2-Pyrazolin-4-oximes have been synthesized by reaction of 4-nitroso-and 4-nitropyrazoles with complex metal hydrides and organometallic reagents. Furthermore, 4-nitropyrazolium tetrafluoroborates are reactive substrates towards organolithium and Grignard compounds leading to new and highly substituted 4-nitro-3-pyrazolines and 4-nitropyrazolidines. The formation of 3-pyrazolines is regioselective and, when diastereoisomer pyrazolidines are ...