Bifunctional Amine-Squaramides as Organocatalysts in Michael/Hemiketalization Reactions of β,γ-Unsaturated α-Ketoesters and α,β-Unsaturated Ketones with 4-Hydroxycoumarins
作者:Viktória Modrocká、Eva Veverková、Mária Mečiarová、Radovan Šebesta
DOI:10.1021/acs.joc.8b01847
日期:2018.11.2
Michael/hemiketalization reactions of 4-hydroxycoumarines with two types of enones. Tertiary amine-squaramide organocatalysts afforded the best results regarding both activity and enantioselectivity when β,γ-unsaturated α-ketoesters were used as the Michael acceptors (yields up to 98%, enantioselectivities up to 90% ee). On the other hand, the primary amine-squaramides are the best choice for related reactions of 4-hydroxycoumarins
在4-羟基香豆素与两种类型的烯酮的迈克尔/半缩合反应中测试了各种胺-方酸酰胺的催化效率。当使用β,γ-不饱和α-酮酸酯作为Michael受体时,叔胺-方酰胺有机催化剂在活性和对映选择性方面均提供了最佳结果(产率高达98%,对映选择性高达90%ee)。另一方面,伯胺-方胺是4-羟基香豆素与烯酮相关反应的最佳选择。以高对映体纯度(最高96%)获得了相应的吡喃并[3,2 - c ] chromen-5-on产物。将4-羟基香豆素迈克尔加成到4-苯基丁-3-烯-2-上直接生产的手性抗凝药物(S当使用绿色溶剂2-MeTHF和催化剂(S,S)-C8时,在92%ee中的)-华法林。此外,对映体催化剂(R,R)-C 8得到的(R)-华法林的ee> 99%。