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DOI: 10.1055/s-0036-1590060
Asymmetric Radical Cyclopropanation of Alkenes
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
Publikationsverlauf
Publikationsdatum:
15. Februar 2017 (online)
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.
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.