Enantioselective Synthesis of α,α-Disubstituted Cyclopentenes by an N-Heterocyclic Carbene-Catalyzed Desymmetrization of 1,3-Diketones
Manabu Wadamoto, Eric M. Phillips, Troy E. Reynolds and Karl A. Scheidt*
*Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, Email: scheidtnorthwestern.edu
M. Wadamoto, E. M. Philipps, T. E. Reynolds, K. A. Scheidt, J. Am. Chem. Soc., 2007, 129, 10098-10099.
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An enantioselective synthesis of α,α-disubstituted cyclopentenes proceeds via a chiral enol generated in situ from an α,β-unsaturated aldehyde and a chiral N-heterocyclic carbene catalyst. This reactive enol undergoes addition to one of two enantiotopic ketones to afford an optically active β-lactone. Depending on the substitution, a decarboxylation produces the cyclopentene products in high ee.
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proposed reaction pathway