Reaction of 3-Dimethylamino-2,2-dimethyl-2H-azirine with Barbituric Acid.
The reaction of 3-dimethylamino-2,2-dimethyl-2H-azirine (1) with barbituric acid (4) in dimethyl formamide at room temperature yields a mixture of several compounds. The two main products 5 and 6 have been isolated in 40 and 10% yield, respectively, and their structures established by X-ray analysis. In Schemes 4-6 reaction mechanisms for the formation of 5 and 6 are postulated, the first step beeing either a C- or an N-alkylation of barbituric acid.
Reduction of 5 and 6 with NaBH4 in ethanol at room temperature yields 6,6-dimethyl-1,5,6,7-tetrahydro-pyrrolo[2,3-d]pyrimidin-2,4(3H)-dione (7) and 3,3-dimethy1-2,3-dihydro-imidazo[1,2-c]pyrimidin-5,7(1H,6H)-dione (8) in 38 and 48% yield, respectively. Treatment of 6 with 3N aqueous NaOH at room temperature gives 3,3-dimethyl-imidazo[1,2-c]pyrimidin-2,5,7(1H,3H,6H)-trione (9) in 51% yield (Scheme 3).