Lithium hydroxide, monohydrate → 2-Vinyl-morpholine-2,4-dicarboxylic acid 4-tert-butyl ester

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A solution of crude 2-vinyl-morpholine-2,4-dicarboxylic acid 4-tert-butyl ester 2-methyl ester (3.284 mmol) in tetrahydrofuran/methanol/water (50 mL, 2:2:1) was treated with lithium hydroxide monohydrate (413.3 mg, 9.852 mmol). After stirring at room temperature for 2 h, the volatiles were removed in vacuo and the residue was cooled to 0° C. and quenched with hydrochloric acid (1 M). The aqueous layer was extracted with dichloromethane (2×). The combined organics were filtered through a phase separator and the volatiles were removed in vacuo to provide the title compound (761.4 mg, 90% over 2 steps) as colorless needles. 1H NMR (300 MHz, CDCl3) δ 1.48 (s, 9H), 3.31-3.42 (m, 1H), 3.45-3.61 (m, 2H), 3.87-3.94 (m, 2H), 4.02 (d, J=13.6 Hz, 1H), 5.44 (d, J=10.7 Hz, 1H), 5.60 (d, J=17.4 Hz, 1H), 5.85 (dd, J=17.4, 10.7 Hz, 1H).

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