Ammonium Chloride → 2-(2-Cyano-3-methylamino-4-nitrophenyl)-2-methyl-3-oxobutyric acid ethyl ester

Participants

Reaction Steps

To a 1 L two-neck round bottom flask equipped with a magnetic stir bar and internal thermometer was added potassium tert-butoxide (5.0 g, 45 mmol) and dimethylsulfoxide (100 mL). To the rapidly stirred suspension was added 2-methylacetoacetate (7.13 g, 49.5 mmol) dropwise over 5 minutes. After the addition was complete the mixture was clear and slightly yellow. To the reaction mixture was then added 6-chloro-2-methylamino-3-nitro-benzonitrile (8.6 g, 41 mmol) from Step 1 in portions over 15 minutes. The reaction mixture immediately became deep red in color and the temperature rose to 40° C. The reaction mixture was stirred for 1.5 hours, then poured into a saturated solution of NH4Cl (100 mL). The mixture was extracted with EtOAc (3×150 mL). The organic layers were combined and washed with brine (3×100 mL). The organic layer was dried over sodium sulfate, filtered, and concentrated under vacuum to produce a deep red oil. Methanol (40 mL) was added and the mixture was stirred for 1.5 hours with cooling over an ice bath. The resulting precipitate was recovered by filtration and washed with cold methanol to provide 2-(2-cyano-3-methylamino-4-nitro-phenyl)-2-methyl-3-oxo-butyric acid ethyl ester (7.13 g, 40.6%) as a yellow solid, which was used without further purification. 1H NMR (400 MHz, DMSO-d6) δ 8.23 (d, 1H, J=9.0 Hz), 8.10-8.05 (m, 1H), 6.64 (d, 1H, J=9.0 Hz), 4.28-4.19 (m, 2H), 3.17 (d, 3H, J=5.5 Hz), 2.36 (s, 3H), 1.81 (s, 3H), 1.22 (t, 3H, J=7.0 Hz).

Provenance & Evidence