Borane-Catalyzed Chemoselectivity-Controllable N-Alkylation and ortho C-Alkylation of Unprotected Arylamines Using Benzylic Alcohols

One-step synthesis of amphiphilic copolymers PDMS-b-PEG using tris(pentafluorophenyl)borane and subsequent study of encapsulation and release of curcumin

A series of amphiphilic block copolymer (BCP) micelles based on poly(dimethylsiloxane) (PDMS) and poly(ethylene glycol) (PEG) were synthesized by a one-step reaction in the presence of tris(pentafluorophenyl)borane (BCF) as a catalyst. The structural composition of PDMS-b-PEG (PR11) and PEG-b-PDMS-b-PEG (PR12) was corroborated by FTIR, 29Si NMR, and TGA. The BCPs were assembled in an aqueous solution, obtaining micelles between 57 and 87 nm in size. PR11 exhibited a higher (2.0 g L-1) critical micelle concentration (CMC) than PR12 (1.5 g L-1) due to the short chain length. The synthesized nano micelles were used to encapsulate curcumin, which is one of three compounds of turmeric plant 'Curcuma longa' with significant biological activities, including antioxidant, chemoprotective, antibacterial, anti-inflammatory, antiviral, and anti-depressant properties. The encapsulation efficiency of curcumin was 60% for PR11 and 45% for PR12. Regarding the release study, PR11 delivered 53% curcumin after five days under acidic conditions (pH of 1.2) compared to 43% at a pH of 7.4. The degradation products of curcumin were observed under basic conditions and were more stable at acidic pH. In both situations, the release process is carried out by breaking the silyl-ether bond, allowing the release of curcumin. PR11 showed prolonged release times, so it could be used to reduce ingestion times and simultaneously work as a nanocarrier for other hydrophobic drugs.

Impact of o-aryl halogen effects on ethylene polymerization: steric vs. electronic effects

Ligand steric hindrance and electronic effects play a crucial role in late-transition metal-catalyzed olefin polymerization. In this research, a series of o-aryl halogenated α-diimine ligands bearing bulky dibenzhydryl substituents, along with their corresponding nickel catalysts, have been synthesized and thoroughly characterized. The nickel catalysts demonstrated very high activity in ethylene polymerization, achieving a high rate of up to 107 g mol-1 h-1. The produced polyethylenes displayed a broad spectrum of molecular weights (12.2-871.7 kg mol-1) but maintained consistent branching densities (50-82/1000 C) when polymerized at a fixed temperature with different nickel catalysts. Notably, the polymerization temperature has a significant influence on both the molecular weight and branching density of the resulting polyethylene. Higher temperatures led to the formation of polyethylenes with lower molecular weights and increased branching densities. Interestingly, the o-aryl halogens significantly impact the molecular weight of the polyethylene. The size of the halogen substituents primarily determines the molecular weight of the polyethylene. However, in terms of branching density, the steric and electronic effects of these substituents appear to counteract each other. In addition, the branched high molecular weight polyethylenes from the bromine and chlorine substituted nickel catalysts are excellent polyethylene thermoplastic elastomers with high strain at break values (688-2478%) and high strain recovery values (42-62%).

Copper-Catalyzed Site-Selective Electrophilic Aromatic Alkylation of Monosubstituted Simple Arenes

A copper-catalyzed highly para-selective electrophilic aromatic alkylation of monosubstituted simple arenes has been accomplished. This method provides a practical platform for the transformation from simple commercial arenes to well-defined di- and multisubstituted aromatics with high added value. Control experiments and DFT calculations reveal that the achievement of the excellent site-selectivity is ascribed to the controlled deprotonation of the Wheland intermediates. Remarkably, the type of alkylating regent has been shown to have a significant impact on site-selectivity.

Desulfurative Functionalization of β-Acyl Allylic Sulfides with N-H Free Indoles Highly Regioselective at C3 and N1 Positions: Rapid Access to α-Branched Enones

A regiodivergent allylation of 1H-indoles highly selectively at the C3 and N1 positions with β-acyl allylic sulfides through desulfurative C-C/C-N bond-forming reactions has been developed under mild conditions. Notably, the remarkable site-selective switch can be achieved by a delicate choice of solvents and bases. This cost-efficient method displays a broad substrate scope, good functional compatibility, and excellent site-selectivity, thus offering a divergent synthesis of indole substituted α-branched enones, which possess diverse potential opportunities for further applications and derivatization.

