North Michael, Watson James M
School of Chemistry, Newcastle University Bedson Building, Newcastle upon Tyne, NE1 7RU (UK).
ChemCatChem. 2013 Aug;5(8):2405-2409. doi: 10.1002/cctc.201300215. Epub 2013 May 28.
Structurally well-defined bimetallic titanium(IV) (salen) and monometallic vanadium(V) (salen) complexes have been used as catalysts for the asymmetric addition of trimethylsilyl cyanide to β-nitroalkenes to produce chiral nitronitriles with values in the range of 79-89 % and conversions up to 100 % at 0 °C. The reaction conditions (solvent, temperature, time and vanadium complex counter-ion) were optimised, and it was shown that the catalyst loading could be significantly reduced (20 to 2 mol %) and the reaction temperature increased (-40 to 0 °C) compared to previous studies that used an in situ prepared catalyst. The results are compared and contrasted with previous results obtained by using the same catalysts for the asymmetric addition of trimethylsilyl cyanide to aldehydes, and a transition-state structure for the asymmetric addition of trimethylsilyl cyanide to nitroalkenes is proposed to account for the observed stereochemistry.
结构明确的双金属钛（IV）（水杨醛缩邻氨基酚）和单金属钒（V）（水杨醛缩邻氨基酚）配合物已被用作催化剂，用于将三甲基硅基氰不对称加成到β-硝基烯烃上，以制备手性硝腈，其对映体过量值在79 - 89%范围内，在0°C时转化率高达100%。优化了反应条件（溶剂、温度、时间和钒配合物抗衡离子），结果表明，与使用原位制备催化剂的先前研究相比，催化剂负载量可显著降低（从20%降至2%），反应温度可提高（从 - 40°C升至0°C）。将这些结果与先前使用相同催化剂将三甲基硅基氰不对称加成到醛上所获得的结果进行了比较和对比，并提出了三甲基硅基氰不对称加成到硝基烯烃的过渡态结构，以解释所观察到的立体化学现象。
