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

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Abstract
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,3and17, were preparedviathe 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.