8.5 ml (21 mmol) of a 2.5M solution of butyllithium in hexane were added dropwise to 1.4 g (21 mmol) of cyclopentadiene in 45 ml of O2 -free and H2O-free THF at 0° C. under argon and the mixture was stirred for a further 2 hours at room temperature. This solution was subsequently added at room temperature to a solution of 7.9 g (21 mmol) of 2 in 100 ml of O2 -free and H2O-free THF over a period of 2 hours and the mixture was stirred for a further 1 hour at room temperature. 50 ml of H2O were added, the phases were separated and the aqueous phase was further extracted twice with 30 ml of Et2O each time. The combined organic phases were dried (MgSO4) and the solvent was removed in vacuo. After chromatography on 200 g of silica gel (hexane/methylene chloride 20:1), 4.4 g (51%) of 3 were obtained as a colorless oil.
