Synfacts 2016; 12(07): 0739
DOI: 10.1055/s-0035-1562255
Organo- and Biocatalysis
© Georg Thieme Verlag Stuttgart · New York

Enantioselective Formation of Quaternary Carbons by Radical Conjugated Addition

Contributor(s): Benjamin List, Francesca Mandrelli
Murphy JJ, Bastida D, Paria S, Fagnoni M, Melchiorre P * Barcelona Institute of Science and Technology, Tarragona and Catalan Institution for Research and Advanced Studies, Barcelona, Spain; University of Pavia, Italy
Asymmetric Catalytic Formation of Quaternary Carbons by Iminium Ion Trapping of Radicals.

Nature 2016;
532: 218-222
Further Information

Publication History

Publication Date:
17 June 2016 (online)

 
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Significance

Melchiorre and co-workers report the first example of a radical conjugated addition to β,β-disubstituted cyclic enones by a combination of photoredox and asymmetric organocatalysis to give quaternary stereocenters with high enantioselectivity. This method exploits iminium ion catalysis, previously applied only in polar chemistry, within the field of radical reactivity.


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Comment

The chiral organocatalyst has been elegantly designed with a redox-active carbazole moiety that drives the formation of the iminium ion I. This reaction is followed by stereoselective trapping of the photochemically generated, carbon-centered radical R•. The new radical species II leads, through an electron-relay mechanism, to III and, after tautomerization and reduction, the product is formed with high enantioselectivity.


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