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0 °C

A solution of 2-chloro-5-nitrobenzoic acid (10.14 g, 50.3 mmol), thionyl chloride (4.4 mL, 60 mmol) and DMF (4 drops) in 1,2-dichloroethane (150 mL) was stirred at reflux for 14 h, cooled and evaporated. The acid chloride was dissolved in THF (100 mL), cooled to 0° C., and a solution of potassium t-butoxide (5.57 g, 50 mmol) in THF (150 mL) added dropwise over 30 min under nitrogen. The mixture was stirred a further 15 min at 0° C., diluted with aq. NaHCO3, extracted with EtOAc (×2), and the extracts dried (Na2SO4) and evaporated. Crystallisation from petroleum ether gave t-butyl 2-chloro-5-nitrobenzoate as a white crystalline solid (10.1 g, 78%), mp 91.5-92° C. 1H NMR (CDCl3) δ8.59 (d, J=2.8 Hz, 1H, H-6), 8.24 (dd, J=8.8, 2.8 Hz, 1H, H-4), 7.63 (d, J=8.8 Hz, 1H, H-3), 1.65 (s, 9H, t-Bu); 13C NMR (CDCl3) d 163.0 (CO2tBu), 146.1, 140.0, 133.3, (C-1,2,5), 132.0, 126.1, 126.0 (C-3,4,6), 84.0 (CMe3), 28.1 (CH3). Anal. Calculated for C11H12ClNO4 : C, 51.3; H, 4.7; N, 5.4; Cl, 13.8. Found: C, 51.3; H, 4.5; N, 5.6; Cl, 14.0%.

1. temperatureat reflux for 14 h
2. temperaturecooled
3. customevaporated
4. dissolutionThe acid chloride was dissolved in THF (100 mL)
5. extractionextracted with EtOAc (×2)
6. dry with materialthe extracts dried (Na2SO4)
7. customevaporated
8. customCrystallisation from petroleum ether