Werner Complexes with ω-Dimethylaminoalkyl Substituted Ethylenediamine Ligands: Bifunctional Hydrogen-Bond-Donor Catalysts for Highly Enantioselective Michael Additions

The racemic carbonate complex [Co(en)2O2CO]+ Cl− (en=1,2‐ethylenediamine) and (S)‐[H3NCH((CH2)nNHMe2)CH2NH3]3+ 3 Cl− (n=1–4) react (water, charcoal, 100 °C) to give [Co(en)2((S)‐H2NCH((CH2)nNHMe2)CH2NH2)]4+ 4 Cl− (3 a–d H4+ 4 Cl−) as a mixture of Λ/Δ diastereomers that separate on chiral‐phase Sephadex columns. These are treated with NaOH/Na+ BArf− (BArf=B(3,5‐C6H3(CF3)2)4) to give lipophilic Λ‐ and Δ‐3 a–d3+ 3 BArf−, which are screened as catalysts (10 mol %) for additions of dialkyl malonates to nitroalkenes. Optimal results are obtained with Λ‐3 c3+ 3 BArf− (CH2Cl2, −35 °C; 98–82 % yields and 99–93 % ee for six β‐arylnitroethenes). The monofunctional catalysts Λ‐ and Δ‐[Co(en)3]3+ 3 BArf− give enantioselectivities of