Selective O- and N-nitration of steroids fused to the pyrazole ring

Chemoselective methods for O- and N-nitration of steroids fused to the pyrazole ring were developed. The nitrating agents were acetyl, propionyl, and trifluoroacetyl nitrates generated from carboxylic acid anhydrides and either copper nitrate or nitric acid. Depending on the reaction conditions, the developed methods allow both selective nitration at the pyrazole nitrogen atom leaving intact the hydroxy group of steroid framework and dinitration giving rise to the corresponding nitrates of steroidal nitropyrazoles.