A Benzannulation Strategy for Rapid Access to Quinazoline-2,4-diones via Oxidative N-Heterocyclic Carbene Catalysis

N-Heterocyclic carbene-catalyzed formal [4+2] benzannulation of enals with suitably substituted pyrimidine-2,4-diones allowing the mild and facile synthesis of functionalized quinazoline-2,4-diones is presented. This oxidative transformationproceeds via the simultaneous generation of dienolates and alpha,beta-unsaturated acylazoliums and follows a vinylogous Michael/aldol/beta-lactonization/decarboxylation/oxidation sequence to afford quinazoline-2,4-diones, including axially chiral ones with suitablesubstitutions, in an operationally simple procedure. In addition, substituted coumarins as dienolate precursors affordedbenzochromen-6-one derivatives.

Automated summary

N-Heterocyclic carbene-catalyzed reaction of enals with pyrimidine-2,4-diones allows the mild and facile synthesis of functionalized quinazoline-2,4-diones. The reaction proceeds via the generation of dienolates and acylazoliums, followed by a vinylogousMichael/aldol/beta-lactonization/decarboxylation/oxidation sequence to afford the desired products.