Acetonylation of 5(3)-(1H-tetrazol-1-yl)-3(5)-nitro-1H-pyrazole

N-Acetonylation of 5(3)-(1H-tetrazol-1-yl)-3(5)-nitro-1H-pyrazole with bromoacetone in the presence of NaHCO₃ at 60°C gave, along with expected isomeric N-acetonyl derivatives, a tricyclic product of the intramolecular electrophilic attack at the carbon atom of the tetrazole cycle.