Reactivity of co-ordinated ligands. Part XXIII. Preparation of some cyclic ketones using tricarbonyliron complexes in the presence of aluminium trichloride

Abstract

The reaction of tricarbonyl(η-cyclo-octatetraene)iron with anyhdrous aluminium trichloride in benzene gives tricarbonyl(2–4-η,8-σ-9-oxobicyclo[3.2.2]nona-2,6-dien-8-yl)iron which has been previously obtained from the direct reaction of barbaralone with enneacarbonyldi-iron. Treatment of this complex with carbon monoxide under moderate pressures and temperatures (100 atm, 120 °C) yields barbaralone in 95% yield. Extension of this reaction to other co-ordinated diene systems, e.g. Tricarbonyl(η-cyclo-octatriene)-, tricarbonyl(1-σ,4–6-η-cyclo-octenediyl)-, and tricarbonyl(η-norbornadiene)-iron, provides a convenient method of production of other cyclic ketones.