The Cu(OTf)2- and Yb(OTf)3-catalyzed Claisen rearrangement of 2-alkoxycarbonyl-substituted allyl vinyl ethers

Organic Letters

Volumn 3, Issue 1, 2001, Pages 49-51

  Hiersemann, Martin ^a   Abraham, Lars ^a  

^a DRESDEN UNIVERSITY OF TECHNOLOGY   (Germany)

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ARTICLE;

EID: 0002446999     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol006760w     Document Type: Article

References (22)

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4. For an Al(III)-catalyzed Claisen rearrangement of an aliphatic allyl vinyl ether, see: Saito, S.; Shimada, K.; Yamamoto, H. Synlett 1996, 721.
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17. -2 mbar. Prior to use, they were stored at 200°C.
18. For the coordination of Cu(II)-species to α-thio acrylates, see ref 5i.
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20. (b) Demo, N. C.; Haddon, R. C.; Nowak, E. N. J. Am. Chem. Soc. 1970, 92, 6691.
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22. Assuming a concerted rearrangement, a boatlike transition state for the catalyzed Claisen rearrangement of Z,E-1a,c could also account for the formation of the syn-2a,c diastereomer. We found that the thermal Claisen rearrangement of Z,E-1a led to the exclusive formation of anti-2a whereas Z,Z-1a afforded syn-2a. Therefore, we conclude that the thermal rearrangement proceeds exclusively through chairlike transition states. To accept a boatlike transition state for the catalyzed Claisen rearrangement of Z,E-1a,c, it would be necessary to explain why the presence of Cu(II) or Yb-(III) opens access to a boatlike transition state at room temperature for the rearrangement of Z,E-1a,c. Further experiments to clarify the mechanism of the catalyzed Claisen rearrangement are currently underway.