Microwave assisted highly efficient one-pot multi-component synthesis of novel 2-(tetrasubstituted-1H-pyrrol-3-yl)-4H-chroman-4-ones catalyzed by heterogeneous reusable silica gel supported polyphosphoric acid (PPA/SiO 2 )

Aza‐Michael Mono‐ and Bis‐Addition of Primary and Secondary Amines Promoted by Silica‐Supported Polyphosphoric Acid, PPA/SiO2

“…In addition, the catalyst can be easily separated from the reaction mixtures by simple filtration and is reusable. [26][27][28] Because of its ability to promote bis-aza-Michael addition the PPA/SiO 2 catalyst was chosen for further investigation. Efforts to make the selected catalyst entirely mono-selective proved to be futile.…”

Solvent‐Free Synthesis of Pyrroles: An Overview

“…An environmentally benign strategy for the synthesis of pyrroles was introduced in 2015 via one-pot, solvent-free, reaction of aldehyde, amine, nitroalkane and 1,3-dicarbonyl compounds. [45] The silica gel supported polyphosphoric acid (PPA/SiO 2 ) catalyst was used under microwave-irradiation. The optimised condition includes the use of 10 mg of PPA-SiO 2 at 90 °C under neat reaction condition.…”

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

“…The diverse pharmacological activities of pyrroles enlivened Kumar and co-workers [61] to report a facile and eco-friendly microwave-assisted four-component reaction involving chromene-aldehyde (61), amines 32, acyclic 1,3-diketones 54 and nitromethane using silica-gel-supported polyphoshoric acid as catalyst under neat conditions for the synthesis of tetrasubstituted pyrroles 62. A comparative study of the protocol employing the conventional and microwave approach proved the microwave strategy to be advantageous with enhanced yield from 87-95% in reduced time (3 h to 46 min).…”