title: Enantioselective 1,3-dipolar cycloaddition of C,N-cyclic azomethine imines to unsaturated nitriles catalyzed by NiII-Pigiphos.
abstract: The asymmetric 1,3-dipolar cycloaddition reaction of C,N-cyclic azomethine imines with small unsaturated nitriles using a dicationic Ni(II) complex containing the chiral triphosphine ligand bis{(R)-1-[(Sp)-2-(diphenylphosphino)ferrocenyl]ethyl}cyclohexylphosphine [(R,Sp)-Pigiphos] as a catalyst has been developed. A variety of new chiral cyanopyrazolidines were obtained regio- and diastereoselectively in good to excellent yields with moderate to excellent enantioselectivities. Thus, N-benzoylimino-3,4-dihydro-6-methylisoquinolinium betaine (1a) reacts at RT with acrylonitrile in the presence of 1-5 mol % catalyst to afford 3,4-trans-1-benzoyl-4-cyano-2,3-(tetrahydroisoquinoline)tetrahydropyrazole (2a) in up to 84% yield and 98% ee. The regio- and stereoselectivity were confirmed in the case of compound 2a and 3,4-trans-1-benzoyl-4-cyano-2,3-(6-bromotetrahydroisoquinoline)tetrahydropyrazole (2e) by X-ray crystallography.
authors.affiliation: Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, ETH Zürich , CH-8093 Zürich, Switzerland.
authors.forename: Sandra
authors.initials: S
authors.lastname: Milosevic
authors.forename: Antonio
authors.initials: A
authors.lastname: Togni
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D061565:Cycloaddition Reaction; D007097:Imines / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D009570:Nitriles / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D013882:Thiosemicarbazones / Q000737:chemistry*
chemical_list: D001391:Azo Compounds; D007097:Imines; D008024:Ligands; D009570:Nitriles; D009942:Organometallic Compounds; D013882:Thiosemicarbazones; C512188:azomethine; D009532:Nickel