Under argon, 16 g (45.42 mmol) of 5-hydroxy-4-oxo-3,4-dihydrospiro[chromen-2,1′-cyclobutan]-7-yl trifluoromethanesulfonate (Example 44A), 3.71 g (4.54 mmol) of [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) and 5.78 g (136.25 mmol) of lithium chloride are suspended in 400 ml of abs. dimethylformamide. The mixture is cooled to 0° C., 90.8 ml (90.8 mmol) of diisopropylzinc (1 M solution in toluene) are added and the mixture is stirred at this temperature for 4 hours. At 0° C., saturated ammonium chloride solution is then added to the mixture. The mixture is diluted with water, 1 N hydrochloric acid and ethyl acetate, the organic phase is separated off and the aqueous phase is extracted repeatedly with ethyl acetate. The combined organic phases are washed twice with water and once with saturated sodium chloride solution, dried over sodium sulfate, filtered and concentrated. The residue is adsorbed on silica gel and purified on a silica gel column (mobile phase: cyclohexane→cyclohexane/ethyl acetate 20:1). This gives 9.6 g (86% of theory) of the title compound.
