Klein Johannes E M N, Müller-Bunz Helge, Evans Paul
Centre for Synthesis and Chemical Biology, School of Chemistry and Chemical Biology, University College Dublin, Dublin 4, Ireland.
Org Biomol Chem. 2009 Mar 7;7(5):986-95. doi: 10.1039/b819610a. Epub 2009 Jan 23.
The bromination of a series of cyclohexenyl substituted secondary amines 1a-i has been investigated using Br2, PHT and NBS. In the case of Br2 and NBS the secondary amines preferentially undergo N-bromination. In contrast, PHT cleanly affords the products of alkene dibromination. In the case ofBr2 the N-bromo species then give the products of alkene dibromination, albeit less efficiently. On subsequent treatment with K2CO3 these dibromides form the corresponding hexahydroindoles 2a-h and octahydroquinoline 2i. The presence of an N-substituent bearing a stereogenic centre (1h and 1i) was studied and the products 2h and 2i were isolated with no diastereoselectivity. When NBS was used a novel cyclisation, forming bromo-substituted octahydroindoles 9a,b and d, was observed. In relation to this sequence it was shown that these products were not intermediates in the former Br2/PHT processes and that the reaction only proceeded in the presence of the succinimide by-product of N-bromination.
使用Br₂、PHT和NBS研究了一系列环己烯基取代的仲胺1a - i的溴化反应。在Br₂和NBS的情况下，仲胺优先发生N - 溴化反应。相比之下，PHT能顺利得到烯烃二溴化产物。在Br₂的情况下，N - 溴代物种随后生成烯烃二溴化产物，尽管效率较低。在用K₂CO₃后续处理时，这些二溴化物形成相应的六氢吲哚2a - h和八氢喹啉2i。研究了带有手性中心的N - 取代基（1h和1i）的存在情况，分离得到的产物2h和2i没有非对映选择性。当使用NBS时，观察到一种新型环化反应，形成溴代八氢吲哚9a、b和d。关于这个反应序列，结果表明这些产物不是之前Br₂/PHT反应过程中的中间体，并且该反应仅在N - 溴化反应的琥珀酰亚胺副产物存在下进行。
