Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA.
Angew Chem Int Ed Engl. 2012 Sep 24;51(39):9886-90. doi: 10.1002/anie.201205233. Epub 2012 Aug 31.
Positive water effect: A catalyst composed of [Pd(2)(dba)(3)] (dba=dibenzylideneacetone) and (S)-Siphos-PE is effective for the enantioselective coupling of N-allyl ureas with aryl bromides to afford 4-substituted imidazolidin-2-ones. Added water leads to significantly improved enantioselectivities with electron-poor aryl halide substrates. It is suggested that the C-C bond-forming reductive elimination is the enantiodetermining step in these reactions.
由[Pd(2)(dba)(3)](dba=dibenzylideneacetone)和(S)-Siphos-PE 组成的催化剂可有效用于 N-烯丙基脲与芳基溴化物的对映选择性偶联,得到 4-取代的咪唑烷-2-酮。加入水后,对缺电子芳基卤化物底物的对映选择性有显著提高。反应中 C-C 键形成的还原消除步骤被认为是决定对映体选择性的步骤。