Diethyl squarate → HCID 10552641, compound

Participants

Reaction Steps

To a solution of 3,4-diethoxy-3-cyclobutene-1,2-dione (5.0 mL, 34 mmol) in absolute ethanol (180 mL) prepared under nitrogen, was added a solution of [3-[[2-(diethoxyphosphinyl)ethyl]amino]-2-hydroxypropyl]carbamic acid 1,1-dimethylethyl ester (12.11 g, 34 mmol) in ethanol (60 mL) over 1 hour. The reaction mixture was stirred at room temperature overnight and then concentrated in vacuo. The residue was dissolved in chloroform (150 mL), preadsorbed onto silica gel, and purified by flash chromatography (7 cm diameter, gradient elution with 2.5-15% methanol in dichloromethane) to yield [3-[[2-(diethoxyphosphinyl)ethyl](2-ethoxy-3,4-dioxo-1-cyclobuten-1-yl)amino]-2-hydroxypropyl]carbamic acid 1,1-dimethylethyl ester as a clear viscous oil (11.34 g, 70%; IR (neat, cm-1):3350, 1800, 1700: 1H NMR (CDCl3 400 MHz): δ 5.37, 5.19 (br s, NH), 4.82-4.72 (m, 3H), 4.16-3.11 (m, 11H), 2.24-2.14 (m, 2H), 1.47-1.43 (m, 12H), 1.32 (t, J=7 Hz, 6H).

Provenance & Evidence