2,2-Dimethoxypropane → 3-tert-Butyl 4-methyl 2,2-dimethyl-1,3-oxazolidine-3,4-dicarboxylate

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Reaction Steps

To a solution of (34) in CH2Cl2, stirring under nitrogen at 0° C., was added 2,2-dimethoxypropane (29.5 mL, 237.9 mmol) and p-toluene sulfonic acid monohydrate (9.050 g, 47.58 mmol). The mixture was removed from the ice bath after 15 minutes and stirred at room temperature for 1.5 hours. The reaction mixture was poured into 50 mL of saturated NaHCO3 (aq) and extracted with diethyl ether (3×50). The organic layer was extracted with NaHCO3 and brine, then dried over anhydrous MgSO4, filtered and concentrated under reduced pressure. The crude material was purified by flash chromatography on SiO2 (1:1 EtOAc/Hexanes) to yield 7.659 g (62%, 3 steps) of a clear liquid.

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