Synthesis
Step 1: Preparation of ethyl 4-chloro-3-nitrobenzoate
4-Chloro-3-nitrobenzoic acid (300 g) was dissolved in ethanol (1500 mL) and concentrated sulfuric acid (100 mL) was added slowly under ice bath cooling. The reaction mixture was heated to reflux for 7 hours. After completion of the reaction, the mixture was poured into ice water and the precipitated crystals were collected by filtration to afford the target product ethyl 4-chloro-3-nitrobenzoate (332 g, 97% yield).
1H-NMR (300 MHz, CDCl3): δ 8.50 (1H, d, J = 2.1 Hz), 8.16 (1H, dd, J = 8.4, 2.1 Hz), 7.63 (1H, d, J = 8.4 Hz), 4.43 (2H, q, J = 7.5 Hz), 1.42 (3H, t, J = 7.5 Hz).
References
[1] Patent: US2003/50320, 2003, A1
[2] Patent: WO2004/29050, 2004, A1. Location in patent: Page 105;106
[3] Synthetic Communications, 2002, vol. 32, # 11, p. 1703 - 1707
[4] Patent: US6204264, 2001, B1
