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

A concise and environmentally friendly route for the synthesis of diverse indenodihydropyridines (3) via a cascade reaction of 1,1-eneamines (1) with benzylidene-1H-indene-1,3­(2H)-diones (BIDs) (2) 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 (1) was refluxed with benzylidene-1H-indene-1,3­(2H)-diones (BIDs) (2) for about 12 h, indenopyridine compounds (4) were produced. Two kinds of indenopyridine derivatives 3–4 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.