Thiosalicylic acid (Sigma Aldrich)

Anhydrous DMF (Sigma Aldrich)

4-Fluoronitrobenzene (Sigma Aldrich)

Potassium Carbonate (Sigma Aldrich)

Methylated spirits (Fisher Scientific)

A mixture of thiosalicylic acid (5.14 g, 33.34 mmol) and potassium carbonate (13.7 g, 99.13 mmol) in anhydrous DMF (75 mL) was stirred for 10 minutes at room temperature.*  To the reaction mixture was added 4-fluoronitrobenzene (5.63 g, 39.9mmol) dissolved in anhydrous DMF (10 mL).  The reaction mixture was heated to 130°C for 8 hours.**  Upon cooling, the reaction mixture was poured into ice (250 g) and acidified with 6M HCl (aq) to pH=4 giving a yellow solid.***  The crude solid was washed with water and petroleum ether and then it was recrystallized in the minimum amount of methylated spirits.  The crystals produced were isolated and dried at the vacuum pump to yield 2-(4-nitrophenylthio)benzoic acid (7.33 g, 80%) as a yellow solid.

*Round bottom flask fitted with a reflux condenser was used which fitted snugly into a metal heating block.  A thermocouple was used to control the temperature and reaction was open to the air (no inert gasses were required).  Stirring was accomplished using a stirring bar which was controlled from the hot plate.  The whole reaction was accomplished in the open air without the need of dry/inert conditions.

** Reaction monitored by TLC on silica plates using petroleum ether 40-60 (1:1) ethyl acetate with a few drops of acetic acid (roughly 1% of the total volume) as solvent.

***pH determined using universal indicator paper.

¹H NMR (400 MHz, DMSO-d₆) δ 8.21 (d, J = 8.9 Hz, 1H), 7.93 (dd, J = 7.7, 1.6 Hz, 1H), 7.57 (d, J = 8.9 Hz, 1H), 7.54 – 7.45 (m, 1H), 7.41 (td, J = 7.5, 1.3 Hz, 1H), 7.18 (dd, J = 7.9, 1.2 Hz, 1H).  ¹³C NMR (101 MHz, DMSO) δ 167.93, 146.88, 144.76, 135.78, 133.03, 132.36, 132.28, 131.58, 131.15, 127.81, 124.92.  LCMS m/z: 274 [M-] FTIR (cm^-1): 2845.86, 1667.40, 1597.96, 1514.02, 1460.82, 1409.17, 1342.49, 1249.97, 1058.32, 1039.01, 903.06, 851.99