed reactions. [14] Other examples also include the use of metal‐free oxidative reactions.…”

Humic acid: A Biodegradable Organocatalyst for Solvent‐free Synthesis of Bis(indolyl)methanes, Bis(pyrazolyl)methanes, Bis‐coumarins and Bis‐lawsones

“…A few protocols are reported in literature using various catalyst and solvent such as enzymes, [21] meglumine, [22] thiamine hydrochloride, [23] graphene oxide, [24] ethyl lactate, [25] sulphated polyborate, [26] Lewis acids, [27–32] Brønsted acids, [33] heteropoly acids, [34–36] solid acids, [37–42] ionic liquids, [43] metal complexes, [44–46] 4‐sulfophthalic acid [47] and Iodine/tert‐Butyl Hydroperoxide [48] . Recently, a number of methodologies have been developed in this field [49–68] . A generalize scheme for the different processes so far reported in literature are drawn in Scheme 1.…”

“…[48] Recently, a number of methodologies have been developed in this field. [49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] A generalize scheme for the different processes so far reported in literature are drawn in Scheme 1. But some of these protocols have many drawbacks like use of toxic metal salts or catalytic systems with expensive reagents, photosensitive catalysts, high catalyst loadings, high temperatures, chromatographic purifications, costly catalyst as well as solvent, time consuming during preparation of catalyst, harsh reaction conditions and hazardous solvent.…”

Utilization of methanol and ethanol for 3,3′-bis(indolyl)methane synthesis through activation of peroxymonosulfate over a copper catalyst

“…The carbonyl radical then interacted with the indole moiety leading to the formation of 3,3′-BIMs following the free radical path shown in Scheme 3(b). 21…”