Synthesis and Characterization of Slow-Release Chitosan Oligosaccharide Pyridine Schiff Base Copper Complexes with Antifungal Activity

Herein, a series of chitosan oligosaccharide copper complexes modified with pyridine groups (CPSx-Cu complexes) were successfully prepared via the Schiff base reaction and ion complexation reaction for slow-release fungicide. The structures of the synthesized derivatives were characterized via Fourier transform infrared spectroscopy and 1H and 13C nuclear magnetic resonance spectroscopy, and the unit configuration of the complexes was calculated using Gaussian software. The slow-release performance experiment demonstrated that the cumulative copper ion release rate of CPSx-Cu complexes was dependent on the type of substituents on the pyridine ring. Furthermore, the in vitro and in vivo antifungal activities of the CPSx-Cu complexes were investigated. At a concentration of 0.4 mg/mL, CPSx-Cu complexes completely inhibited the growth of Pythium vexans and Phytophthora capsici. Results indicated that CPSx-Cu complexes with slow-release ability exhibited better antifungal activity than thiodiazole-copper and copper sulfate basic. This study confirmed that combining chitosan oligosaccharide with bioactive pyridine groups and copper ions is an effective approach to further developing slow-release copper fungicides, providing new possibilities for the application of copper fungicides in green agriculture. This study lays the foundation for further studies on biogreen copper fungicides.

Direct Amination of α-Triaryl Alcohols via Vanadium Catalysis

α-Triaryl amines have been used as pharmaceuticals and pharmaceutical intermediates for antifungal and anticancer applications. Current methods to synthesize such compounds require at least two steps, and no direct amination of tertiary alcohols has been reported. Herein, we disclose efficient catalytic conditions for the direct amination of α-triaryl alcohols to access α-triaryl amines. VO(OⁱPr)₃, a commercially available reagent, has been identified as an effective catalyst for the direct amination of several α-triaryl alcohols. This process is scalable, as demonstrated by a gram-scale synthesis, and the reaction still works at as low as a 0.01 mol % catalyst loading with the turnover number reaching 3900. Moreover, commercial pharmaceuticals including clotrimazole and flutrimazole have been successfully prepared rapidly and efficiently using this newly developed method.

P(III)-Promoted Reductive Coupling of Aromatic and Aliphatic Nitro Compounds with Grignard Reagents

A phosphine-promoted reductive coupling of nitro compounds with Grignard reagents is described. Polyfunctional and pharmaceutically relevant diarylamines were generated by this reaction in moderate to high yields. Aliphatic nitro compounds that are highly challenging substrates undergo a combination of α-arylation and reductive coupling to afford the α-arylated arylamines efficiently. A series of valuable biaryl compounds with polyfluorinated and heteroaryl rings are co-generated in 56-94% yields.

Synergistic effect of hydrogen bonds and π-π interactions of B(C6F5)3·H2O/amides complex: Application in photoredox catalysis

B(C₆F₅)₃·H₂O has been long recognized as a common Brønsted acid. The lack of X-ray crystal structure of B(C₆F₅)₃·H₂O with other substrates has greatly limited the development of a new catalytic mode. In this work, a complex of B(C₆F₅)₃·H₂O and amide 2-phenyl-3,4-dihydroisoquinolin-1(2H)-one with hydrogen bonds and π-π interactions is characterized by X-ray diffraction. Such noncovalent interactions in solution also exist, as verified by NMR, UV-Vis absorption, and fluorescence emission measurements. Moreover, the mixture of amide 2-phenyl-3,4-dihydroisoquinolin-1(2H)-one and B(C₆F₅)₃·H₂O, instead of other tested Brønsted acids, shows a tailing absorption band in the visible light region (400-450 nm). Based on the photoactive properties of the complex, a photoredox catalysis is developed to construct α-aminoamides under mild conditions.

Ab Initio Metadynamics Simulations of Hexafluoroisopropanol Solvent Effects: Synergistic Role of Solvent H-Bonding Networks and Solvent-Solute C-H/π Interactions

The solvent effects in Friedel-Crafts cycloalkylation of epoxides and Cope rearrangement of aldimines were investigated by using ab initio molecular dynamics simulations. Explicit molecular treatments were applied for both reactants and solvents. The reaction mechanisms were elucidated via free energy calculations based on metadynamics simulations. The results reveal that both reactions proceed in a concerted fashion. Key solvent-substrate interactions are identified from the structures of transition states with explicit solvent molecules. The remarkable promotion effect of hexafluoroisopropanol solvent is ascribed to the synergistic effect of H-bonding networks and C-H/π interactions with substrates.

