Olmesartan Impurity 9 synthesis

Yield:849206-42-4 97%

Reaction Conditions:

with dicyclohexyl-carbodiimide in acetone at 20; for 48 h;

Steps:

11

33,0 grams of dicyclohexylcarbodiimide (DCC) was added into a suspension of 30.0 grams of 4- (1-hydroxy-1-methylethyl)-2-propyl-imlidazole -5-carboxylic acid (formula III) in 300 ml of acetone. The reaction was performed at ambient temperature for 48 hours. The mixture was suction filtered and washed. The filtrate was concentrated and acetone was recovered. 120 ml of ethyl acetate and 120 ml of water were added into the residual liquid, and pH was adjusted to 2~3 with concentrated hydrochloric acid. The aqueous layer was separated and the organic layer was further extracted with 20 ml x 2 of water. 150 ml of ethyl acetate was added into the combined aqueous portion and pH was adjusted to 10 with 30% sodium hydroxide solution. Salt was added to be saturated and the organic layer was separated. The aqueous layer was further extracted with 30 ml x 2 of ethyl acetate. Combined organic portion was dried over anhydrous magnesium sulfate and filtered, the solvent was evaporated to give 35,3 grams of 4,4-dimethyl-2-propyl-4,6-dihydrofuro[3,4-d]imidazole (formula II), resulting in a yield of 97%.

References:

EP2374799,2011,A1 Location in patent:Page/Page column 11