title: Complete regioselective addition of grignard reagents to pyrazine N-oxides, toward an efficient enantioselective synthesis of substituted piperazines.
abstract: A conceptually new one-pot strategy for the synthesis of protected substituted piperazines via the addition of Grignard reagents to pyrazine N-oxides is presented. This strategy is high yielding (33-91% over three steps), step-efficient, and fast. The synthesized N,N-diprotected piperazines are convenient to handle and allow for orthogonal deprotection at either nitrogen for selective transformations. In addition, this is a synthetic route to enantiomerically enriched piperazines by using a combination of phenyl magnesium chloride and (-)-sparteine, which resulted in enantiomeric excesses up to 83%.
authors.affiliation: Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden.
authors.forename: Hans
authors.initials: H
authors.lastname: Andersson
authors.forename: Thomas Sainte-Luce
authors.initials: TS
authors.lastname: Banchelin
authors.forename: Sajal
authors.initials: S
authors.lastname: Das
authors.forename: Magnus
authors.initials: M
authors.lastname: Gustafsson
authors.forename: Roger
authors.initials: R
authors.lastname: Olsson
authors.forename: Fredrik
authors.initials: F
authors.lastname: Almqvist
mesh_terms: D007202:Indicators and Reagents / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010879:Piperazines / Q000138:chemical synthesis* / Q000737:chemistry; D011719:Pyrazines / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D007202:Indicators and Reagents; D009942:Organometallic Compounds; D010087:Oxides; D010879:Piperazines; D011719:Pyrazines