A straightforward, environmentally beneficial synthesis of spiro[diindeno[1,2-b:2′,1′-e]pyridine-11,3′-indoline]-2′,10,12-triones mediated by a nano-ordered reusable catalyst

A library of new spiro[diindeno[1,2-b:2′,1′-e]pyridine-11,3′-indoline]-2′,10,12-trione derivatives has been prepared in an efficient, one-pot pseudo four-component method mediated by a reusable heterogeneous nano-ordered mesoporous SO(3)H functionalized-silica (MCM-41-SO(3)H) catalyst. Excellent yields, short reaction times, as well as convenient non-chromatographic purification of the products and environmental benefits such as green and metal-free conditions constitute the main advantages of the developed synthetic methodology. The obtained fused indole-indenone dyes would be of interest to pharmaceutical and medicinal chemistry. Furthermore, due to their sensitivity to pH changes, they could be used as novel pH indicators.