Coumarin (benzopyran-2-one) derivatives are widespread in nature. This oxyheterocyclic scaffold is present in several pharmacologically active molecules, both synthetic and natural. Although the chemistry and biology of coumarin derivatives have been broadly explored but the synthesis of 4-aminocoumarin bearing chromeno[4,3-b]quinolin-6-ones has not been extensively investigated, in particular, when sustainability is related to the synthesis. As a part of our ongoing research related to green methodology development, a microwave-assisted ‘on water’ protocol to synthesize 4-aminocoumarin bearing chromeno[4,3-b]quinolin-6-ones has recently been developed. Initially, 4-aminocoumarin was synthesized from 4-hydroxycoumarin reacting with ammonium acetate under microwave irradiation (neat). In the subsequent step, ‘on water’ reaction of 4-aminocoumarin with o-fluorobenzaldehyde under controlled microwave exposure produced the target molecule with the elimination of hydrogen fluoride. No hazardous solvent/catalyst/solid support was used to accomplish the reaction. Clean reaction technique, shorter reaction period, easy work-up procedure, high yield of the product, and retention of atom-economy are important aspects of this green synthetic method.

Expedient ‘on water’ chemoselective green synthesis of 4-aminocoumarin bearing chromeno[4,3-b]quinolin-6-ones

255th National Meeting (2018)

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