A sealed pressure flask, flushed with N2, containing a mixture of 4-bromo-benzoic acid ethyl ester (3a) (5 g, 0.0218 mol), ethoxyphosphinoylmethyl-phosphonic acid diethyl ester (3b), (5.86 g, 0.024 mol), NMM (2.88 mL, 0.0262 mmol) and Pd(PPh3)4 (2.017 g, 0.00175 mol) in acetonitrile (20 mL) was stirred at ambient temperature for 5-10 min, then heated at 90° C. for 18 hours. The reaction mixture was filtered through celite, and the celite was washed with EtOAc (3×30 mL) until the filtrate showed little or no evidence of product by HPLC. The combined organics were dried over Na2SO4 and concentrated on rotary evaporator. The desired product (ix) was purified by silica gel flash chromatography to give a pale yellow oil (5.01 g). 1H NMR (300 MHz, CDCl3) δ (ppm)): 0.96 (t, J=7.07 Hz, 3H), 1.13 (m, 9H), 2.41 (t, J=18.2 Hz, 2H), 3.84 (m, 6H), 4.17 (q, J=7.11 Hz, 2H), 7.71 (m, 2H), 7.92 (m, 2H), 31P NMR (121 MHz, CDCl3) δ 32.8 and 19.7.
