Abstract
Expansion of the scope of the 1,3-diaza-Claisen rearrangement beyond bridged-bicyclic tertiary allylic amines has been investigated through a tethering strategy. Isothioureas tethered to tertiary allylic amines are converted to carbodiimides through a reaction with AgOTf/Et3N. Intramolecular cyclization of the tertiary allylic amine to the carbodiimide equilibrates with a zwitterionic intermediate. Heating the carbodiimide/zwitterion affords a rearrangement product. Heating carbodiimide/zwitterion with a deuterated allyl group results in the scrambling of the deuterium label, which is consistent with an ionic mechanism involving heterolytic cleavage of the allylic C-N bond, followed by trapping of the allyl cation at either terminal carbon. The ionic mechanism is attributed to silver salt contamination since pushing deuterium-labeled carbodiimide/zwitterion through silica gel prior to heating results in clean deuterium transposition consistent with a sigmatropic mechanism, and adding back silver salts results in deuterium scrambling. Overall, the tethering strategy broadens the scope of the rearrangement to simpler allylic substrates. Density functional theory (DFT) calculations of the sigmatropic rearrangement are in agreement with reactivity trends observed with reactions run under silver-free conditions.
Original language | English (US) |
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Pages (from-to) | 8197-8215 |
Number of pages | 19 |
Journal | Journal of Organic Chemistry |
Volume | 86 |
Issue number | 12 |
DOIs | |
State | Published - Jun 18 2021 |
Externally published | Yes |
Bibliographical note
Funding Information:Funding for this project was provided by grant CHE-1111694 from the NSF. Computations were performed on the Vermont Advanced Computing Core.
Publisher Copyright:
© 2021 American Chemical Society.
PubMed: MeSH publication types
- Journal Article
- Research Support, U.S. Gov't, Non-P.H.S.