Ammonia → [2-[(2-Amino-3,4-dioxo-1-cyclobuten-1-yl)amino]ethyl]phosphonic acid diethyl ester

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Reaction Steps

A solution of [2-[(2-ethoxy-3,4-dioxo-1-cyclobuten-1-yl)amino]ethyl]phosphonic acid diethyl ester (1.69 g, 5.5 mmol) in 100% ethanol (40 mL) was placed in flask equipped with an addition funnel and a nitrogen inlet. Saturated ethanolic ammonia (190 mL) was placed in the addition funnel and added dropwise over 1 hour. The reaction mixture was left stirring at room temperature for a total of 24 hours and then concentrated in vacuo. The resulting solid was recrystallized from methanol in ethyl acetate to afford [2-[(2-amino-3,4-dioxo-1-cyclobuten-1-yl)amino]ethyl]phosphonic acid diethyl ester as a yellow solid (1.27 g, 82%, mp=150°-152° C. dec); IR (KBr, cm-1): 1805, 1650; MS (+FAB): 277 (MH+, 100), 182 (20), 109 (15); 1H NMR (DMSO, 400 MHz): δ 7.5 (br s, 3 NH), 4.1-3.9 (m, 4H), 3.7-3.6 (m, 2H), 2.11 (d of t, J=17.5 and 7.5 Hz, 2H), 1.22 (t, 6H).

Provenance & Evidence