Copper-Catalyzed Hydroxylation of (Hetero)aryl Halides under Mild Conditions

Protocol for hydroxylating aryl chlorides catalyzed by photouranium with water under ambient conditions

Here, we present a protocol for the hydroxylation of aryl chlorides catalyzed by photouranium with water under ambient conditions. We describe steps for gram-scale hydroxylation of 2'-chloroacetophenone using our self-designed continuous-flow photoreactor. We then detail procedures for obtaining 2'-hydroxyacetophenone using our self-designed rapid separation and purification instrument. This protocol is not suitable for polycyclic and heterocyclic aryl chlorides. For complete details on the use and execution of this protocol, please refer to Sun et al.1.

6-Hydroxy Picolinohydrazides Promoted Cu(I)-Catalyzed Hydroxylation Reaction in Water: Machine-Learning Accelerated Ligands Design and Reaction Optimization

Hydroxylated (hetero)arenes are privileged motifs in natural products, materials, small-molecule pharmaceuticals and serve as versatile intermediates in synthetic organic chemistry. Herein, we report an efficient Cu(I)/6-hydroxy picolinohydrazide-catalyzed hydroxylation reaction of (hetero)aryl halides (Br, Cl) in water. By establishing machine learning (ML) models, the design of ligands and optimization of reaction conditions were effectively accelerated. The N-(1,3-dimethyl-9H- carbazol-9-yl)-6-hydroxypicolinamide (L32, 6-HPA-DMCA) demonstrated high efficiency for (hetero)aryl bromides, promoting hydroxylation reactions with a minimal catalyst loading of 0.01 mol % (100 ppm) at 80 °C to reach 10000 TON; for substrates containing sensitive functional groups, the catalyst loading needs to be increased to 3.0 mol % under near-room temperature conditions. N-(2,7-Di-tert-butyl-9H-carbazol-9-yl)-6-hydroxypicolinamide (L42, 6-HPA-DTBCA) displayed superior reaction activity for chloride substrates, enabling hydroxylation reactions at 100 °C with 2-3 mol % catalyst loading. These represent the state of art for both lowest catalyst loading and temperature in the copper-catalyzed hydroxylation reactions. Furthermore, this method features a sustainable and environmentally friendly solvent system, accommodates a wide range of substrates, and shows potential for developing robust and scalable synthesis processes for key pharmaceutical intermediates.

Oxalamide ligands with additional coordinating groups for Cu-catalyzed arylation of alcohols and phenols

A novel class of chain-like multidentate oxalamide ligands with additional coordinating groups was developed for the coupling of (hetero)aryl bromides with both alcohols and phenols under mild conditions. Introduction of oxygen atoms in N-alkyl chains is pivotal for the high catalytic efficiency and broad substrate versatility.

Non-benzenoid N-aryl oxalamide: synthesis of troponyl-oxalamide peptides by Pd(II)-catalyzed C(sp3)-H functionalization of glycinamides

Aryl oxalamides are constituents of various promising drug-like molecules. Their aryl groups are derived from the benzenoid aromatic moiety. However, non-benzenoid aromatic molecules, troponoids, are found in various bioactive natural products. It would be thought-provoking to explore non-benzenoid aryl oxalamide derivatives. This report describes the synthesis of N-troponyl-oxalamide peptides by Pd(II)-catalyzed C(sp3)-H functionalization of N-troponyl glycinate peptides. This is the first instance of β-hydride elimination at the palladium complex of N-troponyl glycinates that generates imine in situ, rendering the synthesis of oxalamides. Importantly, the crystal structures of representative oxalamide derivatives form distinctive foldameric structures, such as β-sheet type structures, owing to the presence of additional troponyl carbonyl groups. Hence, these non-benzenoid oxalamides are potential scaffolds for tuning the structure and function of N-troponyl peptides, which could provide innovative avenues of research in the development of emerging structural and functional peptides.

