Asymmetric Reduction of Imines with Trichlorosilane, Catalyzed by Sigamide, an Amino Acid-Derived Formamide: Scope and Limitations<sup>†</sup>
作者:Andrei V. Malkov、Kvetoslava Vranková、Sigitas Stončius、Pavel Kočovský
DOI:10.1021/jo900561h
日期:2009.8.21
nonaromatic ketones 1−5, in which the steric difference between the alkyl groups R1 and R2 is sufficient. Simple nitrogen heteroaromatics (8a,b,d) exhibit low enantioselectivities due to the competing coordination of the reagent but increased steric hindrance in the vicinity of the nitrogen (8c,e) results in a considerable improvement. Cyclic imines 32d-d exhibited low to modest enantioselectivities.
酮亚胺的对映选择性还原6 - 10与三氯硅烷可通过催化Ñ甲基缬氨酸-衍生的路易斯碱性甲酰胺(小号- )23(Sigamide)高对映选择性(≤97%ee)和低催化剂载量(1-5摩尔%)在室温下在甲苯中。该反应是有效的与芳族胺(苯胺和茴香胺)和芳族,杂芳族,共轭的,并且甚至非芳族酮衍生的酮亚胺1 - 5,其中,所述烷基基团之间的位阻差R 1和R 2是足够的。简单氮杂芳族化合物(8a,b,d)由于试剂的竞争配位而显示出低对映选择性,但在氮(8c,e)附近的空间位阻增加,导致了相当大的改进。环状亚胺32d-d表现出低至中等的对映选择性。