Highly enantioselective Biginelli reaction using sulfonic-functionalized chiral hyperbranched polylysine in absence of solvent: A new catalyst for asymmetric synthesis of dihydropyrimidinones

In summary, this paper describes synthesis of a new acidic catalyst to accomplish highly enantioselective Biginelli reactions. Sulfonic-functionalized hyperbranched polylysine (HBPL-SO₃H) as a novel and efficient catalyst help synthesize a series of optically active dihydropyrimidinones via asymmetric synthesis. The reactions carried out under solvent-free conditions at 70 °C within 7 h and produced chiral dihydropyrimidinones in high yields with very good enantiomeric excess. This catalyst could be used at least 5 times without considerable decrease in activity and also induction of chirality. Simple work-up, high yield and enantiomeric excess are some of important advantages of performed reactions with this catalyst. The related organocatalyst was synthesized with 98% yield and its structure was confirmed by IR, NMR, XRD, TGA analysis.