Oxidative cross-coupling of quinoxalinones with indoles enabled by acidochromism

An oxidative cross-coupling of quinoxalinones with indole derivatives via B(C₆F₅)₃·H₂O induced acidochromism of quinoxalinone derivatives was developed under mild and external photocatalyst-free conditions. The reaction shows excellent substrate scope, accommodating a wide range of functional groups. The usefulness of this strategy was demonstrated by the synthesis of the natural products Azacephalandole A and Cephalandole A in high yields. Moreover, the products are fluorophores showing prevalent fluorescence properties with a wide emission range and good relative quantum yields.

Boron Lewis Acid Catalysis Enables the Direct Cyanation of Benzyl Alcohols by Means of Isonitrile as Cyanide Source

The development of an efficient and straightforward method for cyanation of alcohols is of great value. However, the cyanation of alcohols always requires toxic cyanide sources. Herein, an unprecedented synthetic application of an isonitrile as a safer cyanide source in B(C₆F₅)₃-catalyzed direct cyanation of alcohols is reported. With this approach, a wide range of valuable α-aryl nitriles was synthesized in good to excellent yields (up to 98%). The reaction can be scaled up and the practicability of this approach is further manifested in the synthesis of an anti-inflammatory drug, naproxen. Moreover, experimental studies were performed to illustrate the reaction mechanism.

N, S Co-Coordinated Zinc Single-Atom Catalysts for N-Alkylation of Aromatic Amines with Alcohols: The Role of S-Doping in the Reaction

S-doping emerged as a promising approach to further improve the catalytic performance of carbon-based materials for organic synthesis. Herein, a facile and gram-scale strategy was developed using zeolitic imidazole frameworks (ZIFs) as a precursor for the fabrication of the ZIF-derived N, S co-doped carbon-supported zinc single-atom catalyst (CNS@Zn₁-AA) via the pyrolysis of S-doped ZIF-8, which was modified by aniline, ammonia and thiourea and prepared by one-pot ball milling at room temperature. This catalyst, in which Zn is dispersed as the single atom, displays superior activity in N-alkylation via the hydrogen-borrowing strategy (120 °C, turnover frequency (TOF) up to 8.4 h^-1). S-doping significantly enhanced the catalytic activity of CNS@Zn₁-AA, as it increased the specific surface area and defects of this material and simultaneously increased the electron density of Zn sites in this catalyst. Furthermore, this catalyst had excellent stability and recyclability, and no obvious loss in activity after eight runs.

Stereoselective Construction of Tertiary Homoallyl Alcohols and Ethers by Nucleophilic Substitution at Quaternary Carbon Stereocenters

An efficient method for the stereoselective construction of tertiary C-O bonds via a stereoinvertive nucleophilic substitution at the quaternary carbon stereocenter of cyclopropyl carbinol derivatives using water, alcohols and phenols as nucleophiles has been developed. This substitution reaction proceeds under mild conditions and tolerates several functional groups, providing a new access to the stereoselective formation of highly congested tertiary homoallyl alcohols and ethers.

Dehydrative amination of benzhydrols with electron-withdrawing group-substituted 2-aminopyridines utilizing Au(III)/TPPMS catalyst system in water

We report a method for gold(III)/sodium diphenylphosphinobenzene-3-sulfonate (TPPMS)-catalyzed direct amination of benzhydrols using 2-aminopyridines with poor nucleophilic character in water. Various functional groups such as electron-withdrawing nitro, cyano and halogen groups were tolerated well to form the desired N-benzylated 2-aminopyridine compounds. On the basis of mechanistic studies including kinetic profiles, Hammett study and isotope effects, we propose a pathway in which a Lewis acidic gold cation species activates the sp³ C-O bond of the alcohol in the rate-determining step.

