Synthesis of novel annulated uracils via domino Knoevenagel-hetero-Diels-Alder reaction in aqueous media

An efficient synthesis of tetracyclic uracil derivatives (polycyclic pyrans) is achieved via domino Knoevenagel-hetero-Diels-Alder reactions of O-propargylated salicylaldehyde derivatives with 1.3-dimethylbarbituric acid in water as solvent in the presence of Cul. The products are formed in good yields. (C) 2008 Elsevier Ltd. All rights reserved.