Phosphorus oxychloride → Ethyl 4-chloro-7-methyl-1,8-naphthyridine-3-carboxylate

Participants

Reaction Steps

3-Carbethoxy-4-hydroxy-7-methyl-1,8-naphthyridine (3.8 g; 0.016 M) was suspended in POCl3 (46 ml; 0.45 M) and the mixture heated at 70°-80° C. for 4 hr. The solution was concentrated in vacuo and the residue poured carefully onto crushed ice. The resulting solution was basified with 10% aq. NaOH to pH 6 and extracted with Et2O. The Et2O extracts were combined, washed with saturated brine and dried over anhydrous MgSO4. The drying agent was removed by filtration and the filtrate was decolourised by refluxing with charcoal, filtered through Kieselguhr and evaporated to dryness in vacuo to yield the product, 3.7 g. (92%), m.p. 92°-93° C. (dec.). An analytical sample was obtained by chromatography over silica gel using CHCl3 /MeOH (9:1) as eluent. m.p. 90°-91° C. (dec.) (Found: N, 11.36; C, 57.80; H, 4.66; Cl, 14.13%. C12H11ClN2O2 requires: N, 11.18; C, 57.48; H, 4.39; Cl, 14.17%), νmax (KBr) 1720, 1600, 1580, 1470, 1260, 1213, 1170, 1022, 810 cm-1, δ [(CD3)2SO] 1.39 (t), 4.4 (q), (CH3CH2), 2.74 (s) (CH3), 7.69 (d), 8.6 (d), 9.21 (s) (heterocyclic protons), m/e 250 (M+ ; 100%), 222 (41%).

Provenance & Evidence