(R)-3,3-Dimethyl-2-aminobutane → (+)-(R)-4-[3,4-dioxo-2-(1,2,2-trimethyl-propylamino)-cyclobut-1-enylamino]-3-ethylbenzonitrile

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Reaction Steps

4-(2-ethoxy-3,4-dioxo-cyclobut-1-enylamino)-3-ethylbenzonitrile (1.26 g, 4.66 mmol) and a solution of (R)-1,2,2-trimethylpropylamine (9.3 mmol) in ethanol (58 mL) were stirred at room temperature for 24 hours. The resulting yellow solution was concentrated to a yellow oil, which was dissolved in acetonitrile (20 mL) and stirred at room temperature. The yellow solid which precipitated was filtered off and rinsed with ethyl acetate to yield 0.79 g (52%) of (+)-(R)-4-[3,4-dioxo-2-(1,2,2-trimethyl-propylamino)-cyclobut-1-enylamino]-3-ethylbenzonitrile as an off-white solid: mp 235°-237° C.; [α]D25 =+68.20° (DMSO, c 0.0072); 1H NMR (DMSO-d6): δ 8.04 (br s, 1H), 8.04 (d, 1H), 7.69-7.57 (m, 3H), 4.05 (m, 1H), 2.71 (q, 2H), 1.27-1.16 (overlapping doublet and triplet, 6H), 0.91 (s, 9H). IR (KBr): 3278, 2959, 2222, 1793, 1674, 1598, 1576, 1522 cm-1 ; MS (m/z) 325 (M+).

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