Stereoselective alkylations of chiral nitro imine and nitro hydrazone dianions. Synthesis of enantiomerically enriched 3-substituted 1-nitrocyclohexenes.
Stereoselective alkylations of chiral nitro imine and nitro hydrazone dianions. Synthesis of enantiomerically enriched 3-substituted 1-nitrocyclohexenes.
复制标题
手性硝基亚胺和硝基腙二价阴离子的立体选择性烷基化。
DOI：
10.1021/jo801790r
复制
发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Ares,JeffreyJ
中科院分区：
文献类型：
--
作者：
Denmark,ScottE;Ares,JeffreyJ
手性硝基亚胺的diions（由LDA和- buli组合生成）与甲基、丁基、异丙基、烯丙基和甲基碘化物进行非对映选择性烷基化。与简单金属胺的行为相反，最具选择性的助剂不含配位基，但在两个取代基之间具有较大的空间差异。HMPA和DMPU的加入提高了烷基化反应的收率和选择性。采用(S)-1-萘乙胺作为助剂，得到了烷基化产物的绝对构型。这种立体化学结果可以通过在构象固定的、内部配位的离子中进行简单的立体方法控制的烷基化来合理化。SAMP硝基腙的产率和选择性较差。
Dianions of chiral nitro imines (generated by a combination of LDA ands-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 alkylations were improved by the addition of HMPA or DMPU. The use of (S)-1-naphthylethylamine as the auxiliary afforded theRabsolute configuration of the alkylation products. This stereochemical outcome could be rationalized by simple steric approach controlled alkylation in a conformationally fixed, internally coordinated dianion. A SAMP nitro hydrazone gave poorer yields and selectivities.