A metal‐free visible light promoted three‐component facile synthesis of 4‐oxo‐tetrahydroindoles in ethanol–water

Abstract

A mild and efficient visible light–mediated one‐pot multicomponent tandem approach to construct 4‐oxo‐tetrahydroindoles in ethanol–water medium at room temperature has been described. The characteristics of reported methodology are the utilization of visible light, an ideal source of energy to generate CC and CN bonds from commercially available substrates namely dimedone, phenacyl bromides, and amines. The presented protocol is highly compatible for developing 4‐oxo‐tetrahydroindole derivatives with improved selectivity and high yields. Moreover, metal‐free synthesis, environmental friendly solvent, easy workup process, high atom economy, cost‐effectiveness, short reaction time, and broad substratescope are the major advantages of reported protocol.

Recent Developments on Catalyst‐Free, Visible‐Light‐Triggered Synthesis of Heterocyclic Scaffolds and Their Mechanistic Study

“…[24] Ansari et al reported a highly efficient visible lightmediated one-pot strategy for the synthesis of highly functionalized 4-oxo-tetrahydroindoles (7) by the reaction of dimedone (4), phenacyl bromide (5) and aromatic amines (6) in ethanol : water medium at room temperature without any catalyst (Scheme 3). [25] During the screening of light sources and intensities, 22 W CFL was found to be the best source of light with product yield of 92 % within a short reaction time (3.5-4 hours) and only a trace amount of the product was obtained when the reaction was carried out in the absence of light even after 10 hours which confirmed the vital role of light. Initially, the CÀ Br bond of phenacyl bromide (5) underwent homolytic cleavage in presence of visible light to generate a radical 4 A, which further reacted with an excited form of dimedone (4) to form a stable intermediate 4 B.…”

Synthesis andIn vitro‐In silicoEvaluation of Thiazolo‐triazole Hybrids as Anticancer Candidates

“…Taking inspiration from our earlier work, [5,6,[21][22][23] herein, we have synthesized some of the thiazolo[3,2-b]-[1,2,4]triazoles 6 a-t using visible light as a green energy source and water as a solvent. [24][25][26] Visible-light photocatalysis provides additional merits to the reaction condition such as: high yields, inexpensive and readily available visible-light sources, simple workup procedures, environmentally benign reaction conditions, efficient synthesis with safety and sustainability. Starting materials, 1,3-diketones 1 was prepared according to the conventional claisen condensation reaction, [27] however, 3mercapto-[1,2,4]triazoles 5 were prepared as per the literature multistep procedure [28] via the intermediacy of hydrazides, which on treatment with thiocyanate salt and refluxing in basic medium afforded cyclized 3-mercaptotriazole derivatives.…”

“…Taking inspiration from our earlier work, [5,6,21–23] herein, we have synthesized some of the thiazolo[3,2‐ b ]‐[1,2,4]triazoles 6 a – t using visible light as a green energy source and water as a solvent [24–26] . Visible‐light photocatalysis provides additional merits to the reaction condition such as: high yields, inexpensive and readily available visible‐light sources, simple workup procedures, environmentally benign reaction conditions, efficient synthesis with safety and sustainability.…”

Visible-light induced three-component reaction for α-aminobutyronitrile synthesis by C–C bond formation using quantum dots as photocatalysts

“…Because of their high atom efficiency, simplified reaction procedures and shortened reaction times, they represent valuable synthetic strategies. 33–37 In recent years, multicomponent reactions have been successfully combined with photoredox catalysis, and a series of new synthetic methods have been developed. 38–42…”

“…Because of their high atom efficiency, simplified reaction procedures and shortened reaction times, they represent valuable synthetic strategies. [33][34][35][36][37] In recent years, multicomponent reactions have been successfully combined with photoredox catalysis, and a series of new synthetic methods have been developed. [38][39][40][41][42] Nitriles are prevalent structural motifs found in a number of natural products, synthetic pharmaceuticals, and functional materials.…”