Pyrazine-2-Carboxylic Acid Hydrazide → 7-[(2,4-Dichloro-3-fluorophenyl)carbonyl]-3-(2-pyrazinyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine

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To a solution of 4-[(2,4-dichloro-3-fluorophenyl)carbonyl]-2-piperazinone (I37) (0.146 g, 0.5 mmol) in Dichloromethane (DCM) (3 mL) was added triethyloxonium tetrafluoroborate (0.100 g, 0.525 mmol). The solution was then stirred, under argon, for 10 minutes before 2-pyrazinecarbohydrazide (commercially available from e.g. TimTec, J& W PharmLab and Akos Consulting, 0.083 g, 0.600 mmol) was added. The solution was then stirred for a further hour before the solvent was concentrated and n-butanol (3.00 mL) was added. The solution was then stirred, under argon and reflux, for 3 hours before being cooled to room temperature. The solvent was then evaporated in vacuo and the remaining residue was purified by flash chromatography (Biotage SP4, 25M cartridge) with a gradient of 0-10% 2M NH3/MeOH in DCM. TLC confirmed product location and the solvent from the combined fractions was evaporated in vacuo. The remaining residue was then further purified by mass-direct automated HPLC, before the solvent was again evaporated in vacuo. The remaining solid was then triturated in ether before being dried in a vac-oven to yield the product in 0.056 g.

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