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Synfacts 2017; 13(03): 0267
DOI: 10.1055/s-0036-1590060
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart · New York

Asymmetric Radical Cyclopropanation of Alkenes

Contributor(s):
Mark Lautens
,
Ivan Franzoni
Wang Y. Wen X. Cui X. Wojtas L. Zhang XP. * Boston College, Chestnut Hill and University of South Florida, Tampa, USA
Asymmetric Radical Cyclopropanation of Alkenes with In Situ-Generated Donor-Substituted Diazo Reagents via Co(II)-Based Metalloradical Catalysis.

J. Am. Chem. Soc. 2017;
139: 1049-1052
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Publication History

Publication Date:
15 February 2017 (online)

 
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Key words

cobalt catalysis - asymmetric radical reaction - cyclopropanation - diazo reagents

Significance

The use of cobalt(II) complexes with chiral amidoporphyrins has emerged as a powerful approach to asymmetric radical transformations. Zhang and co-workers report the use of a chiral cobalt catalyst in the asymmetric radical cyclopropanation of alkenes with diazo reagents to generate enantioenriched substituted cyclopropanes.


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Comment

Diazo reagents, generated in situ from sulfonyl hydrazones under basic conditions, reacted with terminal mono- and disubstituted alkenes to form the corresponding cyclopropane products in good yields and diastereoselectivities, and with excellent enantioselectivities. Mechanistic experiments support a stepwise radical mechanism in which the cobalt complex first reacts with the diazo reagent to form a cobalt(III) benzyl radical followed by radical addition of the alkene.


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