Lewis acid-mediated SN2 type displacement by grignard reagents on chiral perhydropyrido[2,1-b]pyrrolo[1,2-d][1,3,4]oxadiazine. Chirality induction in asymmetric synthesis of 2-substituted piperidines
作者:Naoki Yamazaki、Chihiro Kibayashi
DOI:10.1016/s0040-4039(97)00991-x
日期:1997.6
Et2AlCl-mediated nucleophilic alkylation with Grignard reagents on chiral perhydropyrido[2,1-b]pyrrolo[1,2-d][1,3,4]oxadiazine has proved to proceed via an SN2 mechanism at low temperatures (below −80 °C) with high to excellent inversive stereoselection, while, at an elevated temperature, hydrazonium ions are formed preferentially leading to retentive stereoselection. This methodology provides useful
用格氏试剂在手性过氢吡啶并[ 2,1 - b ]吡咯并[1,2- d ] [1,3,4]恶二嗪上进行Et 2 AlCl介导的亲核烷基化反应是在低温下通过S N 2机理进行的(低于-80°C)时具有很高的反演立体选择效果,而在升高的温度下会优先生成离子,从而导致保持性立体选择。该方法学为2-取代的哌啶的对映选择性的制备提供了有用的途径,并且用于(+)-亚氨酸的不对称合成。