Hydrochloric Acid → Ethyl 5,7-diethyl-4-hydroxy-2-oxo-1,2-dihydro-1,6-naphthyridine-3-carboxylate

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Reaction Steps

Diethylamine (0.63 ml) was added dropwise to a stirred solution of trimethylaluminium (2M solution in toluene; 3 ml) in dichloromethane (5 ml) under an atmosphere of argon. The mixture was stirred for 30 minutes then a solution of ethyl 5,7-diethyl-2-oxo-1,2-dihydro-1,6-naphthyridine-3-carboxylate (548 mg) in dichloromethane (5 ml) was added dropwise. The resulting mixture was heated at reflux for 4 hours then cooled in ice. A mixture of 2M hydrochloric acid (1 ml) and methanol (1 ml) was added dropwise. The mixture was filtered and the filtrate was concentrated by evaporation to give a brown oil which was purified by flash chromatography, eluting with methanol/ethyl acetate (1:24 v/v), to give 5,7-diethyl-2-oxo-1,2-dihydro-1,6-naphthyridine-3-N,N-diethylcarboxamide (B) (391 mg) as a solid, m.p. 56°-59° C.; NMR (CDCl3): 1.17(t, 3H), 1.25-1.4(complex m, 9H), 2.85(q, 2H), 3.07(q, 2 H), 3.32(q, 2H), 3.63(q, 2H), 6.95(s, 1H), 8.08(s, 1H), 12.28(s, 1H); mass spectrum (CI, ammonia): 302 (M+H)+ ; microanalysis, found C, 66.4; H, 7.6; N, 13.6%; C17H23N3O2.0.25H2O requires: C, 66.7; H, 7.7; N, 13.7%.

Provenance & Evidence