Br[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[Mg:8].[C:9](=[S:11])=[S:10].[Br:12][C:13]([CH3:20])([CH3:19])[C:14]([O:16][CH2:17][CH3:18])=[O:15]>C1COCC1>[C:2]1([Mg:8][Br:12])[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[C:9]([S:11][C:13]([C:14]([O:16][CH2:17][CH3:18])=[O:15])([CH3:20])[CH3:19])(=[S:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1Phenyl magnesium bromide was prepared from bromobenzene (6.28 g, 0.04 mol) and magnesium turnings (1 g) in dry THF (30 mL). The solution was warmed to 40° C. and carbon disulfide (3.05 g, 0.04 mol) was added over 15 minutes while maintaining the reaction temperature at 40° C. To the resultant dark brown solution was added ethyl a-bromoisobutyrate (7 g, 0.036 mol). The reaction temperature was raised to 80° C. and maintained for 60 hours. Ice water (50 mL) was added and the organic products were extracted with diethyl ether (3×50 mL). The combined organic extracts were washed with water, brine and dried over anhydrous magnesium sulfate. After removal of solvent and purification by column chromatography (Kieselgel-60, 70-230 mesh, n-hexane/diethyl ether (9:1) eluent), 2-(ethoxycarbonyl)prop-2-yl dithiobenzoate was obtained as a red oil (4.52 g, 42.2% yield). 1H-nmr (CDCl3) d (ppm): 1.25 (t, 3H, CH2CH3), 1.77 (s, 6H, 2×CH3), 4.17 (q, 2H, OCH2CH3), 7.35 (dd, 2H, meta-ArH), 7.52 (dd, 1H, para-ArH) and 7.95 (d, 2H, ortho-ArH).
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