A stereochemically flexible approach to pyrrolidines based on 5-endo-trig iodocyclisations of homoallylic sulfonamides
作者:Andrew D. Jones、David W. Knight、David E. Hibbs
DOI:10.1039/b008537p
日期:——
5-endo-trig Iodocyclisations of the (E)-homoallylic sulfonamides 24 in the presence of potassium carbonate give excellent yields of trans-2,5-disubstituted-3-iodopyrrolidines 36. In the absence of base, these initial kinetic products undergo rapid isomerization to the corresponding cis-2,5-disubstituted pyrrolidines 37 by a ring opening–reclosure mechanism to these thermodynamic isomers. Octahydroindole derivatives 40 and 41 can be similarly obtained from the alk-2-enylcyclohexylsulfonamides 31 and 32. Attempted 5-endo-trig cyclisations of homoallylic carbamates were generally unsuccessful and resulted instead in
relatively inefficient 6-exo cyclisations involving the carbamate carbonyl group. Deiodination provides both trans- and cis-2,5-disubstituted pyrrolidines [49 and 50]; the free amine derived from trans-2-butyl-5-pentylpyrrolidine 49d is a component of a fire ant defence pheromone. X-Ray crystallography was carried out for 37f, 36, and 37k.
在碳酸钾存在下,(E)-高烯丙基磺酰胺24的5-endo-trig碘环化反应能够高产率地得到反式-2,5-二取代-3-碘吡咯烷36。在没有碱的情况下,这些初始动力学产物通过开环-重闭环机制迅速异构化为相应的顺式-2,5-二取代吡咯烷37,转变为这些热力学异构体。八氢吲哚衍生物40和41也可以从烯丙基环己基磺酰胺31和32得到。高烯丙基氨基甲酸酯的5-endo-trig环化反应尝试一般都不成功,反而导致了氨基甲酸酯羰基参与的相对低效的6-exo环化反应。脱碘反应可以得到反式和顺式-2,5-二取代吡咯烷[49和50];来源于反式-2-丁基-5-戊基吡咯烷49d的游离胺是火蚁防御信息素的一个组成部分。对37f、36和37k进行了X射线晶体学分析。