Two‐Step Ring‐Transformation Strategy Toward Allomaltol Containing Pyrazolo[1,5‐ a ][1,3,5]Triazine‐2,4‐Diones From Pyrano[2,3‐ f ]Pyrazolo[3,4‐ d ][1,3]Oxazepines via Urea Intermediates

A novel two‐step approach to previously unexplored allomaltol‐containing pyrazolo[1,5‐ a ][1,3,5]triazine‐2,4‐diones has been developed. The method involves the use of fused 1,3‐oxazepin‐2‐one derivatives as precursors, which undergo CO bond cleavage of the carbamate fragment upon treatment with amines, leading to the formation of substituted ureas. Subsequent condensation of these intermediates with 1,1′‐carbonyldiimidazole provides access to the target bicyclic systems. This methodology employs readily available starting materials and proceeds under mild conditions, offering a straightforward protocol with simple product isolation that does not require chromatographic purification. The generality of this approach was demonstrated by the synthesis of 13 urea intermediates and 11 target heterocycles in yields of up to 78%. The structure of one representative product was confirmed by X‐ray analysis.