2-CHLORO-3-(PIPERAZINYL)PYRAZINE

Synthesis

The general procedure for the synthesis of 2-chloro-3-piperazinopyrazine from tert-butyl 4-(3-chloropyrazin-2-yl)piperazine-1-carboxylate was as follows: tert-butyl 3'-chloro-2,3,5,6-tetrahydro-[1,2']bipyrazinyl-4-carboxylate (10 g, 33.4 mmol, 1 eq.) was dissolved in 1,4-dioxane (160 mL), and 4 M hydrochloric acid in 1,4- dioxane solution (80 mL, 0.3 mol, 10 eq.). The reaction mixture was stirred overnight at room temperature under nitrogen protection. Upon completion of the reaction, the reaction solution was diluted with dichloromethane (600 mL) and subsequently alkalized with 50% aqueous sodium hydroxide. The organic and aqueous layers were separated after addition of water (100 mL). The aqueous layer was extracted twice with dichloromethane (200 mL). All organic extracts were combined, washed with saturated aqueous sodium chloride, dried over anhydrous magnesium sulfate, filtered and concentrated to give 3'-chloro-3,4,5,6-tetrahydro-2H-[1,2']bis(pyrazinyl) product as a viscous oil, which solidified on standing (6.39 g, 96% yield). Mass spectrum (electrospray ionization): m/z = 199.1, 201.1 [M + H]+.

References

[1] Patent: WO2009/29439, 2009, A1. Location in patent: Page/Page column 14
[2] Patent: WO2008/141020, 2008, A1. Location in patent: Page/Page column 64
[3] Patent: WO2009/48765, 2009, A1. Location in patent: Page/Page column 10
[4] Journal of Medicinal Chemistry, 2012, vol. 55, # 11, p. 5467 - 5482
[5] Patent: WO2017/21879, 2017, A1. Location in patent: Page/Page column 114-115