Enantioselective radical cyclisation reactions of 4-substituted quinolones mediated by a chiral template
作者:Aline Bakowski、Martina Dressel、Andreas Bauer、Thorsten Bach
DOI:10.1039/c0ob01272f
日期:——
Six 4-substituted quinolones 6–8, which bear an ω-iodoalkyl chain, were prepared and subjected to reductive radical cyclisation conditions employing BEt3/O2 as the initiator and either Bu3SnH or TMS3SiH as hydride source. 4-(4-Iodobutyl)-quinolone (6a) and 4-(3-iodopropylthio)-quinolone (8a) gave the respective 6-endo-cyclisation products in good yields. 4-(3,3-Dimethyl-4-iodobutyl)-quinolone (6b)
制备了六个带有ω-碘烷基链的4-取代的喹诺酮6-8,并使用BEt 3 / O 2作为引发剂,Bu 3 SnH或TMS 3 SiH作为氢化物源,进行还原性自由基环化条件。4-(4-碘丁基)-喹诺酮(6a)及4-(3-碘丙硫基)-喹诺酮(8A),得到相应的6-内-cyclisation产品的良好收益。4-(3,3-二甲基-4-碘丁基)-喹诺酮(6b)以5 exo方式环化,而其他底物仅递送还原产物。环化反应可在对映体过量(94-99%ee)高的手性模板(1)存在下进行。通过NMR滴定实验研究了底物6a与1的缔合行为。在6b的对映选择性环化中,当将产物ee与模板的ee进行比较时,观察到了明显的非线性。