Department of Chemistry, Texas A&M University, PO Box 30012, College Station, TX, 77842-3012, USA.
Institut für Organische Chemie and Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Henkestrasse 42, 91054, Erlangen, Germany.
Angew Chem Int Ed Engl. 2016 Mar 18;55(13):4356-60. doi: 10.1002/anie.201511314. Epub 2016 Feb 25.
The racemic carbonate complex Co(en)2 O2 CO Cl(-) (en=1,2-ethylenediamine) and (S)-H3 NCH((CH2 )n NHMe2 )CH2 NH3 3 Cl(-) (n=1-4) react (water, charcoal, 100 °C) to give Co(en)2 ((S)-H2 NCH((CH2 )n NHMe2 )CH2 NH2 ) 4 Cl(-) (3 a-d H(4+) 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-C6 H3 (CF3 )2 )4 ) to give lipophilic Λ- and Δ-3 a-d(3+) 3 BArf (-) , which are screened as catalysts (10 mol %) for additions of dialkyl malonates to nitroalkenes. Optimal results are obtained with Λ-3 c(3+) 3 BArf (-) (CH2 Cl2 , -35 °C; 98-82 % yields and 99-93 % ee for six β-arylnitroethenes). The monofunctional catalysts Λ- and Δ-Co(en)3 3 BArf (-) give enantioselectivities of <10 % ee with equal loadings of Et3 N. The crystal structure of Δ-3 a H(4+) 4 Cl(-) provides a starting point for speculation regarding transition-state assemblies.
外消旋碳酸盐配合物 Co(en)2 O2 CO Cl(-)（en=1,2-乙二胺）和 (S)-H3 NCH((CH2 )n NHMe2 )CH2 NH3 3 Cl(-)（n=1-4）在水、木炭存在下于 100℃反应，得到Co(en)2 ((S)-H2 NCH((CH2 )n NHMe2 )CH2 NH2 ) 4 Cl(-)（3a-dH(4+) 4 Cl(-)），其为 Λ/Δ 非对映异构体混合物，在手性 Sephadex 柱上分离。这些混合物用 NaOH/Na(+) BArf (-)（BArf =B(3,5-C6 H3 (CF3 )2 )4 ）处理，得到亲脂性 Λ-和 Δ-3a-d(3+) 3 BArf (-)，其被筛选为二烷基丙二酸酯与硝基烯烃加成反应的催化剂（10mol%）。使用 Λ-3c(3+) 3 BArf (-)（CH2 Cl2 ，-35℃；六个 β-芳基硝基乙烯的收率为 98-82%，对映选择性为 99-93%ee）得到最佳结果。单功能催化剂 Λ-和 Δ-Co(en)3 3 BArf (-) 具有相等负载量的 Et3 N 时对映选择性小于 10%ee。Δ-3a H(4+) 4 Cl(-)的晶体结构为推测过渡态组装提供了起点。
