A water-mediated and catalyst-free simple protocol for easily accessing a huge array of pharmaceutically interesting and diversely functionalized 5-alkyl/aryl/heteroaryl-10-alkyl/aryl-2,8-dioxo/dithioxo-9,10-dihydropyrido[2,3d:6,5-d′]dipyrimidine-4,6(1H,3H,5H,7H)-dione derivatives 4 (4-1−4-42) and 5,5′-(1,4-phenylene)bis(10-alkyl/aryl-2,8dioxo/dithioxo-9,10-dihydropyrido[2,3-d:6,5-d′]dipyrimidine-4,6(1H,3H,5H,7H)-dione) 4′ (4′-1−4′-8) has been developed based on a one-pot multicomponent reaction between barbituric/N,N-dimethylbarbituric/2-thiobarbituric acids (1), substituted amines (2), and aldehydes (3) under ambient conditions. The salient features of this protocol are the clean reaction profile, use of no added catalyst, water as reaction media, mild reaction conditions at room temperature, energyefficiency, easy isolation of products, no need of column chromatographic purification, high atom-economy and low E-factor, good to excellent yields, and reusability of reaction media.

An ultrasound-assisted, highly efficient, simple, and straightforward protocol for one-pot synthesis of a new series of pharmaceutically relevant and diversely functionalized 7-aryl/heteroarylchromeno­[4,3-d]­pyrido­[1,2-a]­pyrimidin-6­(7H)-ones (4) was developed based on a three-component tandem reaction between 4-hydroxycoumarin (1), substituted aromatic aldehydes (2), and 2-aminopyridines (3) in the presence of sulfamic acid as a low-cost and ecofriendly solid acid-catalyst in aqueous ethanol at ambient conditions. Expedient metal-free synthesis, good to excellent yields, energy efficiency, use of aqueous ethanol as reaction medium, easy isolation of products, no need of column chromatographic purification, high atom-economy and low E-factor, high turnover number, ecofriendliness, and operational simplicity are some of the salient features of this newly developed protocol.

A simple, straightforward, and convenient one‐pot synthesis of a new series of diversely substituted 1,8‐dioxodecahydroacridines (5a–q and 5′a–g), particularly bearing varying amino acids as part of the building block, has been developed based on a low‐cost and environmentally benign Bi(NO3)3.5H2O catalyst via pseudo‐four component reactions of 1,3‐cyclohexanediones (1/4), various primary amines (2) and aldehydes (3) in ethanol at ambient temperature (25‐30 oC). High atom‐economy, good to excellent yields, eco‐friendliness, and mild reaction conditions are some of the important features of this protocol.

A simple, straightforward, and eco-friendly protocol for one-pot synthesis of a new series of diversely functionalized spiro [indoline-3,5'-pyrido[2,3-d]pyrimidines](4)/spiro[acenaphthylene-1,5'-pyrido[2,3-d]-pyrimidines] (5/5') has been developed based on a three-component reaction between isatins (1)/ acenaphthylene-1,2-dione (1'), malononitrile (2)/2-(phenylsul-fonyl)acetonitrile (2') and 6-aminouracils (3)/6-aminothiouracil (3') in aqueous ethanol under reflux using sodium formate as cheap and non-toxic organocatalyst. Metal-free synthesis, onepot MCR strategy, good to excellent yields, high atom-economy and eco-friendliness are the key advantages of this protocol.

Development of an ultrasound-promoted green protocol to access pharmaceutically relevant functionalized coumarin-uracil molecular hybrids, 6-amino-5-((4-hydroxy-2-oxo-2H-chromen-3-yl)(aryl)methyl)pyrimidine-2,4(1H,3H)-diones (4/ 4′), has been accomplished based on a three-component tandem reaction between 4-hydroxycoumarin (1), substituted aromatic aldehydes (2), and 6-aminouracils (3)/6-amino-2-thiouracil (3′) under sulfamic acid-catalysis in aqueous ethanol. Metal-free onepot synthesis, rapid reaction-rate with good to excellent yields, use of cost-effective and eco-friendly catalyst and solvent, energy efficiency, easy isolation of products without the need of column chromatographic purification, reusability of reaction media, largescale synthetic applicability, and excellent green credential parameters of the process are the salient features of this newly developed method.

A simple, straightforward, and highly efficient three-component one-pot synthesis of a new series of biologically-interesting diverse and functionalized 5-((1H-indol-3-yl)(aryl)methyl)-6-aminopyrimidine-2,4(1H,3H)-dione derivatives has been elaborated based on molecular hybridization approach. The target molecules have been rationalized via tandem reaction of 6-aminouracils, substituted aromatic aldehydes and indoles in the presence of sulfamic acid as a low-cost and eco-friendly organocatalyst in water at room temperature. High atomeconomy, energy-efficiency, use of water as reaction medium, good to excellent yields, metal-free synthesis, eco-friendliness, and operational simplicity are some of the important features of this newly developed protocol.[a] Prof.

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Potassium alum (KAl(SO4)2.12H2O), commonly known as ‘alum’, has recently drawn the attention of synthetic chemists as an efficient, safe and eco-friendly acid catalyst in implementing a large number of organic transformations, thereby generating interesting molecular frameworks. The present review article offers an overview of the potent catalytic applications of this commercially available and low-cost inorganic sulfate salt in organic reactions reported during the period of 2014 to 2018.