Kamal K. Kapoor

SbCl3‐Al2O3–Catalyzed, Solvent‐Free, One‐Pot Synthesis of Benzo[b]1,4‐diazepines

Abstract This article explores the use of antimony(III) chloride adsorbed on neutral alumina as an efficient catalyst for the one‐pot synthesis of benzo[b]1,4‐diazepines (83–94%) under solvent‐free conditions. The process is easy, efficient, ecofriendly, and economical.

Alum-Catalyzed One-Pot Solventless Synthesis of 1,5-Benzodiazepines

Alum [KAl(SO4)2∙12H2O] was found to be an efficient, non-toxic, cheap, and environmentally benign catalyst for the synthesis of 1,5-benzodiazepines, in good to excellent yields, from the condensation of 1 mole of o-phenylenediamine with 2 moles of ketone under solvent-free conditions.

Active methylenes in the synthesis of a pyrrole motif: an imperative structural unit of pharmaceuticals, natural products and optoelectronic materials

Pyrrole is one of the most important azaheterocycles, due to its wide range of applications in pharmaceuticals and optoelectronic materials, coupled with its utility as an intermediate in natural products. For several decades, realisation of the scope and potential of this heterocyclic system in both the pharmaceutical and materials industries, has sparked new efforts in finding more efficient synthetic methods for the preparation of pyrrole compounds. Inspired by the importance of this system, herein, we report a review on pyrrole based pharmaceuticals, natural products and optoelectronic materials. Synthetic approaches to pyrrole from active methylenes are also reviewed together with novel reports from our laboratory recently (till 2015).

KHSO4 · H2O/SiO2‐Catalyzed, One‐Pot, Solvent‐Free Synthesis of Pyrazolines, Tetrahydrocarbozoles and Indoles using Microwave Irradiation

Abstract A new high‐yielding, operationally simple, solvent‐free, and mild method for preparation of pyrazolines, tetrahydrocarbazoles, and indoles has been developed using KHSO4 · H2O impregnated on SiO2. The reactions have been probed under microwave irradiation (MWI), and ultrasonic and thermal conditions, employing different solid supports. The data revealed that KHSO4 · H2O impregnated on SiO2 under MWI provides the best yields in a shorter time under solvent‐free reaction conditions.

Zinc-Mediated Reductive Cyclodimerization of α,β-Unsaturated Aryl Ketones Under Aqueous Conditions

Zinc-mediated reductive cyclodimerization of α,β-unsaturated aryl ketones produces 3,4-trans-diarylcyclopentanols 2 regio- and stereoselectively in good yields in a 1:4 (v/v) mixture of saturated aqueous NH4Cl and tetrahydrofuran at room temperature.

Anticancer potential of labdane diterpenoid lactone “andrographolide” and its derivatives: a semi-synthetic approach

Natural products have been a great source of pharmaceuticals since ages. Vast screening of natural products from different sources has led to the discovery of plethora of chemotherapeutic drugs and other compounds for the betterment of human life. Several bioactive entities have been generated by the structural modifications of the natural products or by using the natives as key models in synthetic chemistry. Nonetheless, a number of natural compounds with potential bioactivities remain unexploited in the medicinal field due to their stringent chemical properties. Andrographis paniculata Nees., a traditional medicinal herb from family Acanthaceae is known for its multiple pharmacological activities. It’s major bioactive constituent “andrographolide”, possesses promising anticancer potential and is one such unexploited treasure. The architecture of the molecule consists of an α-alkylidene γ-butyrolactone moiety, two olefin bond [Δ8(17) and Δ12(13)], three hydroxyls at C-3, C-19, and C-14 and highly substituted trans decalin. Of the three hydroxyl groups, one is allylic at C-14, and the others are secondary and primary at C-3 and C-19, respectively. By modification of the above structural features a number of andrographolide derivatives have been synthesized. The intricacy of the molecule has always been a constraint in developing a commercialized drug, nevertheless the efforts in this direction via synthetic chemistry are still continuous and prominent. The present review highlights the chemistry and anticancer activity of andrographolide. It discusses the limitations of the molecule as a pharmacological agent. Modifications in the key molecule along different moieties has been discussed which might lead to desirable bioactive molecules. The compiled information will be helpful in further developing specific modifications in andrographolide moiety which will have significant contribution in semi synthesis of anti-cancer agents.

Alum-Catalyzed Domino Synthesis of 12-Substituted-8,9,10,12-tetrahydrobenzoxanthen-11-ones Under Solvent-Free Conditions

Abstract Alum is found to catalyze efficiently the one-pot, three-component condensation of aldehydes, α/β-naphthol, and dimedone to afford various 12-substituted-8,9,10,12-tetrahydrobenzoxanthen-11-ones in excellent yields. The use of alum catalyst and the solvent-free conditions make this method simple, convenient, eco-friendly, and cost-effective. GRAPHICAL ABSTRACT

One-pot, Solvent-free Cascade Michael-reductive Cyclization Reaction for the Synthesis of Ethyl 3,5-disubstituted-1H-pyrrole-2-carboxylates Under Microwave Irradiation

An efficient, one-pot, solvent-free synthesis of ethyl 3,5-disubstituted-1H-pyrrole-2-carboxylate is achieved by a reaction of 1,3-disubstituted propen-2-one and ethylnitroacetate, in presence of diethylamine (Et2NH) and triethyl- phosphite (P(OEt)3) under microwave (MW) irradiation via cascade Michael-reductive cyclization. The mechanistic out- come of the reaction has also been described. This protocol establishes an easy access to disubstituted-1H-pyrrole-2- carboxylates in one pot.

Bi(NO3)3–Al2O3-Mediated Efficient Synthesis of 4-Aryl-2,6-dicoumarinylpyridines Under Solventless Conditions

A new efficient and eco-friendly methodology has been developed for the synthesis of 4-aryl-2,6-dicoumarinylpyridines from coumarinylchalcones and urea, using Bi(iii) nitrate–Al2O3 as catalyst. Coumarinylchalcones were in turn prepared from salicylaldehyde and ethylacetoacetate by the tandem reaction with aldehydes on the surface of Bi(iii) nitrate–Al2O3 in the presence of the co-catalyst Zn(ii) chloride.

Reaction of 3-(2-nitrophenyl)-1-arylprop-2-en-1-ones with triethylphosphite in microwave revisited: One-pot synthesis of 2-aroylindoles and 2-arylquinolines

ABSTRACT One-pot synthesis of 2-aroylindoles and 2-arylquinolines has been achieved by the reductive cyclization of 3-(2-nitrophenyl)-1-arylprop-2-en-1-ones with triethylphosphite [P(OEt)3] under microwave irradiation. The formation of 2-arylquinolines by this method is unprecedented. GRAPHICAL ABSTRACT