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Synfacts 2005(0): 0049-0049  
DOI: 10.1055/s-2005-869939
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart · New York

Enantioselective Enol Lactone Synthesis under Double Catalytic Conditions

Contributor(s): Mark Lautens, Josephine Yuen
K. Itoh, M. Hasegawa, J. Tanaka, S. Kanemasa*
Kyushu University, Japan
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Publication History

Publication Date:
20 July 2005 (online)

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Significance

Under the ‘double-catalytic condition’ protocol using the (R,R)-DBFOX/Ph complex of nickel(II) perchlorate hexahydrate and tetra­methyl-piperidine, enol lactones were formed with high enantioselectivity. The mechanism proceeds via an enantioselective Michael addition followed by enolization of the diketone moiety, then cyclization with concomitant displacement of the pyrazole auxiliary. Catalyst loadings can be reduced to 2 mol% and use of β-hydroxy-lactones instead of the diketone is also reported.