2-Fluoro-5-( Methylthio)benzoic Acid synthesis

Yield:57318-98-6 76%

Reaction Conditions:

Stage #1: p-fluorothioanisolewith n-butyllithium in tetrahydrofuran at -60; for 1 h;
Stage #2: carbon dioxide in tetrahydrofuran at 20; for 3 h;

Steps:

62

To a cooled (-60 °C) solution of Scheme 54 compound 1 (5.0 g, 35.66 mmol) in dry THF (50 mL) was added nBui (21.9 mL, 35.66 mmol, 1.6 M in THF) dropwise. The reaction mixture was stirred at -60 °C for 1 h after which time C0₂ gas was passed through while the solution was allowed to warm to RT and stirred for 3h. After TLC showed the starting material was completely consumed, the mixture was quenched with water (20 mL) and extracted with ethyl acetate (2 x 30 mL). The organic layer was washed with brine (10 mL), dried over anhydrous Na₂S0₄ then filtered and concentrated to give a residue which was purified by flash chromatography on silica gel (eluting with petroleum ether/EtOAc 100/0 gradually increasing to 80/20) to give Scheme 54 compound 2 (5 g, 76%) as an off-white solid. MS [ESI, (M-H)^"] = 185.3.

References:

WO2014/52365,2014,A1 Location in patent:Page/Page column 295