Product Selectivity in Baeyer-Villiger Monooxygenase-Catalyzed Bacterial Alkaloid Core Structure Maturation

Baeyer-Villiger monooxygenases (BVMOs) play crucial roles in the core-structure modification of natural products. They catalyze lactone formation by selective oxygen insertion into a carbon-carbon bond adjacent to a carbonyl group (Baeyer-Villiger oxidation, BVO). The homologous bacterial BVMOs, BraC and PxaB, thereby process bicyclic dihydroindolizinone substrates originating from a bimodular nonribosomal peptide synthetase (BraB or PxaA). While both enzymes initially catalyze the formation of oxazepine-dione intermediates following the identical mechanism, the final natural product spectrum diverges. For the pathway involving BraC, the exclusive formation of lipocyclocarbamates, the brabantamides, was reported. The pathway utilizing PxaB solely produces pyrrolizidine alkaloids, the pyrrolizixenamides. Surprisingly, replacing pxaB within the pyrrolizixenamide biosynthetic pathway by braC does not change the product spectrum to brabantamides. Factors controlling this product selectivity have remained elusive. In this study, we set out to solve this puzzle by combining the total synthesis of crucial pathway intermediates and anticipated products with in-depth functional in vitro studies on both recombinant BVMOs. This work shows that the joint oxazepine-dione intermediate initially formed by both BVMOs leads to pyrrolizixenamides upon nonenzymatic hydrolysis, decarboxylative ring contraction, and dehydration. Brabantamide biosynthesis is enzyme-controlled, with BraC efficiently transforming all the accepted substrates into its cognate final product scaffold. PxaB, in contrast, shows only considerable activity toward brabantamide formation for the substrate analog with a natural brabantamide-type side chain structure, revealing substrate-controlled product selectivity.

CuI/Oxalamide-Catalyzed Coupling Reaction of (Hetero)aryl Halides with Sodium Nitrite

The N,N'-bis(thiophen-2-ylmethyl)oxalamide (BTMO) was found to be an effective ligand for Cu-catalyzed ipso-nitration of (hetero)aryl halides (Br, I), making the coupling reaction with sodium nitrite proceed smoothly at 100-120 °C with 1-5 mol % CuI and BTMO. Electron-rich substrates were the best coupling partners to give the desired coupling products in good to excellent yields at 100 °C. Electron-neutral substrates required heating at 120 °C to get complete conversion, while rather low conversions were observed in the case of electron-poor (hetero)aryl bromides.

Direct C-H Hydroxylation of N-Heteroarenes and Benzenes via Base-Catalyzed Halogen Transfer

Hydroxylated (hetero)arenes are valued in many industries as both key constituents of end products and diversifiable synthetic building blocks. Accordingly, the development of reactions that complement and address the limitations of existing methods for the introduction of aromatic hydroxyl groups is an important goal. To this end, we apply base-catalyzed halogen transfer (X-transfer) to enable the direct C-H hydroxylation of mildly acidic N-heteroarenes and benzenes. This protocol employs an alkoxide base to catalyze X-transfer from sacrificial 2-halothiophene oxidants to aryl substrates, forming SNAr-active intermediates that undergo nucleophilic hydroxylation. Key to this process is the use of 2-phenylethanol as an inexpensive hydroxide surrogate that, after aromatic substitution and rapid elimination, provides the hydroxylated arene and styrene byproduct. Use of simple 2-halothiophenes allows for C-H hydroxylation of 6-membered N-heteroarenes and 1,3-azole derivatives, while a rationally designed 2-halobenzothiophene oxidant extends the scope to electron-deficient benzene substrates. Mechanistic studies indicate that aromatic X-transfer is reversible, suggesting that the deprotonation, halogenation, and substitution steps operate in synergy, manifesting in unique selectivity trends that are not necessarily dependent on the most acidic aryl position. The utility of this method is further demonstrated through streamlined target molecule syntheses, examples of regioselectivity that contrast alternative C-H hydroxylation methods, and the scalable recycling of the thiophene oxidants.

Synthesis of meta-carbonyl phenols and anilines

Phenols and anilines are of extreme importance for medicinal chemistry and material science. The development of efficient approaches to prepare both compounds has thus long been a vital research topic. The utility of phenols and anilines directly reflects the identity and pattern of substituents on the benzenoid ring. Electrophilic substitutions remain among the most powerful synthetic methods to substituted phenols and anilines, yet in principle achieving ortho- and para-substituted products. Therefore, the selective preparation of meta-substituted phenols and anilines is the most significant challenge. We herein report an efficient copper-catalyzed dehydrogenation strategy to exclusively synthesize meta-carbonyl phenols and anilines from carbonyl substituted cyclohexanes. Mechanistic studies indicate that this transformation undergoes a copper-catalyzed dehydrogenation/allylic hydroxylation or amination/oxidative dehydrogenation/aromatization cascade process.

