2-​Hydroxy-9H-thioxanthen-​9-​one (prepared in house, see Synthetic Page 868)

4-Toluenesulphonyl chloride (Sigma Aldrich)

Triethylamine (Sigma Aldrich)

To a round bottomed flask was added 2-hydroxy-9H-thioxanthen-​9-​one (0.46 g, 2 mmol), DCM (20 mL) and 4-toluenesulphonyl chloride (0.95 g, 5 mmol).*  The solution was lowered into an slush bath** and with constant stirring, triethylamine (1.01 g, 10 mmol) was added dropwise over a period of 5 minutes.***  Upon the total addition of triethylamine, the solution was allowed to stir for 90 minutes at room temperature.  The reaction mixture was poured into a separating funnel and DCM (50 mL) was added.  The organic layer was washed with 2M hydrochloric acid (100 mL), the organic layer was isolated, dried with anhydrous sodium sulphate and evaporated under reduced pressure.  The solid was recrystallised from hot toluene to yield 2-​tosyloxy-9H-thioxanthen-​9-​one (0.61 g, 80%) as yellow flakes.  

*4-Toluenesulphonyl chloride was purified by hot recrystallisation using 40-60ºC petroleum ether before use to remove any tosic acid.  Note the 40-60ºC petroleum ether was boiling and the solution was hot filtered.

**Slush bath made from ice and water to ensure total surface contact.

***Note that a slight temperature rise is seen upon the addition of triethylamine but this was easily controlled using a slush bath. 

¹H NMR (400 MHz, DMSO-d6) δ 8.40 (dd, J = 8.1, 1.4 Hz, 1H), 8.00 (d, J = 2.7 Hz, 1H), 7.88 (d, J = 8.8 Hz, 1H), 7.85 – 7.74 (m, 4H), 7.58 (ddd, J = 8.2, 6.9, 1.4 Hz, 1H), 7.52 – 7.43 (m, 3H), 2.42 (s, 3H). ¹³C NMR (101 MHz, DMSO) δ 178.41, 147.84, 146.61, 136.73, 136.03, 133.76, 131.53, 130.82, 129.85, 129.54, 129.32, 128.77, 127.99, 127.66, 127.59, 127.06, 122.00, 21.65. LCMS 382.08 [M⁺].

Smith R.B., Cunningham I.D., The synthesis and catalytic epoxidation activity of a range of substituted iron porphyrins, University of Surrey Ph.D, 2008.