One-pot syntheses of 2-pyrazoline derivatives

Hydrazinediium dithiocyanate and α,β-unsaturated ketones give in one-pot reactions 1-thiocarbamoyl-2-pyrazolines and 1-formyl-2-pyrazolines. The syntheses of pyridine-2-thiones, pyrimidine-2-thiones and bicyclo[2.2.2]octan-2-ones from ammonium thiocyanates and ketones by analogous procedures are reviewed. The mechanisms of the ring formations are discussed. Crystal structure analyses of a 1-thiocarbamoyl- and a 1-formyl-2-pyrazoline are given.