Reaktion von 3‐Dimethylamino‐2,2‐dimethyl‐2 H ‐azirin mit Barbitursäure

Reaction of 3‐Dimethylamino‐2,2‐dimethyl‐2 H ‐azirine with Barbituric Acid The reaction of 3‐dimethylamino‐2,2‐dimethyl‐2 H ‐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 NaBH 4 in ethanol at room temperature yields 6,6‐dimethyl‐1,5,6,7‐tetrahydro‐pyrrolo[2,3‐ d ]pyrimidin‐2,4(3 H )‐dione (7) and 3,3‐dimethyl‐2,3‐dihydro‐imidazo[1,2‐ c ]pyrimidin‐5,7(1 H , 6 H )‐dione (8) in 38 and 48% yield, respectively. Treatment of 6 with 3 N aqueous NaOH at room temperature gives 3,3‐dimethyl‐imidazo[1,2‐ c ]pyrimidin‐2,5,7 (1 H , 3 H , 6 H )‐trione (9) in 51% yield ( Scheme 3 ).