Synthesis of unsymmetrical dihydro triazine-2,4-diones by the N–N bond fragmentation of urazoles followed by intramolecular cyclization

[Display omitted] A new synthesis of unsymmetrical dihydro triazine-2,4- diones has been accomplished, through the strategy of a base-induced fragmentation of urazole derivatives, followed by an intramolecular cyclisation. Treating substituted urazole derivatives with LDA resulted in fragmentation of the N–N bond generating an imine, which was trapped in an intramolecular fashion to give products in good to excellent yields. Features of this transformation include atom economy and a broad tolerance of aryl substituents. Where differentially substituted urazole derivatives are employed, only one dihydro triazine-2,4-dione isomer is obtained. We also demonstrate the transformation of such dihydro triazine-2,4-diones into triazine-2,4-diones and triazine-2,4,6-triones, enlarging the scope of this approach.