A mixture of 2-chlorothiazole (5.0 g), ethyl 2-(4-hydroxyphenyl)propionate
(8.1 g), potassium carbonate powder (8.65 g) and dimethylformamide (80 ml)
is stirred at 150°-155°C for 2.5 hours. The solvent is distilled out under
reduced pressure. To the residue is added water and extracted with ether. The
extract is washed with a 10% aqueous solution of sodium hydroxide and
water and dried. The ether is evaporated. The residue is subjected to
chromatography using silica gel and eluted with 50% benzene-hexane,
benzene and 10% ether-benzene to yield ethyl 2-[4-(2-thiazolyloxy)-
phenyl]propionate (5.8 g).
The product is dissolved in a mixture of a 20% aqueous solution of potassium
hydroxide (30 ml) and 95% ethanol (30 ml). The solution is kept at room
temperature for 30 minutes. The solvent is evaporated. The residue is
acidified with hydrochloric acid after addition of water, and extracted with
ether. The extract is washed with water and dried over magnesium sulfate.
The solvent is distilled out. The residue is recrystallized from ether-hexane to
give 2-[4-(2-thiazolyloxy)phenyl]propionic acid (4.8 g).
The product (5.0 g) is dissolved in an aqueous solution (30 ml) of sodium
hydroxide (0.82 g). To the solution washed with ether is added an aqueous
solution (5 ml) of calcium chloride 2 hydrate (1.6 g) to form a precipitate. The
precipitate washed with water gives calcium 2-[4-(2-thiazolyloxy)phenyl]propionate (5.5 g) melting at 143°-145°C.
