作者:Akira Yanagisawa、Tetsuo Kikuchi、Takeshi Kuribayashi、Hisashi Yamamoto
DOI:10.1016/s0040-4020(98)00482-7
日期:1998.8
New chiral proton sources possessing an asymmetric 2-oxazoline ring, (S,S)-imide 1 and related imides, were synthesized from Kemp's triacid and optically active 2-amino alcohols. With these chiral imides, various lithium enolates of α-monoalkylated cycloalkanones were effectively protonated with excellent to moderate enantioselectivity. An increase in enantioselectivity was observed in the asymmetric
由肯普氏三酸和旋光性2-氨基醇合成了具有不对称2-恶唑啉环,(S,S)-酰亚胺1和相关酰亚胺的新手性质子源。使用这些手性酰亚胺,可以以优异的中度对映选择性有效地质子化α-单烷基化环烷酮的各种烯醇锂。使用锂盐作为添加剂,在用(S,S)-酰亚胺1制备的手性烯醇盐的不对称质子化中,观察到对映选择性的增加。例如,当甲硅烷基烯醇醚时,以90%ee以高收率获得了富含(R)的2-正戊基环戊酮35在5当量的LiBr在Et 2 O中存在下,用n- BuLi处理33,然后通过(S,S)-酰亚胺1在THF中的溶液使所得的烯醇锂34质子化。相反,在没有LiBr的情况下获得的产物35表现出较低的对映体过量(74%ee)。