A mixture of 2.0 g (4.17 mmol) of the compound from Example 1A, 1.95 g (6.26 mmol) of the compound from Example 8A, 256 mg (0.280 mmol) of tris(dibenzylideneacetone)dipalladium(0), 398 mg (0.835 mmol) of 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (X-Phos) and 2.72 g (8.35 mmol) of caesium carbonate in 20 ml of anhydrous DMF was heated to 120° C. under argon in a microwave oven (Biotage Initiator, dynamic control of the incident power) for 2.5 h. After cooling to RT, 100 ml of water were added to the reaction mixture, which was extracted three times with approx. 100 ml each time of ethyl acetate. The combined organic extracts were washed successively with water and saturated sodium chloride solution, dried over anhydrous magnesium sulphate, filtered and finally freed of the solvent on a rotary evaporator. The remaining residue was dissolved in 40 ml of THF, and 6.3 ml (6.26 mmol) of a 1 M solution of tetra-n-butylammonium fluoride (TBAF) in THF were added. After this mixture had been stirred at RT for 1 h, it was subjected to aqueous workup in the same way as described above. The remaining residue was purified by suction filtration through 200 g of silica gel with 2:1 (3 liters)→1:1 (3 liters) cyclohexane/ethyl acetate as the eluent. After concentration and drying under a high vacuum, 1.56 g (79% of theory) of the title compound were obtained.
