Enantioselective Additions of Stabilized Carbanions to Imines Generated from α-Amido Sulfones By Using Lipophilic Salts of Chiral Tris(1,2-diphenylethylenediamine) Cobalt(III) Trications as Hydrogen Bond Donor Catalysts

The enantiopure salt Delta-[Co((S,S)-dpen)(3)](3+) 2Cl(-)BAr(f)(-)[BArf = B(3,5-C6H3(CF3)(2))(4)] is an effective hydrogen bond donor catalyst (10 mol%, r.t., CH2Cl2) for enantioselective additions of dialkyl malonates to Boc-derivatized aryl imines generated from sulfones [ArCH(SO2Ph)NHBoc] in the presence of K2CO3 (ten examples, 91-97% isolated yields, 87-99% ee). The diastereomeric salt Lambda-[Co((S,S)-dpen)(3)](3+) 2Cl(-)BAr(f20) [BArf20- = B(C6F5)(4)(-)] is similarly applied to additions of nitroalkanes (four examples, 89-93% isolated yields, 79-91% ee). Precautions to exclude air or moisture are unnecessary.