Alkylations of Chiral Nickel(II) Complexes of Glycine under Phase‐Transfer Conditions

Alkylation reactions of nickel(II) complex 6 derived from glycine and 2‐[(1‐benzyl‐ L ‐prolyl)amino]benzophenone (BPBP) were studied under phase‐transfer‐catalysis (PTC) conditions. The goal of this work was to find an alternative suitable solvent for these reactions to replace the commonly used CH 2 Cl 2 which leads to the formation of several by‐products, thus lowering the yield of target compounds. We demonstrate that 1,2‐dichloroethane is a markedly better solvent providing higher yields (75–99%) of the desired products 10 with 36–88% diastereoisomer purity ( Scheme 3 and Table ). Furthermore, we show that the stereochemical outcome of these PTC reactions (kinetic control) can be easily improved to >95% de by treatment of the PTC products with MeONa/MeOH. The scope of these reactions includes alkylations with methyl iodide as well as activated halides such as benzyl, allyl or propargyl, bromides and most notably ethyl 2‐bromoacetate ( Table ).