Ammonia → Ethyl 4-chloro-6-ethoxy-7-methyl-1,8-naphthyridine-3-carboxylate

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Reaction Steps

Ethyl 6-ethoxy-4-hydroxy-7-methyl-1,8-naphthyridine-3-carboxylate (2.5 g) was added to phosphorus oxychloride (20 ml) with stirring at ambient temperature. The mixture was warmed to 40° C. and kept at this temperature for 1 hour then cooled to 10° C. The mixture was added to excess ice/water and the mixture basified with aqueous ammonia solution (specific gravity 0.88) while keeping the temperature below 5° C. The product was extracted into dichloromethane. The combined dichloromethane extracts were evaporated under reduced pressure at ambient temperature to give ethyl 4-chloro-6-ethoxy-7-methyl-1,8-naphthyridine-3-carboxylate, m.p. >250° C.

Provenance & Evidence