Iodine → Benzoic acid, 3-mercapto-

Temperature

110 °C

3-Chlorosulfonylbenzoic acid (156.0 g, 0.707 mol), acetic acid (240 mL), and red phosphorus (78.5 g, 2.53 mol) were placed in a 2-L three-neck flask. The mixture was heated to 110° C. and stirred while a solution of iodine (2.82 g, 0.011 mol) in acetic acid (66 mL) was added dropwise over about 30 min, so as to maintain the color of iodine vapor. The stirred mixture was cooled to 100° C. and treated dropwise with 41 mL (2.3 mol) of water over a 10-min period, then heated at reflux temperature for 1.5 h and subsequently cooled to 90° C. Following the addition of saturated sodium chloride solution (250 mL) and water (500 mL), the mixture was kept at 0-5° C. for 1 h and filtered. The damp filter cake was slurried with 450 mL of acetone, and the excess red phosphorus was removed by filtration; then the acetone was evaporated from the filtrate while adding 500 mL of water. The resultant solid was filtered off and dried under vacuum to give 100.1 g (92%) of 3-mercaptobenzoic acid, mp 138-141° C. (lit. mp 138-141° C.); 1H NMR (400 MHz, in CDCl3 w/TMS, ppm) 3.59 (s, SH), 7.36 (t, J=7.8 Hz, H-5), 7.51 and 7.90 (2d, J=7.8 Hz, H-4 and H-6), 8.03 (s, H-2); {1H}13C NMR (100 MHz, in CDCl3 w/TMS, ppm) 171.77 (C═O), 134.49 (C-4), 132.24 (C-1), 130.86 (C-2), 130.34 (C-3), 129.42 (C-5), 127.59 (C-6).

1. additionwas added dropwise over about 30 min
2. temperatureThe stirred mixture was cooled to 100° C.
3. temperatureheated
4. temperatureat reflux temperature for 1.5 h
5. temperaturesubsequently cooled to 90° C
6. filtrationfiltered
7. customthe excess red phosphorus was removed by filtration
8. customthen the acetone was evaporated from the filtrate
9. additionwhile adding 500 mL of water
10. filtrationThe resultant solid was filtered off
11. customdried under vacuum

ORD record

ord-ea35cf69eece4686a0f933f2a9cf9ac2

Source dataset

uspto-grants-2004_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06747081B2