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DOI: 10.1055/s-2007-968730
Enantioselective Conjugate Addition of Indoles to Enones
Contributor(s):Mark Lautens, Frédéric MénardKorea Advanced Institute of Science and Technology, Daejeon, Korea
Catalytic Enantioselective Friedel-Crafts Alkylations of Indoles with α′-Phosphoric Enones
Org. Lett. 2007, 9: 2281-2284
Publication History
Publication Date:
24 July 2007 (online)
Key words
conjugate addition - copper(II) - BOX ligand - β-ketophosphonates
Significance
The report illustrates another example of the versatile catalytic activity of the Cu(II)(BOX) system. The Michael addition of indoles to various α,β-unsaturated ketones yielded enantioenriched β-keto phosphonates 3, which can be further derivatized. The β-keto phosphonate in 2 provides two-point binding to the copper metal center.
Comment
The enantioenriched keto phosphonates were shown to be precursors to methyl ketone 4 via reduction, or to a new α,β-unsaturated ketone 5. The reaction was slow for hindered Michael acceptors (i.e. 20 days for 3f), but still furnished the desired products in high yield and enantioselectivity. The authors did not report the absolute stereochemistry of the products obtained. It would be interesting to see if systems like 5 would allow further catalyst-controlled reactions.