Tandem reactions leading to bicyclic pyrimidine nucleosides and benzopyran-4-ones.

A novel, rapid, and efficient synthesis of bicyclic pyrimidine nucleosides and benzopyran-4-ones through oxidation of homopropargyl alcohols and subsequent isomerization, intramolecular addition of enol to allenic ketone has been developed. This methodology provides an efficient and promising approach to the structurally and pharmaceutically interesting pyrano[2,3-d]pyrimidine-2,5-dione nucleoside and benzopyran-4-one derivatives.