Construction of Tetracyclic 3-Spirooxindole through Cross-Dehydrogenation of Pyridinium: Applications in Facile Synthesis of (±)-Corynoxine and (±)-Corynoxine B
摘要:
A facile and straightforward method was developed to construct the fused tetracyclic 3-spirooxindole skeleton, which exists widely in natural products. The formation of the tetracyclic 3-spirooxindole structure was achieved through a transition-metal-free intramolecular cross-dehydrogenative coupling of pyridinium, which were formed in situ by the condensation of 3-(2-bromoethyl)indolin-2-one derivatives with 3-substituted pyridines. As examples of the application of this new methodology, two potentially medicinal natural products, (+/-)-corynoxine and (+/-)-corynoxine B, were efficiently synthesized in five scalable steps.
The present study reports an asymmetric organocatalytic cascade reaction of oxindole derivates with α,β-unsaturated aldehydes efficiently catalyzed by simple chiralsecondaryamine. Spirooxindole-fused cyclopentanes were produced in excellent isolated yields (up to 98%) with excellent enantiopurities (up to 99% ee) and moderate to high diastereoselectivities. The synthetic utility of the protocol was
An Organocatalytic Cascade Strategy for the Enantioselective Construction of Spirocyclopentane Bioxindoles Containing Three Contiguous Stereocenters and Two Spiro Quaternary Centers
作者:Wangsheng Sun、Gongming Zhu、Chongyang Wu、Liang Hong、Rui Wang
DOI:10.1002/chem.201200478
日期:2012.5.29
A rapid and efficient organocatalyticcascade sequence for the direct construction of spirocyclopentanebioxindoles has been carried out by using a chiral squaramide catalyst in the presence of a base. This process constitutes a powerful approach to the preparation of biologically important bispirooxindoles in high enantioselectivities (see scheme).
A collective formal synthesis approach to bioactive oxindole alkaloids, including (±)-rhynchophylline, (±)-isorhynchophylline, (±)-mitraphylline, (±)-formosanine, (±)-isomitraphylline, and (±)-isoformosanine, is completed in a protecting-group free manner. Besides multigram-scaled operations, the notable feature of the synthesis is the application of two one-pot, sequential transformations. Namely
Photochemical Deracemization of 3‐Substituted Oxindoles
作者:Johannes Großkopf、Alexandra A. Heidecker、Thorsten Bach
DOI:10.1002/anie.202305274
日期:2023.7.24
A benzophenone-based catalyst was used as the only source of chirality in the photochemical deracemization of 3-substituted oxindoles. The reaction likely proceeds by hydrogen atom transfer and delivers the desired products, and derivatives thereof, with high enantiomeric excess.