An Expedient and Divergent Tandem One-Pot Synthesis of Pyrimidin-2,4-diones Using the Blaise Reaction Intermediate

A novel divergent tandem one-pot method for the synthesis of 3,5,6-trisubstituted 1H-pyrimidin-2,4-dione derivatives is developed. In the presence of 10 mol % of Cu(OAc)₂, the α-substituted Blaise reaction intermediates (R² ≠ H) reacted with isocyanates chemoselectively to afford pyrimidin-2,4-diones, whereas the α-unsubstituted Blaise reaction intermediate (R² = H) showed a propensity to be a C-nucleophile toward electrophiles, permitting the installation of different functionalities at the 5-position through sequential tandem reactions.