Base-promoted triple cleavage of CCl2Br: a direct one-pot synthesis of unsymmetrical oxalamide derivatives

We present a novel, eco-friendly and one-pot approach for synthesizing unsymmetrical oxalamides with the aid of dichloroacetamide and amine/amides in the presence of CBr4 in a basic medium. The use of water as a potent supplement for the oxygen atom source and the detailed mechanism have been disclosed. Moreover, the protocol involves triple cleavage of CCl2Br and the formation of new C-O/C-N bonds, with the advantage of achieving selective bromination using CBr4 with good to excellent yield under mild conditions. The method also demonstrates promise for industrial use, as proven by its effective implementation in gram-scale synthesis conducted in a batch process, along with its utilization in a continuous-flow system.

Late-stage modification of bioactive compounds: Improving druggability through efficient molecular editing

Synthetic chemistry plays an indispensable role in drug discovery, contributing to hit compounds identification, lead compounds optimization, candidate drugs preparation, and so on. As Nobel Prize laureate James Black emphasized, "the most fruitful basis for the discovery of a new drug is to start with an old drug"1. Late-stage modification or functionalization of drugs, natural products and bioactive compounds have garnered significant interest due to its ability to introduce diverse elements into bioactive compounds promptly. Such modifications alter the chemical space and physiochemical properties of these compounds, ultimately influencing their potency and druggability. To enrich a toolbox of chemical modification methods for drug discovery, this review focuses on the incorporation of halogen, oxygen, and nitrogen-the ubiquitous elements in pharmacophore components of the marketed drugs-through late-stage modification in recent two decades, and discusses the state and challenges faced in these fields. We also emphasize that increasing cooperation between chemists and pharmacists may be conducive to the rapid discovery of new activities of the functionalized molecules. Ultimately, we hope this review would serve as a valuable resource, facilitating the application of late-stage modification in the construction of novel molecules and inspiring innovative concepts for designing and building new drugs.

Hydroxylation of Aryl Sulfonium Salts for Phenol Synthesis under Mild Reaction Conditions

Hydroxylation of aryl sulfonium salts could be realized by utilizing acetohydroxamic acid and oxime as hydroxylative agents in the presence of cesium carbonate as a base, leading to a variety of structurally diverse hydroxylated arenes in 47-95% yields. In addition, the reaction exhibited broad functionality tolerance, and a range of important functional groups (e.g., cyano, nitro, sulfonyl, formyl, keto, and ester) could be well amenable to the mild reaction conditions.

Copper-Catalyzed α-Arylation of Nitroalkanes with (Hetero)aryl Bromides/Iodides

α-Aryl substituted nitroalkanes are valuable synthetic building blocks that can be easily converted into α-aryl substituted aldehydes, ketones, carboxylic acids, as well as amines. Herein, an efficient Cu/oxalamide-catalyzed coupling between nitroalkanes and (hetero)aryl halides (Br, I) was developed to direct access highly diverse α-aryl substituted nitroalkanes. Compared with the current state of art, this protocol is more environmentally friendly and practical for synthetic chemists. This approach is characterized by a broad substrate scope on both nitroalkane part (primary nitroalkanes and nitromethane) and sp2 halide part ((hetero)aryl bromides/iodides and alkenyl bromides/iodides). The excellent functional group tolerance was observed, which would enable real world synthetic applications. More importantly, TON of current transformation reached to 3640, when some aryl iodides were used as coupling partners. This represents currently the highest catalyst turnover for transition-metal catalyzed α-arylation of nitroalkanes. Furthermore, the successful application in late-stage modification of complex molecules and synthesis of a known retinoid X receptor (RXR) antagonist exemplified its synthetic potential.

A General Copper Catalytic System for Suzuki-Miyaura Cross-Coupling of Unactivated Secondary and Primary Alkyl Halides with Arylborons

Suzuki-Miyaura cross-couplings (SMC) are powerful tools for the construction of carbon-carbon bonds. However, the couplings of sp3-hybridized alkyl halides with arylborons often encounter several problematic issues such as sluggish oxidation addition of alkyl halides and competitive β-hydride elimination side pathways of metal-alkyl species. In precedent reports, copper is mainly utilized for the coupling of sp2-aryl halides, and the cross-couplings with unactivated alkyl halides are far less reported. Herein, we demonstrate that a high-efficiency copper system enabled the coupling of arylborons with various unactivated secondary and primary alkyl halides including bromides, iodides, and even robust chlorides. The present system features broad scope, excellent functionality tolerance, scalability, and practicality. Moreover, the current system could be applied for the late-stage functionalization of complex molecules in moderate to high efficiency.

