Synthesis of 1,3‐dialkylpyrazolo [1,5‐ a ]‐1,3,5‐triazine‐2,4‐diones isomers of 1,3‐dialkylxanthines

The synthesis of a new series of alkylxanthine analogs containing a bridgehead nitrogen atom is reported. 1,3‐Dialkylpyrazolo[1,5‐ a ]‐1,3,5‐triazine‐2,4‐diones, were prepared by the treatment of 3‐methylpyrazolo[1,5‐ a ]‐1,3,5‐triazine‐2,4‐dione (3) with the corresponding alkyl iodide. Similarly, the reaction of 3‐methyl‐7‐phenylpyrazolo[1,5‐ a ]‐1,3,5‐dialkyl‐7‐phenylpyrazolo[1,5‐ a ]‐1,3,5‐triazine‐2,4‐diones. The starting materials, 3 and 17 , were prepared via the reaction of an appropriate 3‐aminopyrazole with ethoxycarbonyl isothiocyanate. Several 8‐bromo derivatives were prepared by direct bromination of the 1,3‐dialkylpyrazolo[1,5‐ a ]‐1,3,5‐triazine‐2,4‐diones.