To a stirred solution of 4.36 g (15.6 mmol) 2-(4-methoxy-3-nitro-phenyl)-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane (VII) and 3.30 g (14.2 mmol) trifluoromethanesulfonic acid 3,6-dihydro-2H-pyran-4-yl ester in 33 ml ethanol and 82 ml toluene was added 580 mg (0.71 mmol) dichloro(1,1′-bis(diphenylphosphino)ferrocene)palladium(II) dichloromethane adduct. The mixture was heated at 80° C. and 16.5 ml (33.0 mmol) 2 M aqueous sodium carbonate solution was added dropwise. The reaction mixture was stirred for 20 minutes at 80° C. and then cooled to room temperature, poured onto water, and extracted three times with ethyl acetate. The combined organic phases were dried over sodium sulfate and concentrated in vacuo. Flash chromatography (¼ ethyl acetate/hexane) afforded 2.00 g (60%) 4-(4-methoxy-3-nitro-phenyl)-3,6-dihydro-2H-pyran (VIII) as a light yellow solid. ES-MS m/e (%): 253 (M+NH4+, 100), 236 (M+H+, 24).
