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A one‐pot, three‐component, and atom economic synthesis of biologically and pharmaceutically important fully substituted and functionalized pyrazole derivatives has been accomplished under metal‐catalyst‐free benign conditions. The strategy involves early condensation of readily available cyclic β‐diketones (dimidone, 4‐hydroxycoumarin and 2‐hydroxy‐1,4‐naphthoquinone) and arylglyoxals to generate a chalcone type intermediate which upon acid catalyzed condensation with ambident nucleophile arylhydrazones produces various aryl and cyclic β‐diketone substituted pyrazole derivatives. The synthesis embraces high functional group tolerance, broad substrate scope, excellent yield of the products, short reaction time and operationally simple and mild reaction conditions. The synthesis provides an easy opportunity of incorporating biologically important N‐diarylsulfide/selenide functionality, various enolisable cyclic β‐diketones and other bioactive heterocycles concurrently to pyrazole, which may help in designing and development of pyrazole derivatives of pharmacological significance. [ABSTRACT FROM AUTHOR]

A magnetically separable core–shell CoFe2O4@SiO2‐SO3H nanocatalyst has been successfully exploited as a heterogeneous acid catalyst in the synthesis of diversely substituted biologically important spiro fused pyrrolo/indolo[1,2‐a]quinoxaline derivatives through the condensation of N‐(2‐aminophenyl)pyrroles/indoles and various cyclic conjugated 1,2‐diones in ethanol under ultrasonic irradiation. Room temperature synthesis, short reaction time, wide substrate scope, good to excellent yield of products and use of a magnetically separable and recyclable nanocatalyst make this method attractive and practicable. A magnetically separable CoFe2O4@SiO2‐SO3H nanocatalyst having core–shell morphology has been employed for the very first time in a benign strategy to synthesize a series of novel spiro fused quinoxaline derivatives under ultrasonic irradiation. Spiro fused quinoxaline derivatives derived from acenaphthoquinone, 9,10‐phenanthroquinone and [1,2]benzoquinone are reported. Room temperature synthesis, shorter reaction time, wide substrate scope, good to excellent yield and use of a magnetically separable and recyclable nanocatalyst make this synthetic protocol attractive. [ABSTRACT FROM AUTHOR]