Diethyl squarate → HCID 10806855, compound

Participants

Reaction Steps

A solution of 3,4-diethoxy-3-cyclobutene-1,2-dione (2.6 mL, 18 mmol) in absolute ethanol (90 mL) was treated with [3-(cyanomethylamino)propyl]carbamic acid 1,1-dimethylethyl ester (3.90 g, 18 mmol) in ethanol (30 mL) over 90 min. After 40 hours the reaction mixture was evaporated, dissolved in dichloromethane, preadsorbed onto silica gel, and purified by flash chromatography (7 cm diameter, gradient elution with 0-5% methanol in dichloromethane) to yield [3-[(cyanomethyl)-(2-ethoxy-3,4-dioxo-1-cyclobuten-1-yl)amino]propyl]carbamic acid 1,1-dimethylethyl ester as a yellow oil (5.48 g, 90%); IR (neat, cm-1): 3360, 1800; MS (+FAB): 282 (76), 238 (98), 158 (100); 1H NMR (CDCl3, 400 MHz): δ 4.81 (q, J=7 Hz, 2H), 4.75 (br s, NH), 4.45, 3.66 (s, 2H), 3.84, 3.60 (br m, 2H), 3.26-3.15 (m, 2H), 1.91 (p, J=6.5 Hz, 2H), 1.50 (t, J=7 Hz, 3H), 1.45 (s, 9H).

Provenance & Evidence