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The one‐pot three‐component domino reaction of 2‐acetylphenothiazine, 4‐Cl/4‐Me benzaldehyde and malononitrile afforded 3‐amino‐4′‐chloro/4′‐methyl‐5‐(10H‐phenothiazin‐2‐yl)‐[1,1′‐biphenyl]‐2,4‐dicarbonitriles in good yields. These phenothiazine‐tethered biaryls exhibited strong red fluorescence under UV lamp in solid state and green fluorescence in DMSO. These probes were sensitive towards multi‐analytes like Fe3+, Cu2+, picric acid and 4‐nitrophenol with good lower limit of detection.

3‐Amino‐5‐(thiazol‐2‐yl)‐[1,1′‐biaryl]‐2,4‐dicarbonitriles have been synthesized employing a facile one‐pot pseudo four‐component domino strategy. All these thiazole‐tethered biaryls exhibited blue fluorescence under UV lamp. Based on the high relative quantum yield, three compounds namely, 4a, 4d, and 4i, were chosen to explore the metal interference studies. Against several metal ions, these three thiazole‐tethered biphenyl probes were found to be effective fluorescent chemosensors for the selective and sensitive detection of Fe3+ ions with a lower detection limit of 0.18, 0.12, and 0.16 μM, respectively.

The synthesis of novel isoxazolo [5,4-b]pyrano[2,3-f]quinoline hybrids has been achieved through a one-pot three-component reaction of 3-methyl-7,8-dihydroisoxazolo [5,4-b]quinolin-5(6H)-one, isatins or aromatic aldehydes and malononitrile in the presence of a base at ambient temperature. The reaction occurred through a domino Knoevenagel-Michael type addi-tion-O-cyclization sequence in a single transformation to afford the products in excellent yields. One of the isoxazolo [5,4b]pyrano [2,3-f]quinoline was found to be highly sensitive towards picric acid with a lower limit of detection of 1.2 μM and quenching constant of 2.

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