6´-Aminocinchonidine (CAS-No. 2143936-34-7) is a new member of the Cinchona Alkaloid family. The additional primary...
Buchler Glossary
Friedel-Crafts reactions in organic chemistry are referred to two main types of reactions, known as alkylation reactions and acylation reactions. Friedel-Crafts reactions are frequently employed to attach substituents to an aromatic ring. The Friedel-Crafts alkylation (FCA) reaction is one of the most straightforward approaches to the functionalization of aromatic compounds and the introduction of benzylic carbon stereocenters.
Asymmetric Friedel-Crafts-Alkylation
In particularly Cinchona Alkaloid based organocatalysts are widely used to establish the benzylic chiral center. These metal-free organic catalysts offers an economical, less toxic and environmentally friendly alternative to other catalytic systems.
α,β-unsaturated ketones as well as α,β-unsaturated aldehydes are for instance suitable electrophiles for the FCA-type Michael addition of N-unsubstituted pyrroles or indoles using 9-Epiamino Cinchona alkaloid catalysts. The corresponding addition products can be obtained in good to excellent yields and with high enantioselectivity.
On the other hand highly asymmetric aza-Friedel–Crafts (aza-F-C) reaction of cyclic trifluoromethyl ketimines and naphthols/phenols can be obtained with up to 99% yields and up to 99% ee’s using Quinine-squaramide as a catalyst. Also Cinchona alkaloid-urea bifunctional organocatalysts are often applied to synthesize a broad range of Friedel-Crafts adducts with high enantioselectivities. Similarly Cinchona based bifunctional thiourea organocatalysts enable the aza-Friedel–Crafts reaction of 1-naphthol with isatin derived N-Boc ketimines.
A further asymmetric aza-Friedel–Crafts reaction of naphthols with N-sulfonyl imines can be reviewed in our free of charge chiral catalyst search data Base. The cupreine-derived bifunctional organocatalyst BzCPN efficiently catalyzes the formation of aza-Friedel–Crafts products in good to excellent yields (up to 99 %) with high enantioselectivities (up to 99.5:0.5 er) under mild reaction conditions, with a low catalyst loading (2–5 mol-%), and in an aerobic environment.
You will find a lot of asymmetric Friedel-Crafts reactions in our free of charge Chiral Catalyst Search Data Base.
Example from Literature
The origin for highly enantioselective induction of 1-naphthol to isatin-derived N-Boc ketimines catalyzed by quinine thiourea catalyst: an experimental and computational study. (Barik et al.; RSC Adv. 2015, 5, 69493–69501.)
Further Articles:
6´-Aminodihydrocinchonidine (CAS-No. 107781-90-8)
6´-Aminodihydrocinchonidine Base (CAS-No. 107781-90-8) is a cinchona alkaloid closely related to 6´-Aminocinchonidine....
6´-Aminodihydrocinchonine (CAS-No. 911708-35-5)
6´-Aminodihydrocinchonine Base (CAS-No. 911708-35-5) is a cinchona alkaloid closely related to 6´-Aminocinchonine....
Alkynylation
Alkynylation is an addition reaction in organic synthesis where a terminal alkyne adds to a carbonyl group to form an...
Allylsilylations
Allylsilylations are performed between allylsilanes and aldehydes furnishes homo allyl alcohols. Using Cinchona...
Aminohydroxylation
The Sharpless Aminohydroxylation allows the syn-selective preparation of 1,2-amino alcohols by reaction of alkenes...