Copper-Catalyzed Asymmetric Arylation of α-Substituted Cyanoacetates Enabled by Chiral Amide Ligands

The (S)-nobin-embodied picolinamide and L-hydroxyproline-derived amide are effective ligands for Cu-catalyzed enantioselective coupling reaction of (hetero)aryl iodides with α-alkyl substituted cyanoacetates. This arylation reaction gave α-(heteroaryl)-α-alkyl cyanoacetates in good to excellent enantioselectivities (up to 95 % ee). A variety of functionalized (hetero)aryl and alkyl groups could be introduced to the quaternary center and therefore provided a valuable tool for preparing enantioenriched compounds with an all-carbon quaternary center tethered with convertible functional groups. The size of both α-alkyl and ester groups was proven as the key factor for asymmetric induction.

A novel tetranuclear Cu(ii) complex for DNA-binding and in vitro anticancer activity

A novel tetranuclear Cu(ii) complex (TNC) was successfully synthesized and characterized by X-ray single crystal diffraction. The interaction of the complex with calf thymus DNA (CT-DNA) has been studied by UV-vis absorption titration, fluorescence technology and molecular docking. The results indicated that TNC could bind to the DNA through an intercalative mode. The agarose gel electrophoresis experiment showed that TNC could cleave supercoiled plasmid DNA into linear DNA. The anticancer activity of TNC was tested on four cancer cell lines: MCF7, A549, 4T1 and HepG2. The results indicated that TNC shown significant activity against all of above cell lines.

[2+2+1+1] Cycloaddition for de novo Synthesis of Densely Functionalized Phenols

A unique benzannulation strategy for regioselective de novo synthesis of densely functionalized phenols is described. Through metal-mediated formal [2+2+1+1] cycloaddition of two different alkynes and two molecules of CO, a series of densely functionalized phenols were obtained. The benzannulation strategy allows efficient regioselective installation up to five different substituents on a phenol ring. The resulting phenols have a substitution pattern different from those obtained from Dötz and Danheiser benzannulations.

Denitrative Hydroxylation of Unactivated Nitroarenes

A one-step method for the conversion of nitroarenes into phenols under operationally simple, transition-metal-free conditions is described. This denitrative functionalization protocol provides a concise and economical alternative to conventional three-step synthetic sequences. Experimental and computational studies suggest that nitroarenes may be substituted by an electron-catalysed radical-nucleophilic substitution (S_RN 1) chain mechanism.

Chemoenzymatic Synthesis of (+)-Xyloketal B

Xyloketal B is a pentacyclic fungal marine natural product that has shown potential for the treatment of diseases such as Alzheimer's disease and atherosclerosis. Herein, we describe the first asymmetric synthesis of this natural product, which relies on a chemoenzymatic strategy. This approach leverages a biocatalytic benzylic hydroxylation to access to an ortho-quinone methide intermediate which is captured in a [4 + 2] cycloaddition to stereoselectively yield a key cyclic ketal intermediate enroute to (+)-xyloketal B. The relative configuration of this intermediate was rapidly confirmed as the desired stereoisomer using MicroED. To complete the synthesis, a second ortho-quinone methide was accessed through a reductive approach, ultimately leading to the stereoselective synthesis of (+)-xyloketal B.

Cu/Oxalic Diamide-Catalyzed Coupling of Terminal Alkynes with Aryl Halides

N¹-(2,6-Dimethylphenyl)-N²-(pyridin-2-ylmethyl)oxalamide (DMPPO) was revealed to be a more effective ligand for copper-catalyzed coupling reaction of (hetero)aryl halides with 1-alkynes than previously reported ones. Only 3 mol % CuCl and DMPPO are required to make the coupling complete at 100 °C (for bromides) and 80 °C (for iodides). Both (hetero)aryl and alkyl substituted 1-alkynes worked well under these conditions, leading to the formation of internal alkynes in great diversity.

