| 摘要 |
<p>2-(2-aryl benzoxazol-5-yl) propionic acids are prepd. by (a) condensing 3-amino 4-hydroxy acetophenone with an acid chloride of formula (II), in presence of a base such as triethylamine, at below 5 deg.C; after addn. is complete, the mixt. is heated on a water bath at 30 deg.C for 0.5-3 hr., the solvent removed in vacuum and the anilide heated in inert atmos. at 180-240 deg.C in a solvent, for cyclisation to a benzoxazole of formula (III), which is purified by sublimation or crystallisation, (b) reductive carboxylation of (III) by treatment with 5-toluene sulphonyl isocyanate to give benzoxazolyl propionic acids of formula (I), in which R is H, 4-chloro, 3-methoxy or other gp.</p> |
