In(OTf)3-catalysed A3-annulation strategy towards the synthesis of pyrazole-tethered quinoline derivatives and assessment of their luminescent properties†

An In(OTf)₃-catalysed approach has been devised for the synthesis of fluorescent pyrazole-tethered quinoline derivatives via the A³-coupling of 4-formyl-pyrazole-3-carboxylates, substituted aromatic amines and terminal alkynes. This strategy offers several advantages, including the use of readily available and inexpensive starting materials, broad substrate scope, sustainable reaction conditions and high product yields. This strategy is amenable to gram-scale synthesis, and the scope of this methodology was demonstrated for the synthesis of a library of 32 novel pyrazole-tethered quinoline derivatives, with yields up to 96%. The photophysical properties of these pyrazole-tethered quinolines were estimated and excellent results were obtained with a quantum yield (Φ_F) of up to 75%.