Methyl iodide → 4-tert-Butyl 2-methyl morpholine-2,4-dicarboxylate

Methyl iodide (9.38 ml, 150 mmol) was added to a suspension of 4-(tert-butoxycarbonyl)-2-morpholinecarboxylic acid (14.5 g, 62.6 mmol) and dry potassium carbonate (17.3 g, 125 mmol) in dry dimethylformamide (DMF) (360 ml). The mixture was stirred over night, filtered through Celite and concentrated. The residue was partitioned between dichloromethane and water. The organic phase was dried over magnesium sulfate and concentrated to give 22 g of crude product.