Asymmetric electrophilic α-amidoalkylation - 10: a new camphorimide derived chiral auxiliary for the Asymmetric Synthesis with N-acyliminium ions - preparation of aracemic 2-Substituted Piperidines.
作者:Klaus Th. Wanner、Franz F. Paintner
DOI:10.1016/s0040-4020(01)81110-8
日期:1994.3
Compound 5 is a new α-amidoalkylation reagent for the asymmetric synthesis of 2-substituted piperidines. Its chiral auxiliary 3 is derived from camphoric acid and designed for an asymmetric induction mechanism featuring precomplexation as the decisive step for stereodifferentiation. Reagent 5 can smoothly be alkylated with various organometallic reagents after its activation by HCl-addition which presumably
化合物5是用于2-取代的哌啶的不对称合成的新的α-酰胺基烷基化试剂。它的手性助剂3衍生自樟脑酸,设计用于不对称诱导机理,其特征在于预复合是立体分化的决定性步骤。试剂5在通过HCl加成活化后,可以用各种有机金属试剂平稳地烷基化,这大概会产生α-氯酰胺6。有机锌和有机铝化合物似乎能提供最佳结果,其非对映选择性最高,乙基化为77.8 / 2.2(7a / 8a),甲基化为87.7 / 12.3(7b / 8b)),96.5 / 3.5的丁基化(7C / 8C)和90.4 / 9.6为苯基化(7D / 8D的)5。可以通过除去手性助剂从α-酰胺基烷基化产物7a-d获得相应的旋光的2-取代的氯化氯化吡啶鎓9d-d,该除去可以通过用LiAlH 4还原或通过用KOH水解来完成。