A simple and convenient protocol for the tandem synthesis of 1,5‐diketone via chalcone intermediate from aldehyde and acetophenone using biodegradable choline hydroxide (ChOH), a Room Temperature Ionic Liquid (RTIL) and effect of hydrogen bonding is described. The mechanistic investigation for unusual reactivity of 10‐propyl‐10H‐phenothiazine‐3‐carbaldehyde with o‐hydroxy acetophenone showed involvement of the H‐bonding. Shorter reaction time, easy work up and comparably good yield of desired product are crucial features of this methodology which make it an alternative to the other approaches. The ionic liquid used here serves both as catalyst as well as solvent.

A simple and convenient method for the tandem synthesis of 4, 4-(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ol)s via 3-methyl-1-phenyl-5-pyrazolone from aldehyde, phenyl hydrazine and ethyl acetoacetate using combination of Deep Eutectic Solvent (DES) and ultrasound in water is described. Shorter reaction time, easy work up and comparably good yield of desired product are crucial features. One pot Knorr synthesis and Knovenagel-Michael reaction and use of water as solvent make this methodology an alternative to the other approaches. The advantage of applying ultrasound is, it reduces required time and temperature for reaction with improved yield. The DES and water used here recycled five times without considerable loss of activity.

Synthesis of a stable diazonium salt at room temperature followed by the synthesis of monoazo pigments using DES–ethanol system.

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One pot multi‐component, simple and energy efficient protocol for the synthesis of 2,4,6‐triaryl pyridines mediated via a unique blend of deep eutectic solvents (DES) and concentrated solar radiations (CSR) has been developed. The choline chloride: malonic acid DES employed herein plays a dual role of catalyst and solvent. The employment of CSR is found to be superior to thermal methods in terms of time and energy conservation. Up to 66% of energy conservation is observed following the developed protocol. The amalgamation of DES and renewable energy (CSR), easy synthesis and workup procedure renders the protocol energy efficient and environmentally benign.