Triethylborane-mediated reactions of lithium enolates derived from chiral N-acyloxazolidinones with ethyl difluoroiodoacetate allows easy access to α-(ethoxycarbonyl)difluoromethylated carboximides with good diastereomeric excess (86->98%de). The stereochemistry of the (ethyoxycarbonyl)difluoromethylated carboximides indicates that the (ethoxycarbonyl)difluoromethyl radical generated from ethyl difluoroiodoacetate and triethylborane reacts preferentially on the si face of the lithium enolates.
三乙基
硼烷介导的反应将来自手性N-酰氧
喹啉的
锂烯醇盐与
二氟碘乙酸乙酯结合,可以轻松获得α-(乙氧基羧基)二
氟甲基化的羧
亚胺,且具有良好的愈合对映体过量(86->98% de)。(乙氧基羧基)二
氟甲基化的羧
亚胺的立体
化学表明,来自
二氟碘乙酸乙酯和三乙基
硼烷生成的(乙氧基羧基)
二氟甲基自由基优先在
锂烯醇盐的si面上反应。