Remote enantioselective Friedel-Crafts alkylations of furans through HOMO activation
Jun-Long Li1, Cai-Zhen Yue, Peng-Qiao Chen
1Key Laboratory of Drug-Targeting and Drug Delivery System of the Ministry of Education, West China School of Pharmacy, and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041 (China).
Abstract:
Catalytic asymmetric Friedel-Crafts alkylation is a powerful protocol for constructing a chiral C(sp(2))-C(sp(3)) 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.
Related Concept Videos
Limitations of Friedel–Crafts Reactions
Electrophilic Aromatic Substitution: Friedel–Crafts Alkylation of Benzene
Electrophilic Aromatic Substitution: Friedel–Crafts Acylation of Benzene
Amines to Alkenes: Hofmann Elimination
Under thermal conditions, the hydroxide can abstract a proton from the β carbon; this generates an alkene with the simultaneous...
Radical Anti-Markovnikov Addition to Alkenes: Overview
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...


