Triethylamine → Tert-butyl 2,6-dioxomorpholine-4-carboxylate

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Reaction Steps

Iminodiacetic acid (5.0 g, 37.6 mmol) in THF-water (1:1, 100 ml) was treated with Na—HCO3 (12.6 g, 150 mmol) portion-wise over 15 minutes. Boc anhydride (9.85, 45.1 mmol) was added and the mixture was stirred at room temperature for 2 days. THF was removed by evaporation in vacuo and the aqueous solution was washed with ether (2×), acidified using conc. HCl to pH 1 under cooling with ice bath and extracted with AcOEt (3×). The organic phase was washed with brine, dried (Na2SO4) and evaporated in vacuo to yield 2.55 g (29%). Crude N-Boc-iminodiacetic acid (2.0 g, 8.6 mmol) was dissolved in AcOEt (100 ml), cooled to 0° C., and treated with triethylamine (2.43 ml, 17.4 mmol) and powdered triphosgene (0.84 g, 2.83 mmol). The suspension was stirred 15 minutes under cooling, and 15 minutes at room temperature. The solution was washed with brine, dried (MgSO4) and evaporated in vacuo to yield 17, 1.53 g (83%).

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