Suspend 3′-(4-methanesulfonylphenyl)-3,4,5,6-tetrahydro-2H-[1,2′]bipyrazinyl (0.191 g, 0.60 mmol) in tetrahydrofuran (4 mL). Add 1,3,5-trimethyl-1H-pyrazole-4-carbaldehyde (0.087 g, 0.63 mmol) in tetrahydrofuran (435 μL), then sodium triacetoxyborohydride (0.13 g, 0.63 mmol). Subject reaction to ultrasound for 30 sec. then stir under nitrogen at room temperature for 7 hr. Add saturated aqueous sodium hydrogen carbonate (10 mL) followed by 2 N sodium hydroxide (1 mL) to the mixture and extract with DCM (3×20 mL). Pass the combined DCM extracts through an IST Phase Separator Frit®, concentrate and purify (silica gel chromatography, eluting with 0:100 to 12:88 methanol:DCM), to give the title compound (241.9 mg, 91%). MS (ES): m/z=441.2 [M+H]+.
