Stereospecific formation of polycyclic ferrocenyldihydropyrazoles based on Z- and Å-isomeric ferrocenyl-substituted α,β-unsaturated ketones of the heterocyclic series

The reactions of E- and Z-isomeric 2-(ferrocenylmethylidene)quinuclidin-3-one, 1-methyl-3-(ferrocenylmethylidene)piperidin-4-one, and 2-(ferrocenylmethylidene)tropinone with hydrazine proceed stereospecifically to form the same diastereomeric polycyclic ferrocenyldihydropyrazoles regardless of the geometrical configuration of the starting α,β-unsaturated ketones. The structure of the trans-diastereomer of 4-acetyl-3-ferrocenyl-1,4,5-triazatricyclo[5.2.2.02,6]undec-5-ene was established by X-ray diffraction analysis.