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. 2006 Feb 8;128(5):1472-3.
doi: 10.1021/ja058222q.

Umpolung of Michael acceptors catalyzed by N-heterocyclic carbenes

Christian Fischer  1 , Sean W Smith, David A Powell, Gregory C Fu
Affiliations

Umpolung of Michael acceptors catalyzed by N-heterocyclic carbenes

Christian Fischer et al. J Am Chem Soc. .

Abstract

N-Heterocyclic carbenes can catalyze beta-alkylations of a range of alpha,beta-unsaturated esters, amides, and nitriles that bear pendant leaving groups to form a variety of ring sizes. In this process, the nucleophilic catalyst transiently transforms the normally electrophilic beta carbon into a nucleophilic site through an unanticipated addition-tautomerization sequence.

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Figures

Figure 1
Figure 1
Possible mechanism for carbene-catalyzed β-alkylations of Michael acceptors.
See this image and copyright information in PMC

References

    1. For leading references, see: Powell DA, Maki T, Fu GC. J. Am. Chem. Soc. 2005;127:510–511.

    1. For overviews of processes catalyzed by nucleophilic carbenes, see: Zeitler K. Angew. Chem., Int. Ed. 2005;44:7506–7510. Nair V, Bindu S, Sreekumar V. Angew. Chem., Int. Ed. 2004;43:5130–5135.

    1. For a review of processes catalyzed by nucleophilic phosphines, see: Methot JL, Roush WR. Adv. Synth. Catal. 2004;346:1035–1050.

    1. For precedent in a more highly activated substrate, see: Enders D, Breuer K, Teles JH, Ebel KJ. Prakt. Chem. 1997;339:397–399.

    1. Seebach D. Angew. Chem., Int. Ed. Engl. 1979;18:239–258.
    2. Hase TA, editor. Umpoled Synthons. Wiley; New York: 1987.

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