Asymmetric Samarium-Reformatsky Reaction of Chiral α-Bromoacetyl-2-oxazolidinones with Aldehydes
作者:Shin-ichi Fukuzawa、Hiroshi Matsuzawa、Shin-ichi Yoshimitsu
DOI:10.1021/jo9914317
日期:2000.3.1
samarium(II) iodide mediated asymmetric Reformatsky-type reaction of chiral 3-bromoacetyl-2-oxazolidinones with various aldehydes was studied. A series of chiral 4-substituted 2-oxazolidinones 1-3 and 5,5-disubstituted "SuperQuat" oxazolidinones 4-5 were employed as chiral auxiliaries of the alpha-bromoacetic acid. The reaction of 1 with various aldehydes gave the alpha-unbranched beta-hydroxy carboximides
研究了碘化sa(II)介导的手性3-溴乙酰基-2-恶唑烷酮与各种醛类的不对称Reformatsky型反应。一系列手性的4-取代的2-恶唑烷酮1-3和5,5-二取代的“ SuperQuat”恶唑烷酮4-5用作α-溴乙酸的手性助剂。1与各种醛的反应以高收率和高非对映异构体过量值(高达> 99%de)得到了α-支链的β-羟基羧酰亚胺。源自5,5-二苯基SuperQuat 5的大多数反应产物具有高度结晶性。一次重结晶可得到非对映体纯产物,而其他非对映体则无法通过光谱法检测到。β-羟基羧酰亚胺的绝对构型通过参考文献值通过相应的已知乙酯的旋光度来确定。在温和条件下,使用氢氧化锂很容易实现从辅助SuperQuats水解掉附加的β-羟基部分。得到的相应羧酸和返回的SuperQuats收率很高,没有任何消旋作用的迹象。反应的第一步是还原α-溴基团以生成烯醇,后者会增加醛的含量。发现来自苯甲醛的加合物(7i)