Enantioselective borane reduction of ketones catalyzed by tricyclic 1,3,2-oxazaborolidines
作者:Johannes Kaldun、Alexander Krimalowski、Matthias Breuning
DOI:10.1016/j.tetlet.2016.04.091
日期:2016.6
5/5/6-ring system with the B–N bond forming one ring junction. In the asymmetric borane reduction of ketones, the B-alkoxy bridged derivative permits excellent enantioselectivities of up to 98% ee and its activity is comparable to that of the standard CBS catalyst. The closely related, B-alkyl bridged derivative is less enantioselective and less active, as determined by competition experiments.
从Boc- 1-焦谷氨酸甲酯分七个步骤合成了两个新颖的三环1,3,2-恶唑硼烷。它们的特征在于由邻和围稠合的5/5/6环系统与B-N键形成一个环结。在酮的不对称硼烷还原中,B-烷氧基桥接的衍生物可实现高达98%ee的出色对映选择性,其活性可与标准CBS催化剂媲美。如竞争实验所确定的,密切相关的B-烷基桥接的衍生物对映选择性较低且活性较低。