Rozsar D, Formica M, Yamazaki K, Hamlin TA, Dixon DJ. Bifunctional Iminophosphorane-Catalyzed Enantioselective Sulfa-Michael Addition to Unactivated α,β-Unsaturated Amides.
J Am Chem Soc 2022;
144:1006-1015. [PMID:
34990142 PMCID:
PMC8793149 DOI:
10.1021/jacs.1c11898]
[Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
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The
first metal-free catalytic intermolecular enantioselective
Michael addition to unactivated α,β-unsaturated amides
is described. Consistently high enantiomeric excesses and yields were
obtained over a wide range of alkyl thiol pronucleophiles and electrophiles
under mild reaction conditions, enabled by a novel squaramide-based
bifunctional iminophosphorane catalyst. Low catalyst loadings (2.0
mol %) were achieved on a decagram scale, demonstrating the scalability
of the reaction. Computational analysis revealed the origin of the
high enantiofacial selectivity via analysis of relevant transition
structures and provided substantial support for specific noncovalent
activation of the carbonyl group of the α,β-unsaturated
amide by the catalyst.
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