(R)-3-(N-Cyclobutyl-N-isopropylamino)-8-fluoro-5-trifluoromethylsulfonyloxy-3,4-dihydro-2H-1-benzopyran (1.65 g, 4.01 mmol) was dissolved in a solution of DMF/methanol (6:2, 30 mL) and then degassed followed by the inlet of carbonmonoxide (×3). With a slight positive pressure of carbonmonoxide, palladium(II)-acetate (30 mg), 1,3-bis(diphenylphosphino)propane (55 mg) and triethylamine (1.25 mL, 8.8 mmol) were added and the reaction mixture was degassed and subjected to carbonmonoxide once again. The reaction was heated to 70° C. under carbonmonoxide atmosphere with vigorous stirring for 6 h. The reaction was allowed to cool and the solvent was ether. The combined ether portions were dried (MgSO4), removed in vacuo. The remains were taken into a 2M solution of NH3 and then extracted, twice, with diethyl filtered, and the solvent removed in vacuo to give the crude residue. Chromatography on silica (eluent: 8% ethyl acetate/hexane) gave 1.18 mg (92% yield) of the title compound as a clear oil. [α]21D =-139.1° (C=0.1; CHCl3) GC-MS (70 eV) M=321 (3%).
