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ChemicalBook CAS DataBase List 3-(Trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine hydrochloride
762240-92-6

3-(Trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine hydrochloride synthesis

3synthesis methods
A suspension of N'-[(2Z)-Piperazin-2-ylidene]trifluoroacetohydrazide (27.3 g, 0.13 mol) in 110 mL of methanol was WARMED TO 55 ℃. 37% Hydrochloric acid (11.2 mL, 0.14 mol) was added over 15 min at this temperature. During the addition, all solids dissolved, resulting in a clear solution. The reaction was aged for 30 min. The solution was cooled to 20 ℃ and aged at this temperature until a seed bed formed (10 min to 1 h). 300 ML of MTBE was charged at 20 ℃ over 1 h. The resulting slurry was cooled to 2 ℃, aged for 30 min and filtered. Solids were washed with 50 mL of ethanol: MTBE (1: 3) and dried under vacuum at 45 ℃. Yield of 3-(Trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine hydrochloride was 26.7 g (99.5 area wt% pure by HPLC).
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Yield:762240-92-6 92.6%

Reaction Conditions:

with hydrogenchloride in ethanol;water at 50 - 54; for 3.5 h;Temperature;

Steps:

2-5

Take 52.54g (0.25mol) of the intermediate N-[(2Z)-piperazin-2-ylidene]trifluoroacethydrazine obtained above, add 600ml of ethanol, and stir until uniform.Drop 27.88g (0.28mol) of 36% hydrochloric acid, and heat to 50-54°C,Incubate the reaction for 3.5 hours to form a ring and form a salt. After the reaction is over,Slowly lower the temperature to 0-5 to charge the analytical crystal, filter by suction, and dry the wet product,Obtain the target product sitagliptin intermediate 3-trifluoromethyl-5,6,7,8-tetrahydro-1,2,4-triazole[4,3-a]pyrazine hydrochloride 52.92g, The yield is 92.6%, the purity is greater than or equal to 99.4%, and the content is greater than or equal to 98.7%

References:

CN112358484,2021,A Location in patent:Paragraph 0024; 0030; 0034-0035; 0039-0040; 0044-0045; 0049

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