Ethyl 3-(2,4-dichlorophenyl)-3-oxopropanoate → Ethyl 2-amino-4-(4-chlorophenyl)thiazole-5-carboxylate

関与物質

反応手順

To a cold (5° C.) vigorously stirred mixture of 121.87 g (0.936 mole) of ethyl acetoacetate, 314 ml. of benzene and 626 ml. of water was added 41.25 ml. of 33% sodium hydroxide. To the above mixture was added simultaneously in two dropping funnels 177.0 g (1.01 mole) of p-chlorobenzoyl chloride and 188.8 ml. of 33% sodium hydroxide in 2 hours. The reaction mixture became pasty. The reaction mixture was heated at 35° C. for 1 hour, cooled and filtered to give 170.0 g of sodium salt of ethyl 2-benzoylacetoacetate. Part (150 g) of this salt was added to a mixture of 39.0 g (0.729 mole) of ammonium chloride and 78 ml. of concentrated ammonium hydroxide in 780 ml. of water. The mixture was stirred at 40°-50° C. for 3 hours and cooled in an ice bath. The precipitate was filtered to give 115.5 g of yellow solid which was Kugelrohr distilled to give 76.0 g (38% based on ethyl acetoacetate) of crude ethyl p-chlorobenzoylacetate. A mixture of 40.0 g (0.175 mole) of crude ethyl p-chlorobenzoylacetate, 24.2 g (0.18 mole) of sulfuryl chloride and some chloroform was held at reflux for 6 hours, cooled and concentrated to give 49.0 g of crude ethyl 2-chloro-p-chlorobenzoylacetate. A mixture of 46.0 g (0.174 mole) of crude ethyl 2-chloro-p-chlorobenzoylacetate, 13.25 g (0.174 mole) of thiourea, and 174 ml. of ethanol was held at reflux for 2 hours and cooled. The precipitate was filtered and neutralized with saturated sodium bicarbonate. The insoluble material was filtered to give 37.0 g (80%) of ethyl 2-amino-4-p-chlorophenyl-5-thiazolecarboxylate, m.p. 198°-200° C. To a cold (-5° C.) mixture of 11.3 g (0.04 mole) of ethyl 2-amino-4-p-chlorophenyl-5-thiazolecarboxylate and 80 ml. of 85% phosphonic acid was added 40 ml. of 70% nitric acid. To the above mixture was added with vigorous stirring, 4.0 g (0.0434 mole) of sodium nitrite in 20 minutes at -5°-0° C. The reaction mixture was stirred at -5°-0° C. for 10 minutes and poured into a mixture of 4.0 g (0.04 mole) of cuprous chloride, 20 ml. of concentrated hydrochloric acid and 20 ml. of water. The reaction mixture was stirred at room temperature for 30 minutes, after which time evolution had subsided. The precipitate was filtered to give 10.5 g of solid which was Kugelrohr distilled (145° C. at 0.05 mm Hg) to give 6.0 g of solid, m.p. 113°-120° C., which was recrystallized from hot ethanol to give 4.4 g (37%) of ethyl 2-chloro-4-p-chlorophenyl-5-thiazolecarboxylate as a white solid, m.p. 119°-120° C.

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