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DOI: 10.1055/s-0034-1378507
Adjacent All-Carbon Quaternary Stereocenters via Nazarov Cyclization
Publication History
Publication Date:
18 July 2014 (online)
Significance
The authors developed an asymmetric Nazarov electrocyclization, which provides cyclopentenones with adjacent all-carbon quaternary stereocenters in moderate to good yields and excellent enantioselectivities, using a BINOL-derived N-triflyl phosphoramide catalyst. The current paper is an extension to the authors’ previous work on a non-enantioselective version of triflimide-catalyzed Nazarov electrocyclization (Angew. Chem. Int. Ed. 2013, 52, 11102).
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Comment
The Nazarov electrocyclization is a useful method to construct highly functionalized cyclopentenones, which are important scaffolds in natural products. Most of the reported asymmetric versions are limited to either α-ester- or β-aryl-substituted dienones, since these functional groups strongly polarize the substrates accelerating the Nazarov cyclization. In their current work, the authors achieved the Nazarov electrocyclization of substrates with aliphatic groups in β-position. The 4π-electron conrotatory cyclization of the pentadienyl cation is asymmetrically directed by the chiral anion. It should be emphasized that this method provides a new way for chemists to synthesize adjacent quaternary stereocenters in high enantioselectivities.
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