Hydrochloric Acid → Ethyl 2-Chloro-4-Ethyl-5-Thiazolecarboxylate

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Reaction Steps

Ethyl 2-chloro 3-oxo-pentanoate is prepared from ethyl 3-oxo-pentanoate and sulfuryl chloride utilizing the procedure of Bankowski et al, Rocz. Chem., Volume 49, Page 1899 (1971). A mixture of 9.2 g (0.0515 mole) of ethyl 2-chloro 3-oxo-pentanoate, 3.92 g (0.0515 mole) of thiourea and 30 ml. of ethanol was held at reflux for 17 hours. Ethanol was removed under reduced pressure and the residue was treated with 300 ml. of saturated sodium bicarbonate solution. The solid precipitate was collected to give 11.2 g of white solid, m.p. 165°-170° C. which was recrystallized from ethanol to give 7.7 g (75%) of ethyl 2-amino-4-ethyl-5-thiazolecarboxylate as colorless prisms, m.p. 177°-179° C. To a solution of 7.0 g (0.0349 mole) of ethyl 2-amino-4-ethyl-5-thiazolecarboxylate and 0.2 g of CaSO 4 in 60 ml. of concentrated HCl was added dropwise a solution of NaNO2 in 20 ml. of water in such a way that the reaction temperature did not exceed 30° C. The reaction mixture was stirred for 30 minutes and poured into a solution of 3.5 g (0.035 mole) of cuprous chloride in 30 ml. of 6N HCl. The resulting dark blue solution was stirred for 30 minutes and extracted with ether. The ether solution was dried and concentrated under reduced pressure. The residue was Kugelrohr distilled at 2 mm. to give 4.35 g of yellow liquid which was chromatographed on silica gel to give 4.0 g (52%) of the desired product as colorless liquid, nD25 =1.5189.

Provenance & Evidence