Diethyl squarate → HCID 10553302, compound

Participants

Reaction Steps

A solution of [3-[[2-(diethoxyphosphinyl)ethyl]amino]propyl]carbamic acid phenylmethyl ester (3.17 g, 8.5 mmol) in absolute ethanol (40 mL) was added over 45 minutes to 3,4-diethoxy-3-cyclobutene-1,2-dione (2.3 mL, 16 mmol) dissolved ethanol (55mL). After leaving overnight, the reaction mixture was preadsorbed onto silica gel and purified by flash chromatography (7 cm diameter, gradient elution was 2.5-10% methanol in dichloromethane) to yield [3-[[2-(diethoxyphosphinyl)ethyl](2-ethoxy-3,4-dioxo-1-cyclobuten-1-yl)amino]propyl]carbamic acid phenylmethyl ester as a viscous oil (3.75 g, 89%); 1H NMR (CDCl3, 400 MHz): δ 7.35 (m, 5H), 5.45 (br m, NH), 5.09 (s, 2H), 4.80-4.71 (m, 2H), 4.16-4.09 (m, 4H), 3.90-3.48 (m, 4H), 3.23-3.20 (m, 2H), 2.16-2.05 (m, 2H), 1.85-1.79 (m, 2H), 1.47, 1.41 (t, J=7 Hz, 3H), 1.34 (t, J=7 Hz, 6H).

Provenance & Evidence