Silica sodium carbonate: the most efficient catalyst for the one-pot synthesis of indeno[1,2-b]quinoline and spiro[chromene-4,3′-indoline]-3-carbonitriles under solvent-free condition

A new silica sodium carbonate-assisted convenient and efficient strategy for the synthesis of indeno[1,2- b ]quinoline and spiro[chromene-4,3′-indoline]-3-carbonitriles derivatives in solvent-free media is described. The reactions can be performed at low catalyst loadings with excellent functional group tolerance. The catalyst can be easily recovered and reused for the next reaction for at least three runs without any significant impact on the yields of the products. The easy recovery of the catalyst and high yield of the products make the protocol attractive, sustainable, and economic. Graphical abstract