(4-Fluorophenyl)dimethylphosphine oxide → 1-(Dimethyl-phosphinoyl)-4-nitro-benzene

Participants

Reaction Steps

A sealed pressure flask, flushed with N2, containing a mixture of 3.90 g (22.7 mmol) of 1-(Dimethyl-phosphinoyl)-4-fluoro-benzene and 6.0 g (113.3 mmol) of LiNO2 (for prep see, W. C. Ball and H. H. Abram J. Chem. Soc. 1913, 103, 2130-2134) in 27 mL of DMPU (1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone) was stirred at ambient temperature for 5-10 min (to dissolve fluoro compound) then heated at 190° C. for 3 days. The resulting dark brown solution was cooled to ambient temperature, diluted with 300 mL of brine, then extracted with EtOAc (10×100 mL) until the aqueous layer showed little or no evidence of product by HPLC. The combined organics were dried over MgSO4 and concentrated. The excess DMPU was removed via short-path distillation (120° C./0.3 mm) to provide a semi-solid, which was dissolved in a minimum amount of iPrOH and purified by silica gel flash chromatography (eluted with 5% iPrOH/DCM, then 10% iPrOH/DCM, then 15% iPrOH/DCM) to provide 2.04 g of an yellow solid: 1H NMR (300 MHz, DMSO-d6) δ 8.34 (dd, J=8.7, 1.9 Hz, 2H), 8.07 (dd, J=10.6, 8.8 Hz, 2H), 1.75 (s, 3H), 1.70 (s, 3H). 31P NMR (121 MHz, DMSO-d6) δ 37.89.

Provenance & Evidence