Nitrotetrazolo pyridines, ring

Nitrotetrazolo[l,5-/]furazano[4,5- ]pyridine 1-oxide 340 (NFP) was prepared by the extrusion of nitrogen from 2,6-diazido-3,5-dinitropyridine followed by ring closure (Scheme 85) <2005JEM99>. 

Although the ring transformation of 8-nitrotetrazolo[l,5-a]pyridine (41) to oxadiazolo[3,4-h]py-ridine-1-oxide (42) has been known for a long time <53JA5298>, the reinvestigation of this conversion <80M407,90JOC3755) led to elaboration of a safe laboratory procedure for the synthesis of this fairly unstable product (42) (Equation (10)). 

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