Different Rearrangement Behaviour of the Cation or Anion Derived from the Diels–Alder Adduct of 9‐Ferrocenylanthracene and 1,4‐Benzoquinone: Ring‐Opening or Paddlewheel Formation

AbstractPrototropic rearrangement of the Diels–Alder adduct (3 a) of 9‐ferrocenylanthracene and 1,4‐benzoquinone potentially furnishes 9‐ferrocenyl‐1,4‐dihydroxytriptycene (3 b) incorporating aC2vsymmetrical paddlewheel moiety. However, reaction of3 awith HBF4unexpectedly yields instead 9‐ferrocenyl‐10‐(2,5‐dihydroxyphenyl)anthracene (4) via cleavage of the C9C12 bond to generate initially a ferrocenyl‐stabilized cation. Treatment of3 awith sodium hydride and iodomethane yields 1,4‐dimethoxy‐9‐ferrocenyltriptycene (3 c) in high yield but, surprisingly, also leads to fission of the C9C12 bond resulting, after methylation, in the formation of 9‐hydroxy‐9‐ferrocenyl‐10‐(2‐hydroxy‐5‐methoxyphenyl)dihydroanthracene (12), which readily dehydrates on silica to form 9‐ferrocenyl‐10‐(2‐hydroxy‐5‐methoxyphenyl)anthracene (8). The X‐ray crystal structures of3 a,3 cand4are reported.

Different Rearrangement Behaviour of the Cation or Anion Derived from the Diels–Alder Adduct of 9‐Ferrocenylanthracene and 1,4‐Benzoquinone: Ring‐Opening or Paddlewheel Formation Journal Articles