Triethylamine → 3'-chloro-4-(1-ethyl-5-methyl-1H-pyrazol-4-ylmethyl)-3,4,5,6-tetrahydro-2H-[1,2']bipyrazinyl

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Reaction Steps

Dissolve 1-ethyl-5-methyl-1H-pyrazole-4-carbaldehyde (2.92 g, 21.1 mmol) in 1,2-dichloroethane (184 mL). Add 3′-chloro-3,4,5,6-tetrahydro-2H-[1,2′]bipyrazinyl dihydrochloride (4.97 g, 18.3 mmol), triethylamine (5.9 mL, 42.3 mmol), sodium triacetoxyborohydride (6.72 g, 31.7 mmol) and acetic acid (1.98 mL) and stir at room temperature for 18 hr. Add aq. saturated sodium bicarbonate and extract four times with DCM. Dry combined organic layers (magnesium sulfate), filter, concentrate, and purify (silica gel chromatography, eluting with 50:50 to 100:0 ethyl acetate:hexanes then 10:90 to 20:80 methanol:ethyl acetate) to give 3′-chloro-4-(1-ethyl-5-methyl-1H-pyrazol-4-ylmethyl)-3,4,5,6-tetrahydro-2H-[1,2′]bipyrazinyl (5.2 g, 88%). MS (ES): m/z=321 [M+H]+.

Provenance & Evidence