Yield: 98%

Reaction Conditions:

with sulfuric acid;nitric acid at 0 - 20; for 16.5 h;

Steps:

A
Step A To a suspension of 2,4-difluorobenzoic acid (9.985 g, 63.2 mmol) in concentrated sulfuric acid (30 mL) at 0° C. was added fuming nitric acid (30 mL) over 30 min. The mixture was allowed to warm to RT and stirred for an additional 16 h. The homogeneous mixture was poured onto ice and extracted with ethyl acetate. The organic extract was washed with water, dried and concentrated in vacuo to afford 2,4-difluoro-5-nitrobenzoic acid (12.56 gm, 98%) as pale yellow solid.

References:

Borzilleri, Robert M.;Bhide, Rajeev S.;Tokarski, John S.;Zheng, Peter;Qian, Ligang;Cai, Zhen-Wei US2004/77696, 2004, A1 Location in patent:Page/Page column 9