Organoiron complexes in organic synthesis. Part 24. Studies in the synthesis and reactivity of 6-exo-substituted cyclohexadienylium(tricarbonyl)iron salts

Abstract

Tricarbonyliron derivatives of 5-substituted cyclohexa-1,3-dienes bearing a β-hydroxy-group in the substituent undergo thallium(III)-promoted oxidative cyclisation to give tetrahydrobenzofuran(tricarbonyl)iron complexes. The metal can be removed to give the corresponding tetrahydrobenzofuran derivatives, or the complexes may be treated with tetrafluoroboric acid in acetic anhydride to give 6-exo-substituted cyciohexadienylium(tricarbonyl)iron complexes. Reactions of these cationic derivatives with nucleophiles is reported.