91902-68-0Relevant academic research and scientific papers
Remote enantioselective friedel-crafts alkylations of furans through HOMO activation
Li, Jun-Long,Yue, Cai-Zhen,Chen, Peng-Qiao,Xiao, You-Cai,Chen, Ying-Chun
supporting information, p. 5449 - 5452 (2014/06/09)
Catalytic asymmetric Friedel-Crafts alkylation 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 trienamine species using a chiral primary amine. Exclusive regioselective alkylation at the 5-position occurred with alkylidenemalononitriles, and high reactivity and excellent enantioselectivity (up to 95 % ee) was obtained by this remote activation. Alternative strategy: An asymmetric and regioselective Friedel-Crafts alkylation reaction of 2-furfuryl ketones and alkylidenemalononitriles was developed and involves the in situ generation of a formal HOMO-raised trienamine species. A diversity of alkylation products were produced in moderate to excellent enantioselectivity under the catalysis of a chiral bifunctional primary amine-thiourea (1).
