2,4-Dimethylbenzylamine → 3-tert-Butylamino-4-(2,4-dimethyl-benzylamino)-cyclobut-3-ene-1,2-dione

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A solution of 3-butoxy-4-tert-butylamino-cyclobut-3-ene-1,2-dione (1.13 g, 5.0 mmol, Example 1) and 2,4-dimethylbenzylamine (0.68 g, 5.0 mmol, a mixture of 2,4- and 2,6-dimethylbenzylamine isomers) in tetrahydrofuran (10 mL) was stirred at room temperature for approximately 16 hours. Removal of solvent, thorough trituration of the residue with diethyl ether and drying provided 1.07 g of crude product. Three recrystallizations of this material from acetonitrile gave 0.67 g (47%) of the title compound as a white solid: mp 228°-229° C.; 1H NMR (DMSO-d6) δ7.57 (m, 1H), 7.48 (s, br, 1H), 7.17 (d, 1H), 7.03 (s, br, 1H), 7.00 (d, br, 1H), 4.69 (d, 2H), 2.27 (s, 3H), 2.24 (s, 3H), 1.35 (s, 9H) ppm. IR (KBr): 3310, 1785, 1670 cm-1 ; MS (m/z) 286 (M+). HPLC indicates a major component (98.7%).

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