A new method for the synthesis of the octahydropyrrolo[3,2,1-ij]quinoline ringsystem that possesses the characteristic skeleton of the aspidosperma family of alkaloids has been developed. The method utilizes an intramolecularDiels−Alderreaction of an amido-substituted furan across a tethered indole π-bond. To apply this strategy to the synthesis of the indole alkaloid spegazzinidine, it was necessary
已开发出一种新的合成八氢吡咯并[3,2,1- ij ]喹啉环系统的方法,该系统具有生物碱的精孢子家族的特征骨架。该方法利用酰胺基取代的呋喃的分子间Diels-Alder反应穿过拴系的吲哚π键。为了将该策略应用于吲哚生物碱spegazzinidine的合成,有必要解决组装五环骨架的最终D-环的问题。发现N-烯丙基-7-溴-3a-甲基六氢吲哚满酮系统的自由基环化优先导致6-内-trig环化产物,在高稀释条件下可获得最佳收率。六元环化产物通过两个反应路径生成:(a)6-内-trig闭环和(b)重排通过5 -exo-trig环化获得的中间体亚甲基-环戊基。制备了许多含有束缚的烯基的相关的7-溴取代的六氢吲哚酮,发现它们在自由基和钯介导的反应条件下均能有效地环化。用几个N-丁烯基取代的系统进行乙烯基自由基环化,得到6- exo和7- end环化产物的混合物。将乙基取代基引入C的方案还开发了20个位置
Six- versus Five-Membered Ring Formation in Radical Cyclizations of 7-Bromo-Substituted Hexahydroindolinones
[reaction: see text] Radical cyclization of N-allyl-7-bromo-3a-methyl-hexahydroindol-2-one affords a six-membered ring product that prevails over the isomeric five-membered compound. The former product is generated through two reaction pathways: (a) 6-endo-trig ringclosure and (b) rearrangement of an intermediate methylenecyclopentyl radical obtained by 5-exo-trig cyclization.