A Facile Three-Component Catalyst-Free Strategy: Synthesis of Indeno[1,2-b][1,6]naphthyridine-1,10(2H)-dione Derivatives in Water

A catalyst-free protocol for synthesizing a new series of indeno[1,2-b][1,6]naphthyridine-1,10(2H)-dione derivatives with good to excellent yields was established based on microwave-assisted domino reaction of 4-aminopyridin-2(1H)-ones, aldehydes and 1H-indene-1,3(2H)-dione in water. The present approach exhibited useful and green features, such as water as reaction solvent, catalyst- and additive- free, short reaction time (20-30 min), as well as ease of desired products separation and purification without the need for column chromatography. Also to note, up to four new bonds were formed accompanied by generating water as sole by-product in this one-pot procedure.