“…A mixture of perfluoroalkyl azide 1b (3 mmol, 1.47 g) and phenylisocyanate 2b (3 mmol, 0.36 g) was reacted and the product purified in the same manner as for 3c to obtain tetrazol-5-one 3d as a -oxo-4-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluororoctyl)-4,5-dihydro-1H-tetrazole-1-sulfonate (3e) A mixture of perfluoroalkyl azide 1a (3 mmol, 1.17 g) and 2,4,6-trimethylphenylsulfoxy isocyanate 2c (3 mmol, 0.72 g) was reacted and the product purified in the same manner as for 3c to obtain tetrazol-5-one 3e as a viscous oil; IR: n 1722 cm À1 (C O) 3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)-5-oxo-4,5-dihydro-1H-tetrazole-1-sulfonate (3f)…”