A Sustainable Synthesis of Functionalized Pyrrole Fused Coumarins under Solvent‐Free Conditions Using Magnetic Nanocatalyst and a New Route to Polyaromatic Indolocoumarins

Abstract

A general and environmentally benign one‐pot method has been developed for the library synthesis of biologically important chromeno[4, 3‐b]pyrrol‐4(1H)‐one derivatives. A three‐component domino condensation of 4‐aminocoumrins, arylglyoxal monohydrates and various nucleophilic substrates, such as, arylamines, malononitrile, ethyl cyanoacetate and cyanoacetamide produced functionalized chromeno[4, 3‐b]pyrrol‐4(1H)‐ones in presence of magnetically separable Fe3O4@SiO2‐SO3H nanoparticles as solid acid catalyst under solvent free conditions. Furthermore, a two‐component condensation of 4‐aminocoumrins and arylglyoxal monohydrates furnished a series of hydroxy functionalized chromeno[4, 3‐b]pyrrol‐4(1H)‐ones under similar reaction conditions. The salient features of the present method are mild reaction conditions, reduced reaction time, elimination of hazardous solvents, good yield of the products, greater substrate scope and use of a magnetically separable and recyclable nanocatalyst. Moreover, it has been observed that a class of chromeno[4, 3‐b]pyrrol‐4(1H)‐one derivatives can be easily converted to biologically important indolo[3, 2‐c]coumarin derivatives in good yield through intramolecular thermal cyclization without using any catalyst.

A decennary update on applications of metal nanoparticles (MNPs) in the synthesis of nitrogen- and oxygen-containing heterocyclic scaffolds

“…The reusability of the Fe 3 O 4 @SiO 2 -SO 3 H MNPs via magnetic separation was found to be altered aer the seventh catalytic run. 213 Previously, they also reported the catalytic use of Fe 3 O 4 @SO 3 H NPs for the synthesis of dihydrofuran-based cyclooctanoids (197) via the dehydration of cyclooctanoids (196) at rt in a shorter reaction time (Scheme 104). 214 Shiri et al reported the use of the same catalyst for the green synthesis of pyrrolo[1,2-a]pyrazines via the threecomponent reaction of ethylenediamine, dimethyl acetylenedicarboxylate, and b-nitrostyrene.…”

Recent Trends in Iron‐Catalyzed Reactions towards the Synthesis of Nitrogen‐Containing Heterocycles

“…(a) Synthesis of pyrroles : A multicomponent synthetic strategy for functionalized pyrrole‐fused coumarins, whereby many of these pyrrolocoumarins are biologically active, was reported . The solid nanocatalyst employed was the magnetically separable Fe 3 O 4 @SiO 2 ‐SO 3 H MNP under solvent‐free conditions.…”

Nicotinic acid‐supported cobalt ferrite‐catalyzed one‐pot synthesis of substituted chromeno[3,4‐b]quinolines

“…Aminocoumarin derivatives have a wide range of biological applications, such as antibiotics, fluorescent markers, melanin‐concentrating hormone receptor antagonist, inducing estrogenic activity, carbonic anhydrase class of inhibitors, and α‐glucosidase inhibitors . Organic compounds containing 4‐aminocoumarin scaffold are synthesized by the reaction of 4‐hydroxycoumarin, ammonia solution, Meldrum's acid, and aromatic aldehydes in the presence of SBA‐15‐SO 3 H; three‐component reaction of 4‐aminocoumarin, arylglyoxal monohydrates, and aromatic amines promoted by KHSO 4 in toluene under reflux condition; three‐component condensation of 4‐aminocoumarin, aldehydes, and ethyl benzoylacetates by POCl 3 in dichloroethane under reflux conditions; three‐component domino condensation of 4‐ aminocoumarins, arylglyoxal monohydrates, and various nucleophilic substrates, such as arylamines, malononitrile, ethyl cyanoacetate, and cyanoacetamide‐produced functionalized chromeno[4,3‐ b ]pyrrol‐4(1 H )‐ones in the presence of Fe 3 O 4 @SiO 2 ‐SO 3 H nanoparticles as a solid acid catalyst under solvent‐free conditions; oxidative aromatization of tetrahydrochromeno[4,3‐ b ]quinoline derivatives by nitric acid at ambient temperature; two‐component coupling of 4‐aminocoumarin and α,β‐unsaturated nitroalkene catalyzed by PEG–SO 3 H; three‐component reaction of phenyl glyoxal, dimedone, and 4‐amino coumarin to afford disubstituted chromeno[4,3‐ b ]pyrrole‐4(1 H )‐one derivatives catalyzed by I 2 /dimethyl sulfoxide (DMSO); synthesis of coumarin fused to highly decorated indenodihydropyridyl and dihydropyridyl derivatives in the presence of (±)lactic acid/ethyl‐ l ‐lactate at 100 °C; and synthesis of chromeno[4,3‐ b ]quinoline derivatives in the presence of catalytic amounts of Cu(II)–Schiff base/SBA‐15 by condensation of arylaldehydes with 1,3‐cyclohexadione and then treating the obtained intermediates with 4‐aminocoumarin in an autoclave at 200 °C . Despite the potential utility of these methods, some suffer from disadvantages such as long reaction times, low yields, high reaction temperature, and the use of more corrosive catalyst.…”