HYDROBORATION .83. SYNTHESIS AND HYDROBORATION OF 2-ETHYLAPOPINENE - COMPARISON OF MONOISOPINOCAMPHEYLBORANE AND ITS 2-ETHYL ANALOG FOR THE CHIRAL HYDROBORATION OF REPRESENTATIVE ALKENES
HYDROBORATION .83. SYNTHESIS AND HYDROBORATION OF 2-ETHYLAPOPINENE - COMPARISON OF MONOISOPINOCAMPHEYLBORANE AND ITS 2-ETHYL ANALOG FOR THE CHIRAL HYDROBORATION OF REPRESENTATIVE ALKENES
复制标题
DOI：
10.1021/jo00258a021
复制
发表时间：
1988-11-11
影响因子：
3.6
通讯作者：
PERUMAL, PT
中科院分区：
文献类型：
--
作者：
BROWN, HC;RANDAD, RS;PERUMAL, PT
诺卜醇甲苯磺酸酯的还原得到新的手性配体（-）-2-乙基lapopinene（90.2%ee），具有更高的空间要求比-pinene。硼烷与（-）-2-乙基Lapopinene在THF中于0 ℃下以1：2的摩尔比反应，得到单-和二烷基硼烷EapBH 2和Eap 2BH的平衡混合物.使用过量的（-）-2-乙基Lapopinene（1：10; BMS/2-乙基Lapopinene），双（2-乙基Lapoisopinocamphyl）硼烷Eap 2BH的形成基本上是定量的（~ 98%）。在34 ℃下用TMED处理硼烷（Eap 2BH，EapBH 2）的平衡混合物，析出结晶（EapBH 2）2-TMED。用BF 3-OEt 2处理结晶产物得到基本上100%ee的EapBH 2（单（2-乙基Lapoisopinocamphyl）硼烷），其对映体纯度高于用于制备的（-）-2-乙基Lapopinene（~ 90%ee）。用EapBH 2对一系列烯烃进行硼氢化，然后氧化中间体有机硼烷，产生相应的醇，其对映体纯度比在相同条件下用IpcBH 2实现的那些醇显著提高。从纯化的EapBH 2释放烯烃提供高光学纯度（> 99%ee）的㈠-2-乙基Lapopinene（[n] 23 D-46.2（纯的））。（+）-α-蒎烯（[α] 23 D + 51.4（净））与Lochmann试剂的金属化，随后与碘甲烷的烷基化，提供了高光学纯度（> 99%ee）的（+）-2-乙基Lapopinene（[α] 23 D + 46.4（净）），其可从商业（-）-nopol获得。
Reduction of nopol tosylate gives the new chiral ligand (-)-2-ethylapopinene (90.2% ee) with higher steric requirements than those of-pinene. Reaction of borane with (-)-2-ethylapopinene in THF at 0 C, in a molar ratio of 1: 2, provides an equilibrium mixture of mono- and dialkylboranes EapBH2 and Eap2BH. With an excess of (-)-2-ethylapopinene (1: 10; BMS/2-ethylapopinene), the formation of bis (2-ethylapoisopinocampheyl) borane, Eap2BH, is essentially quantitative (~ 98%). Treatmentof the equilibrium mixture of boranes (Eap2BH, EapBH2) with TMED at 34 C precipitates crystalline (EapBH2) 2-TMED. Treatment of the crystalline product with BF3-OEt2 gives EapBH2 (mono (2-ethylapoisopinocampheyl) borane) of essentially 100% ee, enantiomerically purer than the (-)-2-ethylapopinene (~ 90% ee) utilized for the preparation. Hydroboration of a series of olefins with EapBH2, followed by oxidation of the intermediate organoborane, produces the corresponding alcohols with significantly improved enantiomeric purities over those realized with IpcBH2 under the same conditions. Liberation of the olefin from purified EapBH2 provides (-)-2-ethylapopinene ([«] 23D-46.2 (neat)) in high optical purity (> 99% ee). Metalation of (+)-a-pinene ([a] 23D+ 51.4 (neat)) with the Lochmannreagent, followed by alkylation with methyl iodide, provides in high optical purity (> 99% ee)(+)-2-ethylapopinene ([a] 23D+ 46.4 (neat)), unavailable from commercial (-)-nopol.