Hydrochloric Acid → 1-methylethyl (2E)-2-butenoylcarbamate

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Isopropyl carbamate (30 g, 291 mmol, available from TCI) was charged to a 3 L Lara vessel and dry tetrahydrofuran (THF) (150 ml) added. (2E)-2-Butenoyl chloride (31.2 ml, 326 mmol, available from Aldrich) was added under nitrogen and the jacket cooled to −30° C. When the solution temperature reached −17° C. Lithium tert-butoxide (1M, 655 mL, 655 mmol) was added by peristaltic pump over 2 h, keeping the reaction temperature between −10° C. and −18° C. Once the addition was complete the mixture was stirred for 30 min and brought to 0° C. Diethyl ether (450 ml) and hydrochloric acid (1M, 375 mL) were added and the mixture brought to 20° C. with vigourous stirring. The stirring was stopped, the layers allowed to separate and the aqueous layer run off. Brine (375 mL) was added and the mixture stirred vigourously. The stirring was stopped, the layers allowed to separate and the aqueous layer run off. The organic layer was dried (MgSO4), filtered and evaporated to a brown oil (60 g). The was applied to a silica column (40+M Biotage) and eluted with DCM/ethyl acetate (1:1 to 0:1, 10 CV). The product containing fractions were evaporated to dryness and loaded on to a Redisep Isco silica column (1500 g) and eluted with a gradient ethyl acetate in cyclohexane (0-40%). The clean, product containing fractions were evaporated to an off-white solid (15.41 g). LCMS (Method C): Rt=0.68, MH+=172

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