Enantioselective Synthesis of Allenes by Catalytic Traceless Petasis Reactions
Yao Jiang, Abdallah B. Diagne, Regan J. Thomson* and Scott E. Schaus*
*Department of Chemistry, Northwestern University, Evanston, Illinois 60208; Department of Chemistry, Boston University, Boston, Massachusetts 02215, United States, Email: r-thomsonnorthwestern.edu, seschausbu.edu
Y. Jiang, A. B. Diagne, R. J. Thomson, S. E. Schaus, J. Am. Chem. Soc., 2017, 139, 1826-1829.
DOI: 10.1021/jacs.6b11937 (free Supporting Information)
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An asymmetric boronate addition to sulfonyl hydrazones catalyzed by chiral biphenols provides enantioenriched allenes in a traceless Petasis reaction. The resulting Mannich product from nucleophilic addition eliminates sulfinic acid, yielding a propargylic diazene that performs an alkyne walk to afford the allene. Two enantioselective approaches have been developed for the synthesis of allylic hydroxyl allenes and 1,3-alkenyl allenes.
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Development of an enantioselective allene synthesis reaction. Asymmetric routes to chiral allenes from (A) alkynyl boronate addition to glycolaldehyde imine and (B) allylation of alkynyl hydrazones.
D. A. Mundal, K. E. Lutz, R. J. Thomson, J. Am. Chem. Soc., 2012, 134, 5782-5785.