Synfacts 2014; 10(2): 0155
DOI: 10.1055/s-0033-1340583
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart · New York

Asymmetric Allylic Alkylation of Acyclic β‑Keto Esters Catalyzed by Iridium

Contributor(s): Mark Lautens, Marcel Sickert
Liu W.-B, Reeves CM, Stoltz BM * California Institute of Technology, Pasadena, USA
Enantio‑, Diastereo‑, and Regioselective Iridium-Catalyzed Asymmetric Allylic Alkylation of Acyclic β-Ketoesters.

J. Am. Chem. Soc. 2013;
135: 17298-17301
Further Information

Publication History

Publication Date:
20 January 2014 (online)

 

Significance

The asymmetric allylic alkylation belongs to one of the fundamental C–C bond-­formation reactions and a variety of nucleophiles are successfully employed. However, the formation of an all-carbon quaternary stereocenter is still a challenging case. Herein, the authors report an efficient allylic alkylation of acyclic β-keto esters catalyzed by an Ir–N-aryl-phosphoramidite catalyst. The products bearing vicinal quaternary and tertiary stereocenters are obtained in high yield, regio-, diastereo-, and almost perfect enantio­selectivity.


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Comment

The substrate scope of the iridium-catalyzed diastereoselective allylic alkylation covers aryl, heteroaryl and alkenyl substituents on the allyl carbonate electrophile. Interestingly, the regio­selective outcome of the reaction (branched vs. linear) is influenced by the substituent’s ability to donate or withdraw electron density. In the case of 4-MeOAr, the branched product is formed almost exclusively. Variations on the β-keto ester moiety are also conducted and a variety of functional groups are tolerated at the α position (R2), including alkyl, allyl, propargyl, and heteroaryl groups.


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