Zur Bildung polycyclischer Ketone bei der Umsetzung von 5, 6‐Dimethyliden‐bicyclo[2.2.1]hept‐2‐en mit Dieisen‐enneacarbonyl

On the Formation of Polycyclic Ketones in the Reaction of 5, 6‐Dimethylidene‐bicyclo[2.2.1]hept‐2‐ene with Diiron‐enneacarbonyl 5,6‐Dimethylidene‐bicyclo[2.2.1]hept‐2‐ene (4), in the presence of diiron‐ennea‐carbonyl in boiling hexane, produces the endo‐and exo‐tricarbonyl‐iron complex of 4 (endo‐ and exo‐5). A mixture of numerous tricarbonyl‐iron complexes with ligands derived from coupling and carbonylation reactions of 4 are also formed. The endo‐ and exo‐5 compounds as well as two tricarbonyl‐iron complexes (7 and 8) of penta‐cyclic ketones could be isolated and characterized. After oxidative removal of the tricarbonyl‐iron groups in the reaction mixture the three pentacyclic ketones 9, 10 and 11 were separated. Structure and configuration of these ketones were deduced from spectroscopic analyses, especially from their 1H‐ and 13C‐NMR. spectra (see tables 1–4). Whereas the symmetric pentacyclic ketone 11 is of a known type (cf. [1]) the two spiroketone 9 and 10 represent compounds of a new type. Their structure and configuration shows that in ironcarbonyl induced thermal cyclopentanone formations, an exocyclic double bond can also take part.