New Mono-Quarternized Bis-Cinchona Alkaloid Ligands for Asymmetric Dihydroxylation of Olefins in Aqueous Medium: Unprecedented High Enantioselectivity and Recyclability
作者:Doo Seung Choi、Sang Seop Han、Eun Kyung Kwueon、Han Young Choi、Soon Ho Hwang、Yil Sung Park、Choong Eui Song
DOI:10.1002/adsc.200600253
日期:2006.12
bis-Cinchona alkaloid ligands, [(QD)2PHAL-Allyl]Br and [(QN)2PHAL-Allyl]Br, have been synthesized which can be converted into their highly water-soluble multihydroxylated derivatives under asymmetric dihydroxylation (AD) conditions and, thus, easily recovered by a simple extraction method after reaction and reused. These mono-quaternized ligands exhibited superior catalytic efficiency to their neutral counterparts
合成了双金鸡纳生物碱配体的新的单季铵化的烯丙基溴盐,[(QD)2 PHAL-烯丙基] Br和[(QN)2 PHAL-烯丙基] Br,它们可以转化为高度水溶性的多羟基化盐衍生物在不对称二羟基化(AD)条件下,因此在反应后可通过简单的提取方法轻松回收并重复使用。这些单季铵化的配体表现出比其中性对应物(DHQD)2 PHAL和(DHQ)2更高的催化效率PHAL用于在Upjohn条件下单和二取代苯乙烯的AD反应。仅0.1 mol%的was就足以完成单取代和二取代的苯乙烯的反应,此外,这些配体显示出最高的对映选择性(例如,对于苯乙烯,具有[(QD)2 PHAL-烯丙基] Br的ee为97%ee)在Upjohn条件下取得的成就。