PhI(OAc)2/Pd(OAc)2 promoted the formation of 8-hydroxyquinoline derivatives from benzoxazoles and alcohols

A PhI(OAc)₂/Pd(OAc)₂ system that synergistically promotes the formation of 8-hydroxyquinoline derivatives from benzoxazoles and alcohols has been developed. The reaction proceeded smoothly with a range of benzoxazoles and alcohols to give the corresponding 8-hydroxyquinoline derivatives in moderate yields.

Structure-Activity Relationships of Styrylquinoline and Styrylquinoxaline Derivatives as α-Synuclein Imaging Probes

Synucleinopathies are characterized by the deposition of α-synuclein (α-syn) aggregates before the onset of clinical symptoms. Therefore, in vivo imaging of α-syn may contribute to early diagnosis of these diseases and has attracted much attention in recent years. However, no clinically useful probes have been reported. In the present study, 16 quinoline/quinoxaline derivatives with different styryl and fluorine groups were evaluated in order to develop α-syn imaging probes. Among them, SQ3, which is a quinoline analogue with a p-(dimethylamino)styryl group and fluoroethoxy group at the 2- and 7- positions of the skeleton, displayed moderate selectivity for α-syn aggregates over β-amyloid (Aβ) aggregates (K i = 230 nM), while maintaining high binding affinity for α-syn aggregates (K i = 39.3 nM). In a biodistribution study, [18F]SQ3 exhibited high uptake (2.08% ID/g at 2 min after intravenous injection) into a normal mouse brain. Taken together, we demonstrate that [18F]SQ3 has basic properties as a lead compound for the development of a useful α-syn imaging probe.

Total Synthesis of the Phenolic Steroid Myrmenaphthol A

Myrmenaphthol A is a structurally unique phenolic steroid with a naphthyl AB-ring system and an unusual C2 hydroxy group. Herein, we report the first total synthesis of this natural product in 10 steps from inexpensive, commercially available sitolactone. Key features of the synthesis include a Baran decarboxylative coupling and a Friedel-Crafts cyclization/olefin isomerization/aromatization cascade that rapidly assembled the tetracyclic core framework. This synthetic strategy is expected to be readily amenable to the synthesis of other phenolic steroids.

An approach to functionalized carbazoles from Z-enoate propargylic alcohols. A unified total synthesis of N-Me-carazostatin, N-Me-carbazoquinocin C and N-Me-lipocarbazole A4

Development of an acid catalyzed, intramolecular benzannulation of indoles for the synthesis of functionalized carbazoles has been reported. The indole appended Z-enoate propargylic alcohols have been employed. The N-EDG-indoles involve the 5-exo-dig cyclization followed by 1,2-migration to give the carbazole-butenoates, whereas the N-EWG-indoles undergo the Z-enoate assisted Meyer-Schuster rearrangement to give the dihydrocarbazole-4-oxo-butanoates. Utilizing one of the 2-methyl-carbazole-butyraldehyde (obtained from the corresponding carbazole-butanoate) as the key intermediate, we have developed a simple approach for an efficient synthesis of N-Me-carazostatin, N-Me-carbazoquinocin C and N-Me-lipocarbazole A4.

Simple and Practical Conversion of Benzoic Acids to Phenols at Room Temperature

Phenols are important organic molecules because they have found widespread applications in many fields. Herein, an efficient and practical approach to prepare phenols from benzoic acids via simple organic reagents at room temperature is reported. This approach is compatible with various functional groups and heterocycles and can be easily scaled up. To demonstrate its synthetic utility, bioactive molecules and unsymmetrical hexaarylbenzenes have been prepared by leveraging this transformation as strategic steps. Mechanistic investigations suggest that the key migration step involves a free carbocation instead of a radical intermediate. Considering the abundance of benzoic acids and the utility of phenols, it is anticipated that this method will find broad applications in organic synthesis.

Oxalamide/Amide Ligands: Enhanced and Copper-Catalyzed C-N Cross-Coupling for Triarylamine Synthesis

Triarylamines are privileged core structures that are found in versatile optoelectronic materials. New methods are constantly being sought for their preparation. Herein, a new protocol for triarylamine synthesis is presented where a wide range of diarylamines couple smoothly with aryl bromides mediated by a copper oxalamide (or amide) catalytic system. Notably, a new non-C₂-symmetric 1-isoquinolinamide-based N,N-/N,O-bidentate ligand was introduced that could tolerate bulky diarylamines. Plenty of known optoelectronic functional molecules could be synthesized in good to excellent yields. The practicality of this C-N cross-coupling was illustrated by the gram-scale synthesis of a patented thermally activated delayed fluorescence emitter for organic light-emitting diodes.

