Highly selective catalytic Friedel–Crafts sulfonylation of aromatic compounds using a FeCl3-based ionic liquid

Friedel–Crafts sulfonylation of aromatic compounds was carried out using FeCl₃-based ionic liquid. These liquids serve as efficient media as well as Lewis acid catalyst.     

BF3·OEt2-promoted reaction of isocyanides with o-aminobenzophenones

Aliphatic isocyanides react with o-aminobenzophenones in dichloromethane under Lewis acid catalysis at ambient temperature to give, unexpectedly, 4-aryl-4-hydroxy-3,4-dihydroquinazolines in good to excellent yields. The outcome of the reaction is rationalized by a skeletal rearrangement of the initially formed ‘intramolecular Passerini’ reaction products, 2-amino-3-hydroxy-3-aryl-3H-indoles.     

BF3·OEt2-catalyzed intermolecular reactions of arylmethylenecyclopropanes with (E)-1,1,3-triarylprop-2-en-1-ols

BF₃·OEt₂-catalyzed intermolecular reactions of arylmethylenecyclopropanes with (E)-1,1,3-triarylprop-2-en-1-ols produced the corresponding triene compounds, alcoholic derivatives or cyclobutane derivatives in moderate to excellent yields under mild conditions.     

Synthesis of thioamide-containing polystyrenes by Friedel–Crafts reaction and by thioamidation of (co)polydithioesters

Thioamide groups were introduced into polystyrenes by the Friedel–Crafts reaction, with phenyl isothiocyanate in nitromethane solution, in the presence of anhydrous aluminium chloride. Free radical copolymerization of 4-vinyl dithiobenzoate with styrene followed by low-temperature solution condensation reactions, with excess of amines in N,N-dimethylformamide, offered another synthetic route to (co)polymers containing thioamine groups in the side chains without crosslinking. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 117–127, 1998     

BF3·OEt2-catalyzed tandem Prins Friedel-Crafts reaction: a novel synthesis of sugar fused diarylhexahydro-2H-furo[3,2-b]pyrans

d-Glucose based homoallylic alcohol reacts smoothly with various aldehydes in the presence of arenes and a catalytic amount of BF₃·OEt₂ under mild conditions to afford a novel series of 5,7-diaryl-hexahydro-2H-furo[3,2-b]pyrans in good yields with high cis-selectivity.     

Highly efficient bimetallic iron‐palladium catalyzed Michael‐type Friedel–Crafts reactions of indoles with chalcones

Iron–palladium is a superior bimetallic catalyst in the presence of acetylacetone (Acac) with remarkable synergistic effect for the Michael‐type Friedel–Crafts reactions of indoles with chalcones. This catalytic system has the advantages of mild reaction conditions, smaller amount of metal salts, high yields of the desired products and operational simplicity, which make it a useful and promising process for the synthesis of indole derivatives. Copyright © 2009 John Wiley & Sons, Ltd.     

Iron‐Catalyzed Friedel–Crafts Benzylation with Benzyl TMS Ethers at Room Temperature

Friedel–Crafts benzylations between unactivated arenes and benzyl alcohol derivatives are clean and straightforward processes to construct biologically useful di‐ and tri‐arylmethanes. We have established an efficient iron‐catalyzed Friedel–Crafts benzylation method at room temperature that uses benzyl TMS ethers as substrates, which are poorly reactive under common nucleophilic substitution conditions. The reaction seems to progress through iron‐catalyzed self‐condensation of the benzyl TMS ether to the corresponding dibenzylic ether. The use of excess arene relative to benzyl TMS ether produced mono‐benzylated arene (di‐ and tri‐arylmethane products), whereas the use of excess benzyl TMS ether versus arene provided bis‐benzylated arene (polyarylated products) in high yields and regioselectivities. In previous methods, the latter double Friedel–Crafts benzylations hardly proceed.     

Organocatalytic Enantioselective Aza‐Friedel–Crafts Reaction of Cyclic Ketimines with Pyrroles using Imidazolinephosphoric Acid Catalysts

Organocatalytic enantioselective aza‐Friedel–Crafts reactions of cyclic ketimines with pyrroles or indoles were catalyzed by imidazoline/phosphoric acid catalysts. The reaction was applied to various 3H‐indol‐3‐ones to afford products in excellent yields and enantioselectivities. The chiral catalysts can be recovered by a single separation step using column chromatography and are reusable without further purification. Based on the experimental investigations, a possible transition state has been proposed to explain the origin of the asymmetric induction.     

Alkylation of acetals using manganate-BF3·OEt2 mixed reagent

A mixture of `R<sub>3</sub>MnMgBr' and BF<sub>3</sub>·OEt<sub>2</sub> prepared in advance only by stirring both reagents in ether converted acetals to alkylation products, where an alkoxy group of acetals was substituted by the alkyl group of manganese reagent used. Ketals also reacted with the `mixed reagent' to afford the corresponding alkylation products in high yield. α-Alkoxy-substituted cyclic ethers and acetoxy-substituted cyclic ethers were selectively converted to ring-opening alkylation products and α-alkyl-substituted cyclic ethers, respectively.     

Lewis acid catalyzed cascade reactions of diarylvinylidenecyclopropanes and 1,1,3-triarylprop-2-yn-1-ols or their methyl ethers

The reactions of vinylidenecyclopropanes 1 with 1,1,3-triarylprop-2-yn-1-ols or their methyl ethers 2 in the presence of a Lewis acid selectively produce 4-dihydro-1H-cyclopenta[b]naphthalene derivatives 3 or 1,2,3,8-tetrahydrocyclopenta[a]indene derivatives 4 depending on the substituents on the cyclopropane. Good to high yields are obtained under mild conditions. A plausible cascade Meyer-Schuster rearrangement and Friedel-Crafts reaction mechanism has been proposed. Moreover, novel functionalized methylenecyclobutene derivatives 5 could also be obtained in moderate to good yields under similar conditions when strongly electron-donating methoxy groups were introduced into the benzene rings of 2.     

NIS‐Assisted Aza‐Friedel–Crafts Reaction with α‐Carbamoysulfides as Precursors of N‐Carbamoylimines

A general and practical N‐iodosuccinimide (NIS)‐promoted aza‐Friedel–Crafts reaction of various aromatic nucleophiles with N‐acylimines generated in situ from α‐amidosulfides to give a rapid access to highly functionalized amines is described. The newly developed methodology is very mild, fast, efficient, and complementary.