p-Hydroxythiophenol was extracted with AcOEt (0.5 mL, 18 times, typically each min for the first 10 min of reaction, then each 5 min and one before RP-HPLC purification). The extraction of phydroxythiophenol was monitored by spotting the organic phases on a silica gel plate for thin layer chromatography and reading the plate under 254 nm UV light.