Sodium Hydroxide → 1-Methyl-1h-pyrazole-4-sulfonic acid {2-[3'-(4-methoxymethyl-phenyl)-2,3,5,6-tetrahydro-[1,2']bipyrazinyl-4-yl]-ethyl}-methyl-amide hydrochloride

Participants

Reaction Conditions

Reaction Steps

Cool a suspension of 3′-(4-methyoxymethyl-phenyl)-3,4,5,6-tetrahydro-2H-[1,2′]bipyrazinyl dihydrochloride (23.62 g, 66.11 mmol) in 1,2-dichloroethane (500 mL) at 5° C. Treat with 1.0 M NaOH (141 mL, 141 mmol), separate layers, dry the organics over Na2SO4, filter, then add to a solution of 1-methyl-1H-pyrazole-4-sulfonic acid methyl-(2-oxo-ethyl)-amide (17.66 g, 81.29 mmol) in 1,2-dichloroethane (1 L). Cool the reaction mixture to 5-10° C., treat with sodium triacetoxyborohydride (29.50 g, 132.2 mmol), and stir at room temperature overnight. Recool the reaction to 5° C., treat with 5 M NaOH (200 mL), and separate the resulting layers. Extract the aqueous layer with CH2Cl2 (500 mL), combine the organics, dry over Na2SO4, filter and concentrate. Dissolve the crude material in MeOH/EtOAc, treat with activated carbon (50 g) at room temperature for 1 hr., then filter through celite and concentrate to provide the free base of the title compound as an oil (29.8 g, 93%). Cool anhydrous EtOH (100 mL) to 5° C. and then add dropwise acetyl chloride (4.45 mL, 61.39 mmol). Stir the resulting solution at room temperature for about 15 min., then add it dropwise to a solution of the above free base dissolved in anhydrous EtOH (800 mL). Stir at room temperature for 0.5 hr., then concentrate in vacuo to ca. 20% of the original volume. Treat the resulting oil/solid with EtOAc (1.5 L). Recover the resulting yellow solid by vacuum filtration and dry in vacuo to provide the title compound (27.28 g, 85.2%). MS ES: m/z=486 [M+H]+.

Provenance & Evidence