Sodium → Ethyl 4-(3-(tert-butylamino)-2-methylquinoxalin-5-yl)-2,4-dioxobutanoate

Participants

Reaction Conditions

Reaction Steps

To a 25-mL round-bottomed flask was added EtOH (4 mL) and sodium ethoxyde (1.01 g of 21% in EtOH, 3.11 mmol). The reaction mixture was cooled to −10° C. and added ethyl oxalate (0.21 mL, 1.55 mmol, Sigma-Aldrich) and 1-(3-(tert-butylamino)-2-methylquinoxalin-5-yl)ethanone (606a) (0.4 g, 1.55 mmol) slowly. The reaction mixture was warmed to RT and stirred at RT for 18 h. The reaction mixture was diluted with water (10 mL) and partially concentrated under vacuum. The reaction mixture was diluted with HCl (1 N, 5 mL) and extracted with EtOAc (15 mL). The organic extract was washed with brine (10 mL), dried over Na2SO4, and concentrated. The crude material was absorbed onto a plug of silica gel and purified by chromatography through a Redi-Sep pre-packed silica gel column (12 g), eluting with a gradient of 10% to 30% EtOAc in hexanes to give ethyl 4-(3-(tert-butylamino)-2-methylquinoxalin-5-yl)-2,4-dioxobutanoate as an orange oil (135 mg, 24% yield). m/z (ESI, +ve) 358.1 (M+H)+. To a 15-mL glass tube was added ethyl 4-(3-(tert-butylamino)-2-methylquinoxalin-5-yl)-2,4-dioxobutanoate (135 mg, 0.38 mmol), hydrazine (12 μL, 0.38 mmol), and AcOH (2 mL). The tube was sealed and heated at 85° C. for 1 h. The reaction mixture was cooled to RT and the solvent was removed under vacuum. The mixture was diluted with EtOAc (10 mL) and NaOH (1 N, 5 mL). The organic extract was washed with water (5 mL), dried over Na2SO4, and concentrated. The crude material was absorbed onto a plug of silica gel and purified by chromatography through a Redi-Sep pre-packed silica gel column (12 g), eluting with a gradient of 30% to 40% EtOAc in hexanes to give ethyl 5-(3-(tert-butylamino)-2-methylquinoxalin-5-yl)-1H-pyrazole-3-carboxylate (467a) (102 mg, 76% yield) as a white solid. 1H NMR (400 MHz, DMSO-d6) δ 7.82-7.97 (m, 1H), 7.74 (d, J=7.82 Hz, 1H), 7.51-7.60 (m, 1H), 7.40 (t, J=8.90 Hz, 1H), 6.00-6.07 (m, 1H), 4.31 (q, J=7.11 Hz, 2H), 2.56 (s, 3H), 1.53 (s, 9H), 1.33 (t, J=7.14 Hz, 3H). m/z (ESI, +ve) 354.0 (M+H)+.

Provenance & Evidence