Azodicarboxylic acid N-phenylimide reacts with 1-acetyl-3-(2-ferrocenylethe
nyl)-5-ferrocenyl-2-pyrazoline according to the [4+2]-cycloaddition mechani
sm to form a Diels-Alder adduct. Under analogous conditions, 1-acetyl-5-fer
rocenyl-3-(1-cyciohexenyl)-substituted 2-pyrazolines containing allylic hyd
rogen atoms give monoene addition products.