Chemoselective Switch in the Asymmetric Organocatalysis of 5H-Oxazol-4-ones and N-Itaconimides: Addition-Protonation or [4+2] Cycloaddition
Date
2016-01-22
Authors
Zhu, Bo
Lee, Richmond
Li, Jiangtao
Ye, Xinyi
Hong, San-Ni
Qiu, Shuai
Coote, Michelle
Jiang, Zhiyong
Journal Title
Journal ISSN
Volume Title
Publisher
Wiley
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.
Description
Keywords
chemoselectivity, chirality, density functional calculations, organocatalysis, synthetic methods
Citation
Collections
Source
Angewandte Chemie (International ed. in English)
Type
Journal article
Book Title
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Access Statement
Open Access