Stereoselective Alkylations of Chiral Nitro Imine and Nitro Hydrazone Dianions. Synthesis of Enantiomerically Enriched 3-Substituted 1-Nitrocyclohexenes
作者:Scott E. Denmark*、Jeffrey J. Ares
DOI:10.1021/jo801790r
日期:2008.12.19
Dianions of chiral nitro imines (generated by a combination of LDA and s-BuLi) underwent diastereoselective alkylation with methyl, butyl, isopropyl, allyl, and methallyl iodides. In contrast to the behavior of simple metalloenamines, the most selective auxiliary contained no coordinating groups but did possess a large steric difference between the two substituents. The yield and selectivity of the
手性硝基亚胺的二价阴离子(由 LDA 和 s-BuLi 组合生成)与甲基、丁基、异丙基、烯丙基和甲代烯丙基碘进行非对映选择性烷基化。与简单金属烯胺的行为相反,最具选择性的助剂不含配位基团,但两个取代基之间确实具有较大的空间差异。通过添加 HMPA 或 DMPU 提高了烷基化反应的产率和选择性。使用(S)-1-萘基乙胺作为助剂提供了烷基化产物的R绝对构型。这种立体化学结果可以通过简单的空间方法控制构象固定、内部配位的双阴离子中的烷基化来合理化。 SAMP 硝基腙的收率和选择性较差。