Ethanol → Ethyl 2-(2-thioxo-2,3-dihydrobenzoxazol-5-yl)propionate

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Reaction Steps

2-[2-(4-methoxyanilino)-6-benzoxazolyl]propionitrile (i) A stirred mixture of ethyl 2-(3-amino-4-hydroxyphenyl)propionate (8.4 g.), potassium ethylxanthate (6.33 g.), ethanol (38 ml.) and water (6.5 ml.) was heated under reflux for 4 hours. The solution was evaporated to half volume and diluted with water (65 ml.). The mixture was acidified with 2N-hydrochloric acid and extracted several times with ether. The ethereal solution was washed with water, then dried with anhydrous sodium sulphate, and evaporated to give ethyl 2-(2-thioxo-2,3-dihydrobenzoxazol-5-yl)propionate as an oil. Dry chlorine was passed into a solution of the thione (9 g.) in freshly dried and distilled chloroform (150 ml.) with stirring for 4 hours. The solution was then washed with water, N-sodium hydroxide solution, then water (3x). The dried (Na2SO4) organic solution was evaporated to yield ethyl 2-(2-chloro-5-benzoxazolyl]propionate as a brown oil which was shown to be a single compound by thin layer chromatography. (j) A mixture of the 2-chloro compound (12.5 g.) of Example 3 (i) and p-chloroaniline (25 g.) was heated on a steam bath for one hour. The reaction mixture was dissolved in chloroform and the solution was washed with 2N hydrochloric acid (2x), water, 2N sodium hydroxide solution (2x) and water (3x). The chloroform solution was stirred with charcoal and anhydrous sodium sulphate, then filtered and evaporated. The residue was purified using prep t.l.c. plates to give ethyl-2-[2-(4-chloroanilino) -5-benzoxazolyl]propionate, mpt 135°-7° C., which was characterised by ir uv and nmr spectroscopy and by micro analysis which gave C 62.45% H 5.11% N 7.97% C18H17ClN3O2 requires C 62.70% H 4.93% N 8.13%

Provenance & Evidence