反应详情

To a suspension of 4-ethyl-3-nitrobenzoic acid methyl ester (11d) (10 g, 48 mmol) and paraformaldehyde (1.8 g, 60 mmol) in DMSO (10 mL) was added in portions potassium tert-butoxide (1.46 g, 12 mmol), during which the colour of the reaction mixture was changing from yellow to purple. After stirring for 2.5 hours at room temperature, the reaction mixture was directly applied to the silica gel bed of a chromatography column (100 g silica, 3.5×14 cm) and eluted with hexane/ethyl acetate (EA) (3:1, v/v). The slightly yellow product (4d) was obtained in 38% yield (4.42 g, 18 mmol). Rf=0.24 (hexanes/EtOAc 7:3). 1H NMR (250 MHz, CDCl3) δ 8.36 (d, 1H, arom. H(3)), 8.18 (dd, 1H, arom. H(5)), 7.58 (d, 1H, arom. H(6)), 3.93 (s, 3H, COOCH3), 3.78 (m, 2H, α-CH2), 3.54 (sextet, 1H, β-CH), 1.69 (d, 3H, CH3).

1. washeluted with hexane/ethyl acetate (EA) (3:1