Stereoselective Alkylidenation of Ketones with 2-(<i>p</i>-Toluenesulfinyl)benzyl Iodide: Synthesis of Enantiomerically Pure Trisubstituted Epoxides

Alkylidenation of arylmethyl, dialkyl, and cyclic ketones with 2-(p-toluenesulfinyl)benzyl iodide in the presence of NaN(SiMe3)2 takes place with a high or complete control of the facial selectivity at the carbonyl group (up to 98% de) and the carbanion (>98% de), respectively, yielding mixtures of only two optically pure trisubstituted epoxides (E/Z ratio ranges between 2:1 and >50:1). Removal of the p-tolylsulfinyl group with t-BuLi provides the corresponding (E)-3-phenyl-2,2-disubstituted epoxides without affecting their optical purity.在六甲基二硅基胺基钠（NaN(SiMe3)2）存在下，2-(对甲苯亚磺酰基)苄基碘与芳基甲基酮、二烷基酮及环酮发生亚烷基化反应。该反应对羰基位点与碳负离子位点的面选择性分别实现了优异乃至完全的控制，二者的非对映体过量率（de）最高可达98%与>98%，仅生成两种光学纯的三取代环氧化物的混合物，其E/Z构型比介于2:1至>50:1之间。采用叔丁基锂（t-BuLi）脱去产物中的对甲苯亚磺酰基后，可得到对应的(E)-3-苯基-2,2-二取代环氧化物，且不会影响其光学纯度。