Sodium hydride → methyl (E)-4-(4-amino-6-chloro-pyrimidin-2-yl)sulfanyl-3-methyl-but-2-enoate

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Reaction Steps

To (E)-4-hydroxy-3-methyl-2-butenoic acid methyl ester (0.75 g, 5.76 mmol) in methylene chloride cooled to -15° C. in a flame dried flask is added dibromotriphenylphosphorane (2.68 g, 6.34 mmol). The reaction is stirred at -15° C.-0° C. for two hours, quenched by addition of ice (10 ml), extracted with methylene chloride (2×10 ml), washed with saline (10 ml), dried over sodium sulfate, concentrated in vacuo, and chromatographed on silica gel (230-400 mesh, 100 ml), eluting with hexane/ethyl acetate (95/5). The appropriate fractions are combined and concentrated in vacuo to give (E)-4-chloro-3-methyl-2-butenoic acid methyl ester. 4-Amino-6-chloro-2-mercaptopyrimidine mesylate (0.30 g, 1.16 mmol) is dissolved in DMF (4 ml) and sodium hydride (0.06 g, 2.56 mmol) at ambient temperature followed by the addition of (E)-4-bromo-3-methyl-2-butenoic acid methyl ester (0.22 g, 1.16 mmol). The reaction is stirred for 15 hours, quenched with excess water, extracted with ethyl acetate (3×20 ml). The extracts are combined, washed with saline (20 ml), dried over sodium sulfate, concentrated in uacuo and chromatographed on silica gel (230-400 mesh, 100 ml), eluting with hexane/ethyl acetate (80/20). The appropriate fractions are combined (Rf =0.43, TLC, hexane/ethyl acetate, 50/50) and concentrated in vacuo to give the title compound, mp 134-136° C.

Provenance & Evidence