Ethyl orthoformate → 2-(6-Benzyloxy-benzoimidazol-1-yl)-4-(3-chloro-phenyl)-thiazole-5-carboxylic acid ethyl ester

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Reaction Steps

A mixture of the 2-(2-amino-5-benzyloxy-phenylamino)-4-(3-chloro-phenyl)-thiazole-5-carboxylic acid ethyl ester (VII.25) from previous step, 50 mL of acetic acid, 5 mL of triethyl orthoformate was heated to 50 degrees for 1 hour. The mixture was concentrated under reduced pressure and the residue taken up in 200 mL of dichloromethane. The mixture was washed with 100 mL saturated sodium bicarbonate. The aqueous layer was extracted twice with 100 mL of dichloromethane. The combined organic layers were washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The residue was triturated with diethyl ether to afford 3.5 g of 2-(6-benzyloxy-benzoimidazol-1-yl)-4-(3-chloro-phenyl)-thiazole-5-carboxylic acid ethyl ester (I.25a) as an off-white solid.

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