Campbell Nathaniel R, Sun Bingfeng, Singh Ravi P, Deng Li
Department of Chemistry, Brandeis University, 415 South St., Waltham, MA 02454-9110, USA.
Adv Synth Catal. 2011 Nov 1;353(17):3123-3128. doi: 10.1002/adsc.201100447.
Δ-Pyrazolines are of significant medicinal and synthetic interest due to their therapeutic properties and utility in the synthesis of 1,3-diamines, yet few asymmetric methods exist to prepare them. An unprecedented highly enantioselective organocatalytic synthesis of 2-pyrazolines was achieved through an asymmetric conjugate addition catalyzed by 9--amino cinchona alkaloids followed by deprotection-cyclization, which furnished chiral 2-pyrazolines in 46-78% yield and 59-91% ee. This bifunctional catalytic methodology thus provides easy access to considerable range of optically active 3,5-dialkyl 2-pyrazolines.
由于其治疗特性以及在1,3 - 二胺合成中的用途，δ - 吡唑啉具有重要的药用和合成价值，但制备它们的不对称方法却很少。通过9 - 氨基金鸡纳生物碱催化的不对称共轭加成，随后进行脱保护 - 环化反应，实现了前所未有的2 - 吡唑啉的高度对映选择性有机催化合成，得到了产率为46 - 78%、对映体过量值为59 - 91%的手性2 - 吡唑啉。因此，这种双功能催化方法为大量光学活性的3,5 - 二烷基2 - 吡唑啉提供了简便的合成途径。
