Michael Initiated Ring Closure (MIRC) reaction on in situ generated benzylidenecyclohexane-1,3-diones for the construction of chromeno[3,4-b]quinoline derivatives

The Chromenopyridine Scaffold: A Privileged Platform in Drug Design

The chromenopyridine scaffold represents an important class of heterocyclic compounds exhibiting a broad spectrum of biological properties. This review describes novel and efficient procedures for the synthesis of this scaffold. Herein, several methods were detailed and grouped according to their starting material (e.g., salicylaldehydes, chromones, chromanones and coumarins) and respective biological activity, when reported. This review highlights the potential of the reported synthetic strategies for preparing chromenopyridine derivatives with promising biological activity, paving the way for further developments in drug discovery.

Synthetic utility of biomimicking vanadium bromoperoxidase and n-tetrabutylammonium tribromide (TBATB) in organic synthesis

Nature has established a broad spectrum of methods to introduce halogen atoms in organic compounds. Recent developments have revealed that haloperoxidases are one of the major sources responsible for incorporating bromines to produce bromoorganics in nature. Pioneering studies of numerous researchers have unravelled the details of haloperoxidases, mainly vanadium dependent enzyme bromo- and iodo-peroxidases, including reaction mechanism, kinetics and especially biomimicking studies. In this review, we initially have described the scope of biomimicking vanadium bromoperoxidase in producing the bromonium ion and its further utilisation in conducting oxidative bromination or cleavage of various organic molecules. Moreover, by biomicmicking, the synthesis of OATB and the synthetic utility of various organic ammonium tribromides (OATBs) have been discussed. Among such OATBs, n-tetrabutylammonium tribromide (TBATB) has been explored for bromination of organic molecules as well as in the facile removal of several protecting groups and as a potential catalyst in various synthetic transformations. This review attempts to compile a myriad of reactions concerning the catalytic activity of vanadium bromoperoxidases and the usefulness of various OATBs, particularly with special emphasis on TBATB in various organic transformations.

One-pot, Multicomponent Synthesis under Microwave Conditions of New Imidazole and Acridine Benzamido Acetic Acid Derivatives

Starting from 4-aminohippuric acid (AHA), two novel series of heterocyclic compounds of pharmaceutical interest have been synthesised by one-pot, multicomponent reactions under microwave conditions. Reaction of AHA with various aldehydes and benzil in (1:1) EtOH/acetic acid in the presence of ammonium acetate yielded 1,2,3,5-tetra-arylated imidazole derivatives, whereas a solvent-free reaction of AHA with various aldehydes and dimedone (2 equiv.) in the presence of p-TSA yielded 4,9-diarylated 1,8-dioxo-decahydroacridine derivatives. These reactions produced good yields in short reaction times with an easy work-up, and purification of products was achieved by simple recrystallisation.

One-Pot, Three-Component Condensation Reaction for the Synthesis of Novel Chromeno[3,2-f]Quinoline Derivatives

A one-potsynthesis of novel chromeno[3,2- f]quinoline derivatives has been achieved with good yields through Michael Initiated Ring Closure by employing a three-component condensation of an aromatic aldehyde, 5,5-dimethylcyclohexane-1,3-dione and 6-hydroxyquinoline in the presence of a catalytic amount of Et3N in ethanol under reflux conditions. The salient features of this protocol are a simple reaction procedure, good yields, avoidance of an aqueous work-up and simple purification by recrystallisation.

An efficient five-component synthesis of thioether containing dihydropyrano[2,3-c]pyrazoles: a green domino strategy

A one-pot, five component domino synthesis of novel thioether containing dihydropyrano[2,3-c]pyrazoles under solvent-free and catalyst-free conditions is demonstrated.

Synthesis of fused oxazole-containing coumarin derivatives via oxidative cross coupling reaction using a combination of CuCl2 and TBHP

Various fused oxazoles containing coumarin derivatives were synthesized via an oxidative cross coupling reaction by employing 20 mol% CuCl₂ as the catalyst and TBHP as an oxidant.

Coumarin heterocyclic derivatives: chemical synthesis and biological activity

This review highlights the broad range of science that has arisen from the synthesis of coumarin-linked and fused heterocycle derivatives. Specific topics include their synthesis and biological activity.

Synthesis of Unsymmetrical Sulfides and Their Oxidation to Sulfones to Discover Potent Antileishmanial Agents

Unsymmetrical sulfides were first synthesized using combinations of a 1,3-dicarbonyl, an aromatic aldehyde and a thiol in the presence of 10 mol % ethanolic piperidine. These sulfides derivatives were subsequently converted into corresponding sulfones via oxidation in the presence of m-chloroperoxybenzoic acid (m-CPBA) at ice-bath to room temperature. The former reaction was achieved at room temperature through one-pot three-component. The later was obtained in good yields using mild reaction conditions with flexibility in choice from a range of substrates. The antimicrobial properties of the newly synthesized sulfone derivatives were investigated against the protozoan parasite, Leishmania donovani, a causative agent of visceral leishmaniasis (VL). Nine sulfone derivatives were found to be efficacious and exhibited significant antimicrobial activity. Further, these compounds were nontoxic on murine peritoneal macrophages thus eliminating potential cytoxicity in the host cells. These compounds may be indicated as potential leads in the treatment of visceral leishmaniasis.

A one-pot three-component reaction involving 2-aminochromone in aqueous micellar medium: a green synthesis of hexahydrochromeno[2,3-b]quinolinedione

An efficient and green synthesis of hitherto unreported 11-(chromen-3-yl)-8,8-dimethyl-8,9-dihydro-6H-chromeno[2,3-b]quinoline-10,12(7H,11H)-dione has been accomplished by a three-component reaction involving 2-aminochromone, chromone-3-carbaldehyde, and 5,5-dimethyl-1,3-cyclohexanedione (dimedone) in 0.5 M aqueous SDS solution. The mechanism of the reaction has been studied by isolating the reaction intermediate. This methodology features eco-friendly reaction conditions, a simple working procedure, high atom-economy and high efficiency in product formation.

Metal-free domino one-pot protocols for quinoline synthesis

Metal-free domino one-pot protocols for quinoline synthesis have been reviewed.

Oxidative cross coupling reaction mediated by I2/H2O2: a novel approach for the construction of fused thiazole containing coumarin derivatives

Various 2-phenyl-4H-chromeno(3,4-d)thiazol-4-one derivatives have been synthesized through C–H bond activation using sodium sulfide as a source of sulfur atoms and by employing I₂ as a catalyst and H₂O₂ as the terminal oxidant.