Dabigatran etexilate intermediate synthesis method
A compound, haloformate technology, applied in the field of chemistry, can solve the problems of long reaction steps, low total yield of intermediates, and large amount of waste acid
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Embodiment 1
[0069] Preparation of 2-chloromethyl-1-methyl-1H-benzimidazole-5-carboxylic acid:
[0070] Take 11 g of 3-amino-4-methylaminobenzoic acid, add 200 ml of ethyl acetate, stir well, then add dropwise the solution obtained by dissolving 12 g of chloroacetic anhydride in 52 g of ethyl acetate. The addition was completed in about 10 minutes. After the addition, it was reacted at room temperature for 30 minutes, and then heated to 65°C for 4 hours. TLC (developer: methanol: dichloromethane = 5:1) determined the end point of the reaction. After the reaction was completed, cool to room temperature, filter, wash the reaction flask and filter cake with 50ml ethyl acetate, and dry under reduced pressure at 65°C to obtain the target compound product with a yield of 91.5%.
Embodiment 2
[0072] Preparation of 2-chloromethyl-1-methyl-1H-benzimidazole-5-carboxylic acid:
[0073] Take 11g of 3-amino-4-methylaminobenzoic acid, add 200ml of ethyl acetate, stir well, add 20g of chloroacetic acid, heat up to 40°C and react for 8 hours, TLC (developing agent methanol:dichloromethane=5:1) to determine end point of the reaction. After the reaction was completed, cool to room temperature, filter, wash the reaction flask and filter cake with 50ml of ethyl acetate, and dry under reduced pressure at 65°C to obtain the target compound product with a yield of 78.6%.
Embodiment 3
[0075] Preparation of ethyl 2-chloromethyl-1-methyl-1H-benzimidazole-5-carboxylate:
[0076] Take 11.2g of the product obtained in Example 1 or 2, add 180ml of absolute ethanol, stir well, add 14.3g of thionyl chloride dropwise under cooling in an ice-water bath, and finish adding in about 10 minutes. After the addition, react in an ice-water bath for 30 minutes, and then heat up After reflux for 6 hours, TLC (developing solvent: dichloromethane: methanol = 10:1) determined the end point of the reaction. After the reaction is complete, add 2g of activated carbon, stir and decolorize for 0.5-1 hour, filter while hot, concentrate to dryness under reduced pressure, add 40ml of ethanol to reflux to dissolve, add 20mlg of ethyl acetate, cool and crystallize, filter after cooling in an ice-water bath, and store at 50°C Dry under reduced pressure to obtain the target compound product with a yield of 93.4%.
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