Carbon Disulfide → Diethyl 2-[bis(4-methoxybenzylsulfanyl)methylene]malonate

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A solution of dimethylformamide (50 mL) containing diethyl malonate (12.78 g, 0.08 mol) is added slowly to an ice-cooled suspension of sodium hydride (60% dispersion in mineral oil, 6.53 g, 0.16 mol) in dimethylformamide (500 mL). The rate of addition of diethyl malonate is such as to maintain the temperature of the reaction mixture below 5° C. After the addition of diethyl malonate is complete, the gray reaction mixture continues to stir at 0° C. for 15 min. Carbon disulfide (14.5 mL, 0.24 mol) is then added dropwise to give a red mixture that is allowed to warm to room temperature with stirring for 1 h. A solution of dimethylformamide (25 mL) containing 4-methoxybenzyl chloride (25.00 g, 0.16 mol) is added dropwise to the reaction mixture at room temperature. The resulting orange mixture is allowed to warm to room temperature with stirring for 15 h, diluted with water (500 mL), and extracted with ethyl acetate (4×500 mL). The combined extracts are concentrated under reduced pressure (˜1 L), washed with water (3×150 mL), washed with brine (3×150 mL), dried over magnesium sulfate, and evaporated under reduced pressure to give crude 1. The crude product is purified by flash column chromatography (eluting with ethyl acetate/hexanes=1:4; Rf 0.21) to give 1 as a yellow solid. mp 57-59° C. 1H NMR (CDCl3): δ 1.27 (t, J=7.0 Hz, 3H, CO2CH2CH3), 3.79 (s, 3H, OCH3), 4.07 (s, 2H, SCH2), 4.23 (q, J=7.0 Hz, 2H, CO2CH2CH3), 6.83 (m, 2H, H-3/H-5), 7.20 (m, 2H, H-2/H-6). 13C{1H} NMR (CDCl3): δ 14.0 (CO2CH2CH3), 40.3 (SCH2), 55.3 (OCH3), 61.4 (CO2CH2CH3), 114.1 (aromatic C-3/C-5), 128.1 (═C—CO2CH2CH3 or C—CH2S—), 128.7 (═C—CO2CH2CH3 or C—CH2S—), 130.4 (aromatic C-2/C-6), 155.6 (—CH2S—C═), 159.1 (aromatic C-4, C—OCH3), 163.9 (CO2CH2CH3). LCMS m/z calcd for C24H28O6S2 476 ([M+]). found 477 ([M+H]+). HRMS m/z calcd for C24H28NaO6S2 499.1225 ([M+Na]+). found 499.1230. Anal. Calcd for C24H28O6S2: C, 60.48; H, 5.92; S, 13.46. Found: C, 60.51; H, 5.97; S, 13.19.

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