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A catalyst-free combinatorial library of novel 2-amino-4-(5-hydroxy-3-methyl-1H-pyrazol-4-yl)-4H-chromene-3-carbonitrile derivatives has been developed by a four-component reaction between hydrazine hydrate (1), ethyl acetoacetate (2), 2-hydroxybenzaldehydes (3) and malononitrile (4) in water at ambient temperature. [ABSTRACT FROM AUTHOR]

From the array of small molecule organic fluorophores available as functional materials and in biology, synthetic procedures that allow for a simpler and rapid synthesis of organic fluorophores with desirable photophysical properties are in high demand. In addition, fluorophores with good brightness and tuneability in both solid and solution states are only available in certain numbers. Herein, we introduce a new family of pyrrolo[2,1- a ]isoindolylidene-malononitrile (PIYM) fluorophores that exhibit pronounced emission in the visible region in solution and red-NIR emission in the solid state, with tuneability, efficient brightness and stability. PIYM fluorophores were efficiently synthesized via two simple MCR reaction pathways from commercially available, as well as newly synthesized, building blocks. Furthermore, the observed photophysical nature is rationalized from both electrochemical and theoretical calculations (DFT and TD-DFT). In the future, we anticipate that these PIYM fluorophores, with their excellent stability and lower molecular weight, will open ways to enhance the development of NIR-emitting fluorophores with more significant applications in both materials and biological fields.

A library of 4 H -chromene derivatives with heterocyclic substituent's at the 3 and 4-positions was synthesized in a convenient DBU catalysed three component synthesis between salicylaldehyde, acetonitrile derivatives and thiazolidinedione to afford 2-amino-3-benzothiazole-4-heterocycle-4 H -chromenes and 2-amino-3-thiophenoyl-4-heterocycle-4 H -chromenes derivatives in ethanol and a mixture of ethanol and water (1 : 1) at room temperature. The significance of this protocol is the feasibility of incorporating substituents simultaneously at the 3 and 4 positions of 4 H -chromenes in an efficient three component reaction., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)