Solvent-controlled regioselective C(5)-H/N(1)-H bond alkylations of indolines and C(6)-H bond alkylations of 1,2,3,4-tetrahydroquinolines with para-quinone methides

Solvent-promoted and -controlled regioselective bond alkylation reactions of para-quinone methides (p-QMs) with N-H free-indoline and 1,2,3,4-tetrahydroquinoline (THQ) under metal-free conditions have been developed. In the presence of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as the solvent, 1,6-addition alkylation reactions of p-QMs with NH-free indolines and THQs efficiently gave C5-alkylated indolines and C6-alkylated THQs. Using catalytic amounts of HFIP in DCM, the reaction of indolines and p-QMs resulted in the alkylation of indolines at the N1-position. HFIP plays two roles in the reactions: converting the indoline and THQ into bidentate nucleophiles and activating the p-QMs to achieve the 1,6-addition alkylation via hydrogen bond clusters. The indoline and THQ act as a C-nucleophile due to the H-bond clusters between HFIP and the nitrogen atom, whereas upon using catalytic amounts of HFIP, the compounds act as an N-nucleophile. All alkylation products were transformed into the corresponding indoles and quinolines via oxidation in the presence of diethyl azodicarboxylate (DEAD). Furthermore, the synthetic utilities have been showcased with both the removal of the tert-butyl groups from the C5-alkylated indole products and submission to their Suzuki coupling reactions.

Friedel-Crafts Benzylation of Unprotected Anilines with Indole-3- carbinols to Access Trifluoro-methyl(indolyl)phenylmethanes

:

An unprecedented protocol for the efficient and highly chemoselective alkylation of unprotected anilines with deactivated CF3-indole-3-carbinols promoted by In(OTf)3 has been developed. A series of diversified trifluoromethylated (indolyl)phenylmethanes were produced featuring the C-alkylation in moderate to high chemical yields and with high regioselectivities.

Boron Lewis Acid Catalyzed Intermolecular trans-Hydroarylation of Ynamides with Hydroxyarenes

An atom-economic protocol for the efficient and highly chemo- and stereoselective trans-hydroarylation of ynamides with hydroxyarenes catalyzed by B(C₆F₅)₃ has been developed. Use of readily available starting materials, low catalyst loading, mild reaction conditions, a broad substrate scope, ease of scale-up, and versatile functionalizations of the enamide products make this approach very practical and attractive.

Arylboronic Acid Catalyzed Dehydrative Mono-/Dialkylation Reactions of β-Ketoacids and Alcohols

The dehydrative mono-/dialkylation reactions of alcohols and β-ketoacids were realized under arylboronic acid catalysis, furnishing a series of β-aryl ketones and β-ketoesters in yields of 15-99%, with CO₂ and H₂O being the byproducts. In this context, the decarboxylative alkylation reaction occurred to give β-aryl ketones at 50 °C, while the decarboxylation was suppressed to generate dialkylated ester products at 0 °C. A possible catalytic cycle was proposed based on control experiments.

A Theoretical Study on the Borane-Catalyzed Reductive Amination of Aniline and Benzaldehyde with Dihydrogen: The Origins of Chemoselectivity

Density functional theory calculations are used in this study to investigate the product selectivity and mechanism of borane-catalyzed reductive aldehyde amination by a H₂ reducing agent. Knowing that different boranes yield different products, two typical boranes, (B(2,6-Cl₂C₆H₃)(p-HC₆F₄)₂ and B(C₆F₅)₃), are studied. Of the seven possible pathways of B(2,6-Cl₂C₆H₃)(p-HC₆F₄)₂-catalyzed aldehyde amination analyzed herein, four are favorable. Three of the four favorable pathways involve imine intermediates, and the fourth is a Lewis acid-base synergistic pathway that involves amine-alcohol condensation. As for the B(C₆F₅)₃ catalyst, it forms a highly stable Lewis adduct with aniline, which impedes the hydrogenation of imine. Therefore, the product of B(C₆F₅)₃-catalyzed reductive amination of benzaldehyde and aniline is an imine. The linear relationship between the charge on the boron atom in the Lewis acid and the relative energies of the Lewis adduct and H₂ splitting transition state indicates that this parameter determines product selectivity. Indeed, when the natural charge on boron is larger than 1, an amine is produced, whereas when the charge is less than 1, an imine is produced. Hence, the selectivity of products can be controlled by adjusting the natural charge of the boron atom in the Lewis acid catalyst.

Direct activation of alcohols via perrhenate ester formation for an intramolecular dehydrative Friedel–Crafts reaction

A general and highly efficient intramolecular dehydrative Friedel–Crafts reactions via Re2O7 mediated hydroxyl group activation is described for the syntheses of tetrahydronaphthalene, tetrahydroquinoline, tetrahydroisoquinoline, chromane, and isochromane derivatives.

