A stirred solution of 4 (13.20 g, 27.2 mmol) and dimethyl malonate (5.39 g, 40.8 mmol) in DMF (85 mL) was cooled to -5° C. and treated with powdered K2CO3 (22.53 g, 163 mmol). The mixture was allowed to warm to 20° C. over a 2 h period, and after stirring for a further 12 h at 20° C. was poured slowly into cold stirred 0.5N HCl (1750 mL). The resulting solid was dissolved in CH2Cl2 and the solution was washed twice with water, dried (Na2SO4) and then evaporated to dryness. The residue was crystallised from CH2Cl2 /iPr2O/petroleum ether to give 4-methoxybenzyl 1-[di(methoxycarbonyl)methyl]-4-nitronaphthalene-2-carboxylate (5) (10.66 g, 84%), suitable for further use. A sample recrystallised from MeOH had mp 124-125° C. 1H NMR (CDCl3) δ 8.62 (s, 1H, H-3), 8.45 (d, J=8.6 Hz, 1H, H-5), 8.21 (d, J=8.7 Hz, 1H, H-8), 7.70 (br t, J=7.7 Hz, 1H, H-6), 7.69 (br t, J=7.8 Hz, 1H, H-7), 7.41 (d, J=8.7 Hz, 2H, H-2',6'), 6.94 (d, J=8.7 Hz, 2H, H-3',5'), 6.62 (s, 1H, ArCH), 5.37 (s, 2H, CH2), 3.83 (s, 3H, PhOCH3), 3.69 (s, 6H, 2×CO2CH3). Anal. Calculated for C24H21NO9 : C, 61.6; H, 4.7; N, 3.1%.
