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Synfacts 2008(8): 0840-0840  
DOI: 10.1055/s-2008-1077914
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of Fused Cyclobutanes via [2+2] Cationic Cycloadditions

Contributor(s): Mark Lautens, Frédéric Ménard
C. Ko, J. B. Feltenberger, S. K. Ghosh, R. P. Hsung*
University of Wisconsin, Madison, USA
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Publication History

Publication Date:
23 July 2008 (online)

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Significance

Four Lewis and Brønsted acids were found to be competent at mediating an intramolecular version of Gassman’s original cyclo­butane synthesis (Tetrahedron Lett. 1990, 31, 6489). The reaction was shown to proceed by stepwise formation of cationic intermediates, as monocyclic intermediates were isolated in some cases. The reaction could be made catalytic by using an iron salt as the Lewis acid. A synthetic application was demonstrated in the formal synthesis of natural product raikovenal and its epimer.