Efficient construction of biaryls and macrocyclic cyclophanes via electron-transfer oxidation of Lipshutz cuprates
Efficient construction of biaryls and macrocyclic cyclophanes via electron-transfer oxidation of Lipshutz cuprates
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DOI：
10.1021/jo0608063
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发表时间：
2006-08-04
影响因子：
3.6
通讯作者：
Iyoda, Masahiko
中科院分区：
文献类型：
--
作者：
Miyake, Yoshihiro;Wu, Mo;Iyoda, Masahiko
公开了一种通过电子转移氧化Lipshutz铜酸盐（Ar2Cu(CN)Li-2）与有机电子受体进行芳基卤化物均偶联的有效方法。因此，用叔丁基锂和CuCN连续处理芳基或杂芳基溴制得各种类型的Lipshutz铜酸盐。Lipshutz铜酸盐与对苯醌的电子转移氧化反应顺利进行，得到相应的均偶联产物，产率中等至较高。此外，它可以应用于构建噻吩或苯融合的10元环。为了合成10元环烷，应在双金属环中间体中保持Lipshutz铜酸盐的线性C-Cu-C结构，有效地生成大环烷。环烷的x射线分析表明，桥接原子的不同导致了大环的不同构象。因此，硅桥环烷5a具有d -2对称结构，具有四个噻吩环的扭曲斜方阵排列，而亚甲基和氧桥环烷5b和5c具有C2h和c -2对称结构，分别具有椅子状和船状构象。c -2对称5c的H-1核磁共振谱与温度有关，构象变化的活化能（δ G双dagger）为10.1 kcal/mol。
An efficient method for the homocoupling of aryl halides by electron-transfer oxidation of Lipshutz cuprates (Ar2Cu(CN)Li-2) with organic electron acceptors is disclosed. Thus, various types of Lipshutz cuprates are prepared by successive treatment of aryl or heteroaryl bromides with tert-butyllithium and CuCN. The electron-transfer oxidation of Lipshutz cuprates with p-benzoquinones proceeds smoothly to afford the corresponding homocoupling products in moderate to good yields. Furthermore, it can be applied to the construction of either thiophene- or benzene-fused 10-membered ring cyclophanes. For the synthesis of 10-membered cyclophanes, the linear C-Cu-C structure of Lipshutz cuprates should be maintained in the dimetallacyclic intermediates, producing the large ring cyclophanes efficiently. The X-ray analysis of the cyclophanes reveals that the difference in the bridging atoms results in the different conformations of the macrocyclic rings. Thus, the silicon-bridged cyclophane 5a adopts a D-2-symmetric structure with a twisted rhombic arrangement of four thiophene rings, whereas the methylene- and oxygen-bridged cyclophanes 5b and 5c possess C2h- and C-2-symmetric structures with chair- and boatlike conformations, respectively. The H-1 NMR spectrum of C-2-symmetric 5c is temperature- dependent, and the activation energy (Delta G double dagger) for the conformational change is 10.1 kcal/mol.