Diethyl squarate → 4-(2-Ethoxy-3,4-dioxo-cyclobut-1-enylamino)-3-ethylbenzonitrile

Participants

Reaction Conditions

Reaction Steps

4-Amino-3-ethylbenzonitrile (0.86 g, 5.88 mmol) and 3,4-diethoxy-3-cyclobutene-1,2-dione (1.0 g, 5.88 mmol) in acetonitrile (2 mL) was heated in an oil bath at 110° C. for 21 hours. 3,4-Diethoxy-3-cyclobutene-1,2-dione (0.5 g, 2.9 mmol) was added to the reaction mixture and the temperature of the oil bath increased to 150° C. After 48 hours the reaction mixture was cooled to room temperature, then diluted with ethyl acetate and filtered. The filtrate was concentrated and the resulting solid was taken up in ethyl acetate (5 mL) and sonicated. Filtration gave 0.54 g (34%) of 4-(3,4-dioxo-2-ethoxy-cyclobut-1-enylamino)-3-ethylbenzonitrile as a light brown solid: 1H NMR (DMSO-d6): δ 10.56 (br s, 1H), 7.70 (br s overlapping a doublet at δ 7.69, 2H), 7.30 (d, 1H), 4.71 (q, 2H), 2.74 (q, 2H), 1.37 (t, 3H), 1.15 (t, 3H).

Provenance & Evidence