Lithium Hydroxide → 2-(2-o-Tolyl-chroman-6-yloxy)-thiazole-5-carboxylic acid lithium salt

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Reaction Steps

To a solution of 2-(2-o-tolyl-chroman-6-yloxy)-thiazole-5-carboxylic acid methyl ester (300 mg, 0.8 mmol) in tetrahydrofuran (5.5 ml) and methanol (1.0 ml) at room temperature a solution of lithium hydroxide (18.9 mg, 1.0 eq) in water (1.0 ml) was added and the mixture stirred for 3 h. The solvent was removed under reduced pressure and the resulting residue dissolved in water and lyophilized. The obtained white 2-(2-o-tolyl-chroman-6-yloxy)-thiazole-5-carboxylic acid lithium salt (100% yield) was used in the formation of 2-(2-o-tolyl-chroman-6-yloxy)-thiazole-5-carboxylic acid amides without further purification. For the preparation of the free acid, the crude lithium salt was dissolved in water and the resulting solution acidified with aqueous hydrochloric acid. The resulting suspension was filtered and the precipitate washed with water. The obtained 2-(2-o-tolyl-chroman-6-yloxy)-thiazole-5-carboxylic acid was dried under reduced pressure. It can be used in the next step without further purification as described for the lithium salt.

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