Recyclable Copper Catalysts Based on Imidazolium-Tagged Bis(oxazolines): A Marked Enhancement in Rate and Enantioselectivity for Diels–Alder Reactions in Ionic Liquid
作者:Simon Doherty、Peter Goodrich、Christopher Hardacre、Julian G. Knight、Mimi T. Nguyen、Vasile I. Pârvulescu、Cristina Paun
DOI:10.1002/adsc.200600531
日期:2007.4.2
Imidazolium-tagged bis(oxazolines) have been prepared and used as chiral ligands in the copper(II)-catalysed Diels–Alder reaction of N-acryloyl- and N-crotonoyloxazolidinones with cyclopentadiene and 1,3-cyclohexadiene in the ionic liquid 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, [emim][NTf2]. A significant and substantial enhancement in the rate and enantioselectivity was achieved
制备了咪唑鎓标记的双(恶唑啉),并用作离子液体中铜(II)催化的N-丙烯酰基-和N-巴豆酰基恶唑烷二酮与环戊二烯和1,3-环己二烯的铜(II)催化Diels-Alder反应中的手性配体。乙基-3-甲基咪唑鎓双[(三氟甲基)磺酰基]酰亚胺,[emim] [NTf 2 ]。与二氯甲烷相比,[emim] [NTf 2 ]的反应速率和对映选择性显着提高。例如,在[emim] [NTf 2 ]中2分钟内,N-丙烯酰基恶唑烷酮与环戊二烯之间的反应获得了高达95%的完全转化率和对映选择性。],而在二氯甲烷中的相应反应则需要60分钟才能完全完成,ee仅为16%。在离子液体中获得的提高的速率使得催化剂负载量低至0.5 mol%,可以在2分钟内完全转化,同时保持相同水平的对映选择性。咪唑鎓标记的催化剂可以循环使用十次而没有任何活性或对映选择性的损失,并且在循环过程中对离子液相的亲和性比类似的不带电荷的配体高得多。