Nitrogen → 4-(Acetyloxy)-3-methoxybenzyl 2-thioxo-1,3-thiazolidine-3-carboxylate

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Reaction Steps

To a flask purged with N2 was added 2-mercaptothiazoline (MTA) (167 mg, 1.1×1.27 mmol) and polyvinyl pyridine (PVP) (159 mg, 8.8 mg/eq, 1.1×1.27 mmol) (see Scheme 1). Seven mL of dry CH2Cl2 (5 mL/mmol MTA) were added to the flask while maintaining a positive N2 pressure. The suspension was stirred at room temperature, and diphosgene (137 mg, 85 μL, 0.55×1.27 mmol) was added dropwise. After being stirred for five hours the intermediate chloroformylthiazolidine (VI) was filtered through a sintered glass filter into a flask containing the benzyl alcohol, I, (250 mg, 1.27 mmol) dissolved in 1-2 mL of dry CH2Cl2. The beads of PVP thus removed were rinsed in portions with a total of 5 mL of fresh, dry CH2Cl2. The flask containing the filtrate was placed under a positive N2 pressure and immersed in an ice bath. To the cooled solution was added NEt3 (141 mg, 195 μL, 1.1×1.27 mmol) directly into the stirred solution, via syringe. After stirring overnight the diluted reaction solution was extracted with 1N HCl, water and saturated NaCl. The organic layer was dried over MgSO4, filtered and concentrated. The crude product was purified twice by column chromatography on silica gel eluting with dichloromethane/methanol (98:2, v/v) to give 160 mg (37%) of VII as a nearly pure yellow solid (compound appears to decompose slightly while on the column); Rf=−0.62 (dichloromethane/methanol, 98:2, v/v); 1HNMR (CDCl3) δ 7.11 (d, 4J=1.65 Hz, 1H), 7.01-6.99 (m, 1H), 6.98-6.95 (m, 1H), 5.27 (s, 2H), 4.52 (t, 3J=7.5 Hz), 3.82 (s, 3H), 3.29 (t, 3J=7.5 Hz, 2H) and 2.30 (s, 3H). Exact mass (ESI) calculated for C14H15NNaO5S2 [M+Na] 364.0284. found 364.0277.

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