2-Hydrazinoquinoxaline → 3-Oxo-2-quinoxalin-2-yl-1,2,3,4,6,7-hexahydro-pyrazolo[4,3-c]pyridine-5-carboxylic acid tert-butyl ester

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Reaction Steps

To a solution of 4-oxo-piperidine-1,3-dicarboxylic acid 1-tert-butyl ester 3-ethyl ester (500 mg, 1.84 mmol; Tetrahedron 1994, 50, 515) in toluene (10 mL) was added quinoxalin-2-yl-hydrazine (295 mg, 1.85 mmol; Heterocycles 1985, 23, 2603). This mixture was stirred at reflux overnight, cooled to room temperature, concentrated, and purified by flash column chromatography (25→75% ethyl acetate/hexanes) to give 600 mg (89%) of the title compound of Example 75, Step A as a light orange solid. 1H NMR (CDCl3, 250 MHz, 5:1 mixture of tautomers) δ 11.94 (br s, 0.83H), 10.16 (s, 0.17H), 9.57 (s, 0.83H), 8.13 (dd, 1H), 7.91-7.69 (c, 3H), 4.45 (s, 1.66H), 4.33 (s, 0.34H), 3.79-3.72 (c, 2H), 2.82-2.72 (c, 2H), 1.52 (s, 9H); MS (APCI) 368 (MH+).

Provenance & Evidence