Boron-Based Lewis Acid Catalysis: Challenges and Perspectives

In the last two decades, boron-based catalysis has been gaining increasing traction in the field of organic synthesis. The use of halogenated triarylboranes as main group Lewis acid catalysts is an attractive strategy. It has been applied in a growing number of transformations over the years, where they may perform comparably or even better than the gold standard catalysts. This review discusses methods of borane synthesis and cutting-edge boron-based Lewis acid catalysis, focusing especially on tris(pentafluorophenyl)-borane [B(C6F5)3], and other halogenated triarylboranes, highlighting how boron Lewis acids employed as catalysts can unlock a plethora of unprecedented chemical transformations or improve the efficiency of existing reactions.

Borane-Catalyzed Carbazolation Reactions of Aryldiazoacetates

Herein, we report on the tris(pentafluorophenyl)borane-catalyzed reaction of carbazole heterocycles with aryldiazoacetates. We could demonstrate that selective N-H functionalization occurs in the case of an unprotected carbazole, other N-heterocycles, and secondary amines in good yields. In contract, the protected carbazole undergoes C-H functionalization at the C-3 position in a good yield. The application of both approaches was studied in 41 examples with up to a 97% yield.

B(C6F5)3-Catalyzed Sequential Additions of Terminal Alkynes to para-Substituted Phenols: Selective Construction of Congested Phenol-Substituted Quaternary Carbons

We have developed a borane-catalyzed sequential addition of terminal alkynes to para-substituted phenols, which affords a wide range of ortho-propargylic alkylated phenols bearing congested quaternary carbons. Control experiments combined with DFT calculations suggest that the reaction undergoes a sequential phenol alkenylation/hydroalkynylation process. Further extension of this strategy to the construction of triaryl-substituted quaternary carbons demonstrates the broad utility of this method.

Mimicking transition metals in borrowing hydrogen from alcohols

Borrowing hydrogen from alcohols, storing it on a catalyst and subsequent transfer of the hydrogen from the catalyst to an in situ generated imine is the hallmark of a transition metal mediated catalytic N-alkylation of amines. However, such a borrowing hydrogen mechanism with a transition metal free catalytic system which stores hydrogen molecules in the catalyst backbone is yet to be established. Herein, we demonstrate that a phenalenyl ligand can imitate the role of transition metals in storing and transferring hydrogen molecules leading to borrowing hydrogen mediated alkylation of anilines by alcohols including a wide range of substrate scope. A close inspection of the mechanistic pathway by characterizing several intermediates through various spectroscopic techniques, deuterium labelling experiments, and DFT study concluded that the phenalenyl radical based backbone sequentially adds H+, H˙ and an electron through a dearomatization process which are subsequently used as reducing equivalents to the C-N double bond in a catalytic fashion.

Tris(pentafluorophenyl)borane catalyzed C-C and C-heteroatom bond formation

A series of boron based Lewis acids have been reported to date, but among them, tris(pentafluorophenyl)borane (BCF) has gained the most significant attention in the synthetic chemistry community. The viability of BCF as a potential Lewis acid catalyst has been vastly explored in organic and materials chemistry due to its thermal stability and commercial availability. Most explorations of BCF chemistry in organic synthesis has occurred in the last two decades and many new catalytic reactivities are currently under investigation. This review mainly focuses on recent reports from 2018 onwards and provides a concise knowledge to the readers about the role of BCF in metal-free catalysis. The review has mainly been categorized by different types of organic transformation mediated through BCF catalysis for the C-C and C-heteroatom bond formation.

Electron-deficient boron-based catalysts for C-H bond functionalisation

In contrast to transition metal-catalysed C-H functionalisation, highly efficient construction of C-C and C-X (X = N, O, S, B, Si, etc.) bonds through metal-free catalytic C-H functionalisation remains one of the most challenging tasks for synthetic chemists. In recent years, electron-deficient boron-based catalyst systems have exhibited great potential for C-H bond transformations. Such emerging systems may greatly enrich the chemistry of C-H functionalisation and main-group element catalysis, and will also provide enormous opportunities in synthetic chemistry, materials chemistry, and chemical biology. This article aims to give a timely comprehensive overview to recognise the current status of electron-deficient boron-based catalysis in C-H functionalisation and stimulate the development of more efficient catalytic systems.

Brønsted Acid-Catalysed Dehydrative Substitution Reactions of Alcohols

The direct, catalytic dehydrative substitution of alcohols is a challenging, yet highly desirable process in the development of more sustainable approaches to organic chemistry. This review outlines recent advances in Brønsted acid-catalysed dehydrative substitution reactions for C-C, C-O, C-N and C-S bond formation. The wide range of processes that are now accessible using simple alcohols as the formal electrophile are highlighted, while current limitations and therefore possible future directions for research are also discussed.

