Catalytic asymmetric Friedel–Craftsalkylation is a powerful protocol for constructing a chiral C(sp2)C(sp3) bond. Most previous examples rely on LUMO activation of the electrophiles using chiral catalysts with subsequent attack by electron‐rich arenes. Presented herein is an alternative strategy in which the HOMO of the aromatic π system of 2‐furfuryl ketones is raised through the formation of a formal
Construction of Furan Derivatives with a Trifluoromethyl Stereogenic Center: Enantioselective Friedel–Crafts Alkylations via Formal Trienamine Catalysis
作者:Guang-Jun Yang、Wei Du、Ying-Chun Chen
DOI:10.1021/acs.joc.6b01950
日期:2016.10.21
An asymmetric Friedel–Crafts alkylation reaction of 2-furfuryl ketones with β-trifluoromethyl enones has been developed via formal trienamine catalysis of a bifunctional primary amine-thiourea substance derived from L-tert-leucine, delivering the furanderivatives incorporating a stereogenic trifluoromethyl (CF3) group in good to high yields with excellent enantioselectivity.
A highly chemo- and regioselective Friedel–Craftsalkylation reaction of furans and thiophenes has been developed, which relies on the activation from the remote conjugated Mukaiyama silyl enol ether motif. Excellent enantioslectivity is generally obtained in reactions with α,β-unsaturated aldehydes under the well-established iminium ion catalysis of a chiral secondary amine.