Polycyclic ferrocenyl-4,5-dihydropyrazoles in nucleophilic reactions with β-dicarbonyl compounds

Polycyclic ferrocenyldihydropyrazoles with a free NH group react with ethyl acetoacetate and acetylacetone to give the corresponding enamino carbonyl compounds isolated as E-isomers. The spatial structure of (E)-4-[1-(ethoxycarbonyl)prop-2-en-2-yl]-3-ferrocenyl-1,4,5-triazatricyclo[5.2.2.02,6]undec-5-ene was determined using X-ray diffraction analysis. Spontaneous isomerization of (E)-(4-oxopent-2-en-2-yl)(ferrocenyl)dihydropyrazoles into the respective Z-isomers was observed.