Enantioselective homoallyl-cyclopropanation of dibenzylideneacetone by modified allylindium halide reagents—rapid access to enantioenriched 1-styryl-norcarene
作者:Guy C. Lloyd-Jones、Philip D. Wall、Jennifer L. Slaughter、Alexandra J. Parker、David P. Laffan
DOI:10.1016/j.tet.2006.05.003
日期:2006.12
ligands have been tested as stoichiometric asymmetric modifiers for this process. Enantiopure compounds such as cinchona alkaloids, ephedra, aminoalcohols and tartaric acid derivatives, which have proven of utility as asymmetric modifiers for the indium-mediated allylation of aldehydes and ketones, were very inefficient in the process 8→9. However, mandelic acid derivatives, in particular mandelates, were
二亚苄基丙酮(8)与原位生成的烯丙基卤化试剂反应生成均烯丙基环丙烷化反应的产物:2-(3''-丁烯基)-1,1-双[(E)-2'-苯基乙烯基]环丙烷(9),其通过逐步分离CO键和从试剂中递送两个烯丙基片段来进行。已经测试了一系列对映体富集的配体作为该过程的化学计量不对称改性剂。对映纯化合物,例如金鸡纳生物碱,麻黄,氨基醇和酒石酸衍生物,已被证明可用作铟介导的醛和酮的烯丙基化的不对称改性剂,但在此过程中效率很低8 → 9。然而,发现扁桃酸衍生物,特别是扁桃酸酯具有很大的潜力。环丙烷9的绝对立体化学已通过降解为1,1-二羧甲基-2-丁基环丙烷,并从己烯开始进行独立的对映选择性合成来确定。在优化的条件下,即。使用烯丙基碘化试剂并与Na 2 SO 3水溶液进行后处理以避免碘介导的聚合,可以以86%的收率生成(S)-9,并使用(S)扁桃酸甲酯作为改性剂有用的对映体纯度(94/6 er ) 被观测到。