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-1 H -indene-1,3(2 H )-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-1 H -indene-1,3(2 H )-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.