Tandem Inter [4 + 2]/Intra [3 + 2] Cycloadditions of Nitroalkenes. Asymmetric Synthesis of Highly Functionalized Aminocyclopentanes Using the Bridged Mode (β-Tether) Process
作者:Scott E. Denmark、Julie A. Dixon
DOI:10.1021/jo9802170
日期:1998.9.1
An asymmetric, tandem inter [4 + 2]/intra [3 + 2] bridged mode (beta-tether) cycloaddition of nitroalkenes has been developed. This new sequence involves the Lewis acid-promoted [4 + 2] cycloaddition of nitro olefins with enantiopure 1-alkoxy-1,4-dienes. The resulting nitronates, bearing a C(5) tethered dipolarophile, undergo thermal, intramolecular [3 + 2] cycloaddition to afford stable tricyclic
已经开发了不对称的,串联的[4 + 2] /内部[3 + 2]桥联式(β-系链)硝基烯烃加成环。这一新序列涉及路易斯烯酸与对映体纯的1-烷氧基-1,4-二烯的路易斯烯烃促进的[4 + 2]环加成反应。生成的带有C(5)拴住的双极性亲子的硝酸盐经历分子内热[3 + 2]环加成反应,得到稳定的三环亚硝基缩醛,随后可将其还原成有趣的氨基环戊烷。因此,通过三个步骤,可以以高收率和高ee构建高度官能化,对映异构体富集的氨基环戊烷。此外,发现路易斯酸对[4 + 2]环加成反应的立体化学结果具有显着影响。