Cascade Reaction of 1,1-Enediamines with 2‑Benzylidene‑1<i>H</i>‑indene-1,3(2<i>H</i>)‑diones: Selective Synthesis of Indenodihydropyridine and Indenopyridine Compounds

A concise and environmentally friendly route for the synthesis of diverse indenodihydropyridines (<b>3</b>) via a cascade reaction of 1,1-eneamines (<b>1</b>) with benzylidene-1<i>H</i>-indene-1,3­(2<i>H</i>)-diones (BIDs) (<b>2</b>) in ethanol media was developed. The targeted compounds were efficiently obtained by only filtration without any further post-treatment. In the one-step cascade reaction, C–C and C–N bonds were constructed. In addition, when 1,4-dioxane was used as a solvent and the mixture of 1,1-eneamines (<b>1</b>) was refluxed with benzylidene-1<i>H</i>-indene-1,3­(2<i>H</i>)-diones (BIDs) (<b>2</b>) for about 12 h, indenopyridine compounds (<b>4</b>) were produced. Two kinds of indenopyridine derivatives <b>3</b>–<b>4</b> resulted from alternative solvents and temperatures. The reaction had the following features: mild temperature, atom economy, high yields, and potential biological activity of the product.