The esterification of 4-hydroxyphenylacetic acid (I) with isopropanol and H2SO4 gives the corresponding isopropyl ester (II), which is then cyclocondensed with 1-isobutoxy-2-chloroethyl isothiocyanate (III) by means of K2CO3 in acetone yielding isopropyl 2-[4-(4-isobutoxy-2-thiazolin-2-yloxy) phenyl]acetate (IV). Elimination of isobutanol from (IV) by means of p-toluenesulfonic acid in hot DMF affords isopropyl 2-[4-(2-thiazolyloxy)phenyl] acetate (V), which is methylated with methyl bromide and KOH in DMF giving isopropyl 2-[4-(2-thiazo)yloxy)phenyl]propionate (VI). Finally, this compound is hydrolyzed with NaOH in aqueous methanol.
The condensation of 2-chlorothiazole (VII) with isopropyl 2-(4-hydroxyphenyl)propionate (VIII) by means of K2CO3 in DMF at 150 C gives (VI), previously obtained.