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Synfacts 2009(5): 0560-0560  
DOI: 10.1055/s-0029-1216576
Organo- and Biocatalysis
© Georg Thieme Verlag Stuttgart ˙ New York

Highly Enantioselective Two-Step Organo-catalytic Cyclopropanation

Contributor(s): Benjamin List, Olga Lifchits
Y.-n. Xuan, S.-z. Nie, L.-t. Dong, J.-m. Zhang, M. Yan*
Sun Yat-sen University, Guangzhou, P. R. of China
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Publikationsdatum:
22. April 2009 (online)

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Significance

Yan and co-workers report an enantioselective organocatalytic approach to ­construct tetrasubstituted electrophilic cyclopropanes. The overall transformation requires two synthetic steps and consists of an organocatalytic Michael addition followed by a base-catalyzed intramolecular cyclization. Enantioselectivity is set in the first step using the cinchona alkaloid derivative 1 as the organocatalyst. Subsequent diastereo­selective ring closure using DABCO affords the cyclopropane products in moderate to good overall yields and excellent enantio- and diastereo­selectivity. Only aromatic Michael acceptors were reactive in the cyclopropanation.