[H-].[Na+].[C:3]1([SH:9])[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1.[C:10]1(=[O:15])[O:14][CH2:13][CH2:12][CH2:11]1.[OH-].[Na+]>C1COCC1.O>[C:3]1([S:9][CH2:13][CH2:12][CH2:11][C:10]([OH:15])=[O:14])[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1To a suspension of sodium hydride (60% in mineral oil, 10.4 g, 0.26 mol) in anhydrous THF (400 mL) at ambient temperature is added thiophenol (26 g, 0.23 mol) dropwise via syringe. The resulting white suspension is stirred for 30 minutes under a nitrogen atmosphere then γ-butyrolactone (22.4 g, 0.26 mol) is added. The mixture is warmed to gentle reflux and stirred for 6 hours after which it became a solid mass and is allowed to cool to room temperature and stand overnight. The mixture is dissolved in water (1200 mL) containing 1 N NaOH (100 mL) and is extracted with diethyl ether (2×500 mL). The aqueous layer is acidified with 1N HCl and extracted with diethyl ether (3×500 mL). The organic extracts are washed with brine (300 mL) then dried over MgSO4, filtered and concentrated to afford a white solid which is chromatographed on silica gel (pet-ether/EtOAc, 19:1→9:1) to afford 4-phenylsulfanylbutanoic acid (36.6 g, 79%) as a white solid. TLC analysis [pet-ether/EtOAc, 1:1, Rf (thiophenol)=0.90, Rf (acid)=0.50]. m.p. 73-74° C.; 1H NMR (300 MHz, CDCl3) δ 1.95 (quint, J=7.1 Hz, 2H), 2.52 (t, J=7.2 Hz, 2H), 2.97 (t, J=7.1 Hz, 2H), 7.1-7.3 (m, 5H) ppm. Mass spectrum (EI) m/z 196 (M)+.
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