Catalytic and highly enantioselective Friedel–Crafts type reactions of heteroaromatic compounds with trifluoropyruvate and glyoxylate by a dicationic palladium complex

Abstract

Scheme 1. Regio-and enantioselective Friedel-Crafts type reactions with dicationic palladium catalyst 2. Results and discussion Initially, the Friedel-Crafts type reaction of 2-trimethylsilyl furan 4a as a nucleophile was examined in the presence of

Lewis Acid Catalyzed Friedel–Crafts Alkylation of Alkenes with Trifluoropyruvates

“…19 (S,E)-Ethyl 2-Hydroxy-4-phenyl-2-(trifluoromethyl)but-3-enoate (3ba). 14 Purified by chromatography on silica gel, eluting with ethyl acetate/petroleum ether 1:10 (v/v); yellow oil, 40.4 mg, 74% yield; 1 H NMR (500 MHz, CDCl 3 ): δ 7.43−7.49 (m, 2H), 7.37 (t, J = 8.0 Hz, 2H), 7.32 (t, J = 7.5 Hz, 1H), 7.13 (d, J = 15.5 Hz, 1H), 6.38 (d, J = 15.5 Hz, 1H), 4.42 (m, 2H), 4.15 (s, 1H), 1.39 (t, J = 7.0 Hz, 3H).…”

Enantioselective Friedel–Crafts Reaction of Heteroaromatic Compounds with Glyoxals Catalyzed by Chiral Oxazaborolidinium Ion Catalyst

“…One of the most effective strategies for the formation of carbon–carbon bonds is the catalytic Friedel–Crafts reaction . Enantioselective catalytic Friedel–Crafts reactions of aromatic and heteroaromatic compounds with carbonyl compounds or imines have received considerable attention due to their ability to generate stereocenters at the benzylic position . Among the carbonyl reactant, a novel approach using the activated aldehyde glyoxal in the enantioselective Friedel–Crafts reaction has been proposed as a method to produce chiral α-hydroxyketones .…”

Enantioselective Friedel–Crafts Alkylation of Furans with o-Quinone Methide Using a Chiral Oxazaborolidinium Ion Catalyst

“…Among the catalytic asymmetric alkylations of aromatic and heteroaromatic compounds, reports with regard to the use of furans (especially unsubstituted furan) remain rare, presumably because of its low nucleophilicity, polyalkylation, and the relative instability of furans toward acidic conditions. , Furans are widely found in biologically active natural products, medicinal agents, and a number of intermediates in multistep syntheses. , Moreover, furans are regarded as important platform chemicals in biorefinery development . To the best of our knowledge, only one successful example of Friedel–Crafts alkylation of an unsubstituted furan was reported with trifluoropyruvate, whereas the catalytic Friedel–Crafts alkylations of electron-rich arenes, , indoles, , and pyrroles , with a variety of electrophiles are well-documented.…”

“…When the reaction was carried out at −78 °C in the presence of 3 Å molecular sieves, the desired 2-substituted furan 2a was formed in 38% yield with 87% ee (entry 1). At the same time, 2,5-disubstituted furan 4a was isolated as a mixture of C 2 -symmetric and meso adducts in 43% yield with 78:22 selectivity for the C 2 isomer. , Since the nucleophilicity of alkyl-substituted furan 2a was greater than that of unsubstituted furan, the amount of furan was increased to 10.0 equiv to suppress the dialkylation pathway, and 2a was obtained in an enhanced yield of 78% with 91% ee (entry 2). To further improve the yield, the catalyst structure was modified with triflic imide-activated catalyst 3c (with a 2,3-dimethylphenyl substituent), yielding the desired product in a high yield of 85% but with a diminished 89% ee (entries 2–4).…”