Diethyl squarate → HCID 54525291, compound

Participants

Reaction Steps

A solution of 3,4-diethoxy-3-cyclobutene-1,2-dione (10 g, 59 mmol) and (R)-2-amino-3,3-dimethylbutane (353 mL of a 0.2M solution in absolute ethanol, 71 mmol) was stirred at room temperature for 24 hours. Another portion of (R)-2-amino-3,3-dimethylbutane (150 mL of a 0.2M solution in absolute ethanol, 30 mmol) was added and the resulting solution was stirred at room temperature for 24 hours. The slurry was filtered, and the filtrate concentrated under reduced pressure. The resulting solid was trituated with hexane:ethyl acetate (150:5 mL), then washed with hexane to give 9.78 g (74%) of (R)-3-ethoxy-4-(1,2,2-trimethyl-propylamino)-cyclobut-3-ene-1,2-dione as a white solid: 1H NMR: (DMSO-d6): δ 8.72 and 8.50 (two d, 1H, rotamers), 4.65 (m, 2H), 3.90 and 3.42 (two m, 1H, rotamers), 1.37 and 1.35 (two overlapping t, 3H, rotamers), 1.10 (two overlapping d, 3H, rotamers), 0.85 and 0.84 (two s, 9H, rotamers) ppm. IR (KBr): 3150, 2950, 1800, 1700 cm-1 ; MS (m/z): 225 (M+).

Provenance & Evidence