Chemoselective Switch in the Asymmetric Organocatalysis of 5H-Oxazol-4-ones and N-Itaconimides: Addition-Protonation or [4+2] Cycloaddition

Bo Zhu, Richmond Lee, Jiangtao Li, Xinyi Ye, San-Ni Hong, Shuai Qiu, Michelle L. Coote, Zhiyong Jiang

Research output: Contribution to journalArticlepeer-review

55 Citations (Scopus)

Abstract

We report a synthetic strategy for a chemoselective switch and a diastereo-divergent approach for the asymmetric reaction of 5H-oxazol-4-ones and N-itaconimides catalyzed by l-tert-leucine-derived tertiary amine-urea compounds. The reaction was modulated to harness either tandem conjugate addition-protonation or [4+2] cycloaddition as major product with excellent enantio- and diastereoselectivities. Subjecting the enantio-enriched cycloaddition products to a basic silica gel reagent yields the diastereomer vis-à-vis the product directly obtained under conditions for addition-protonation, thus opening a diastereo-divergent route for creating 1,3-tertiary-hetero-quaternary stereocenters. Quantum chemical studies further provide stereochemical analysis for the [4+2] process and a plausible mechanism for this chemoselective switch is proposed.

Original languageEnglish
Pages (from-to)1299-1303
Number of pages5
JournalAngewandte Chemie - International Edition
Volume55
Issue number4
DOIs
Publication statusPublished - 22 Jan 2016
Externally publishedYes

Keywords

  • chemoselectivity
  • chirality
  • density functional calculations
  • organocatalysis
  • synthetic methods

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