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112. Ring Closure Reactions of 5-Azidopyrido[2,3-d]pyrimidinetriones to Isoxazolo- and Oxadiazolopyrido[2,3-d]pyrimidinetriones
Dang V. T. and W. Stadlbauer, J. Heterocyclic Chem. 45, (2008) 1695-1699 .

Thermal decomposition of 5-azidopyrido[2,3-d]pyrimidines 2 and 7 having reactive ortho-substituents such as a formyl or a nitro group yielded isoxazolo[3',4':4,5]pyrido[2,3-d]pyrimidines 3 or oxadiazolo[3',4':4,5]pyrido[2,3-d]pyrimidines 9. The reaction conditions of the azide decomposition was studied by differential scanning calorimetry (DSC). Desoxygenation of N-oxides 9 to oxadiazoles 10 and regioselective reduction of azides 7 to amines 8 were studied in addition.

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