Formation of pyridazino[4,5-c]pyridazine derivatives upon [4+2]cycloaddition of 4-phenyl-1,2,4-triazoline-3,5-dione to cross-conjugated monoferrocenyltrienes

摘要

Cross-conjugated monoferrocenyltrienes react with 4-phenyl-1,2,4-triazoline-3,5-dione to give monoand bis-[4+2]-cycloaddition products. Nonsubstituted and 2,4-disubstituted 3-feffocenylmethylidenepenta-1,4-dienes afford respective pyridazine and pyridazino[4,5-c]pyridazine derivatives. Their structures were established based on H-1 and C-13 NMR data and X-ray diffraction analysis.