Sodium Hydroxide → 6,7-Dihydro-4-methyl-2-(4-chlorophenyl)-4H-pyrano[4,3-d]thiazole-4-acetic acid

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Reaction Steps

The latter ester is dissolved in methanol (500 ml) followed by the addition of sodium hydroxide (80 g) and the resulting mixture is heated at reflux temperature for 5 hr. The solvent is removed by distillation, water is added to the residue and the solution is extracted with ether. The aqueous basic phase is mixed with ether and the mixture is acidified with dilute hydrochloric acid. The organic phase is separated, washed with saturated sodium chloride solution, dried over sodium sulfate, and evaporated under reduced pressure. The residue is crystallized from chloroform-ether to give the title compound; mp 162°-164° C., γmaxCHCl3 2900 and 1705 cm-1.

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