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An efficient green protocol has been investigated for the synthesis of pyrimido[4,5-b]quinolines derivatives via one-pot three-component condensation of 4-chloro aniline, aromatic aldehyde and barbituric acid using low transition temperature mixtures as new generation and sustainable solvents. The process was accomplished with the use of greener and recyclable reaction media, simple methodology, easy workup procedures and no chromatographic purification with high yield. This new approach is expected to discover some significance in combinatorial synthesis of biologically active scaffolds. Graphical Abstract: [ABSTRACT FROM AUTHOR]

A series of novel 7-(3-chloro-phenyl)-10-thioxo-7,9,10,11-tetrahedro-6 H-pyrimido-[5′4′:5,6] pyrano[3,2-c]quinoline-6,8(5 H)-dione derivatives have been synthesized through the multi-component condensation of aromatic aldehydes, barbituric acid, and 2,4-dihydroxy quinoline, using heterogeneous sulfamic acid catalyst in water-ethanol (4:1) solvent system under reflux condition. The present protocol is endowed with charming description such as green synthetic procedure, short reaction time, easy work-up procedure, and excellent yield and high atom economy of pyranoquinoline derivatives. In this study, sulfamic acid is used as a heterogeneous catalyst that is easily recoverable and recyclable. The proposed multi-component reaction has been studied with detail mechanism and spectroscopic data. This is one of the potential greener synthetic approaches to build up the series of pyranoquinoline heterocycles. [ABSTRACT FROM AUTHOR]

A series of novel 7-phenyl-7,12-dihydrobenzo( h)pyrido[2,3- b]naphthydrin-6(5 H)-one were synthesized by a one-pot three-component condensation of 2,4-dihydroxyquinoline, 2-amino pyridine and various aromatic aldehydes with sulfamic acid as an enviro-economic catalyst. The salient features of this method consist of high atom economy and yields, short reaction time, non-carcinogenic solvents, and chromatography-free work-up procedure. Fascinatingly, the catalyst can be reused for up to four cycles giving good to excellent yields. By employing this method, a series of 14 pyrido[2,3- b]naphthydrin compounds were synthesized. This procedure is projected as a green avenue in the combinatorial synthesis of biologically active naphthydrin derivatives. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Polystyrene-supported sulfonic acid has been found to be an efficient catalyst for the one-pot, three-component synthesis of 2 H-indazolo[2,1- b]phthalazinetriones in greener solvent glycerol. Use of greener solvent glycerol along with a polymer-supported, low toxic, and inexpensive catalyst renders the method eco-friendly. High yields, simple product isolation procedure, and fluorescent and electroluminescent natures of the products are the noteworthy aspects of this protocol. [ABSTRACT FROM AUTHOR]

Abstract: Relatively less toxic and biodegradable ionic liquid [C8dabco]Br has been successfully used for the synthesis of quinoxaline and phthalazinetrione derivatives in an aqueous media. Recyclability of catalyst, high yields, use of environmentally benign aqueous media as solvent, simple product isolation and high atom economy are the noteworthy aspects of the protocols. [Copyright &y& Elsevier]