Catalyst-free synthesis of α,α-disubstituted carboxylic acid derivatives under ambient conditions via a Wolff rearrangement reaction

Herein, a hexafluoroisopropanol (HFIP)-promoted Wolff rearrangement reaction was developed, delivering various α,α-disubstituted carboxylic acid derivatives in good to excellent yields.

Synthesis of Titanium Complexes Supported by Carbinolamide- and Amide-Containing Ligands Derived from Ti(NMe2)4-Mediated Selective Amidations of Carbonyl Groups

An efficient strategy for the syntheses of a series of titanium complexes has been developed. This protocol features the employment of Ti(NMe₂)₄ both as the metal center to trigger the deprotonation of the ligands and as an amine source to proceed the amidation reactions of carbonyl functionalities of the ligands. Treatment of Ti(NMe₂)₄ with a ligand HL1 (HL1 = 2,2'-(((2-hydroxybenzyl)azanediyl)bis(ethane-2,1-diyl))bis(isoindoline-1,3-dione) results in the formation of Ti(L1')(NMe₂) (1) (H₃L1' = N1-(2-((2-(1-(dimethylamino)-1-hydroxy-3-oxoisoindolin-2-yl)ethyl)(2-hydroxybenzyl)amino)ethyl)-N2,N2-dimethylphthalamide). One important feature regarding the synthesis of 1 is the occurrence of the in situ metal-ligand reaction between Ti(NMe₂)₄ and HL1, leading to the simultaneous formations of carbinolamide and amide scaffolds. Another prominent feature in terms of the preparation of 1 is the achievement of the selective ring-opening reaction of one of the two phthalimide units of the HL1 ligand, affording carbinolamide and amide functionalities within one ligand set. The developed methodology characterizes an ample substrate scope. The selective amidation reactions of the carbonyl groups have been realized for a series of analogous ligands HL2-HL7. Density functional theory calculations were employed to disclose the mechanisms for the formation of 1-7, and the details for the selective ring-opening reactions of the phthalimide unit were uncovered.

B(C6 F5 )3 -Catalyzed Tandem Friedel-Crafts and C-H/C-O Coupling Reactions of Dialkylanilines

Tandem Friedel-Crafts (FC) and C-H/C-O coupling reactions catalyzed by tris(pentafluorophenyl) borane (B(C₆ F₅ )₃ ) were achieved without using any other additive in the absence of solvent. This process can be used for the reactions between a series of dialkylanilines and vinyl ethers with good isolated yields of bis(4-dialkylaminophenyl) compounds. Based on combined theoretical and experimental studies, the possible reaction mechanism was proposed. B(C₆ F₅ )₃ can activate the C=C and C-O bond for FC and C-H/C-O coupling reactions respectively. The FC reaction is slow, which is followed by a fast C-H/C-O coupling.

Exploiting hexafluoroisopropanol (HFIP) in Lewis and Brønsted acid-catalyzed reactions

Hexafluoroisopropanol (HFIP) is a solvent with unique properties that has recently gained attention for promoting a wide range of challenging chemical reactions. It was initially believed that HFIP was almost exclusively involved in the stabilization of cationic intermediates, owing to its high polarity and low nucleophilicity. However, in many cases, the mechanism of action of HFIP appears to be more complex. Recent findings reveal that many Lewis and Brønsted acid-catalyzed transformations conducted in HFIP additionally involve cooperation between the catalyst and HFIP hydrogen-bond clusters, akin to Lewis- or Brønsted acid-assisted-Brønsted acid catalysis. This feature article showcases the remarkable versatility of HFIP in Lewis and Brønsted acid-catalyzed reactions, with an emphasis on examples yielding mechanistic insight.

Triarylborane catalysed N-alkylation of amines with aryl esters

B(C₆F₅)₃ is demonstrated to be an active catalyst for N-alkylation reactions of amine substrates with aryl esters.

Boron-Catalyzed N-Alkylation of Arylamines and Arylamides with Benzylic Alcohols

A sustainable boron-based catalytic approach for chemoselective N-alkylation of primary and secondary aromatic amines and amides with primary, secondary, and tertiary benzylic alcohols has been presented. The metal-free protocol operates at low catalyst loading, tolerates several functional groups, and generates H₂O as the sole byproduct. Preliminary mechanistic studies were performed to demonstrate the crucial role of boron catalyst for the activation of the intermediate dibenzyl ether and to identify the rate-determining step.