Organocatalytic Synthesis of Phenols from Diaryliodonium Salts with Water under Metal-Free Conditions

The metal-free synthesis of phenols from diaryliodonium salts with water was developed by using N-benzylpyridin-2-one as an organocatalyst. In this process, sterically congested, functionalized, and heterocycle-containing iodonium salts were smoothly converted to the desired products, and the clofibrate and mecloqualone derivatives were also synthesized in high yields. In addition, the gram-scale experiment was successfully carried out with 10 mmol of a sterically congested substrate.

Visible-Light Copper Nanocluster Catalysis for the C-N Coupling of Aryl Chlorides at Room Temperature

Activation of aryl chlorides in cross-coupling reactions is a long-standing challenge in organic synthesis that is of great interest to industry. Ultrasmall (<3 nm), atomically precise nanoclusters (NCs) are considered one of the most promising catalysts due to their high surface area and unsaturated active sites. Herein, we introduce a copper nanocluster-based catalyst, [Cu₆₁(S^tBu)₂₆S₆Cl₆H₁₄] (Cu₆₁NC) that enables C-N bond-forming reactions of aryl chlorides under visible-light irradiation at room temperature. A range of N-heterocyclic nucleophiles and electronically and sterically diverse aryl/hetero chlorides react in this new Cu₆₁NC-catalyzed process to afford the C-N coupling products in good yields. Mechanistic studies indicate that a single-electron-transfer (SET) process between the photoexcited Cu₆₁NC complex and aryl halide enables the C-N-arylation reaction.

Chasing Self-Assembly of Thioether-Substituted Flavylium Salts in Solution and Bulk State

Two series of flavylium triflates carrying alkoxy side chains in the A‐ring (benzo unit of chromylium salt) and thioethers in the B ring (phenyl unit) (O_n‐Fla‐S_m) as well as thioethers at both A and B ring (S_n‐Fla‐S_m) were synthesized in order to understand the effect of thioether functionalization on their self‐assembly and electronic properties. Concentration‐dependent and diffusion ordered (DOSY) NMR experiments of O₁‐iV‐Fla‐S₃ indicate the formation of columnar H‐aggregates in solution with antiparallel intracolumnar stacking of the AC unit (chromylium) of the flavylium triflate, in agreement with the solid state structure of O₁‐V‐Fla‐S₁. Thioether substitution on the B ring changes the linear optical properties in solution, whereas it has no effect on the A ring. According to differential scanning calorimetry, polarizing optical microscopy and X‐ray diffraction bulk self‐assembly of these ionic liquid crystals (ILCs) depends on the total number of side chains, yielding SmA and Lam_Col phases for ILCs with 2–3 chains and Col_ro, Col_h phases for ILCs with 3–6 chains. Thus, we demonstrated that thioethers are a useful design tool for ILCs with tailored properties.

Chiral oxamide–phosphine–palladium catalyzed highly asymmetric allylic amination: carbonyl assistance for high regio- and enantiocontrols

The chiral oxamide–phosphine (COAP) ligands were developed for the palladium-catalyzed asymmetric allylic amination of vinyl benzoxazinones with alkylamines, affording a series of optically active diamines in good yields with high enantioselectivity.

Pd-Free synthesis of dithienothiophene-based oligoaryls for effective hole-transporting materials by optimized Cu-catalyzed annulation and direct C–H arylation

For the first time, [Cu]-catalyzed annulation and direct C–H/C–I couplings were used as key transformations to access new DTT-based hole-transporting materials (HTMs), CHC05–07. Perovskite solar cells with CHC07 display PCEs of up to 14.7%.

Copper-Catalyzed Ullmann-Type Coupling and Decarboxylation Cascade of Arylhalides with Malonates to Access α-Aryl Esters

We have developed a high-efficiency and practical Cu-catalyzed cross-coupling to directly construct versatile α-aryl-esters by utilizing readily available aryl bromides (or chlorides) and malonates. These gram-scale approaches occur with turnovers of up to 1560 and are smoothly conducted by the usage of a low catalyst loading, a new available ligand, and a green solvent. A variety of functional groups are tolerated, and the application occurs with α-aryl-esters to access nonsteroidal anti-inflammatory drugs (NSAIDs) on the gram scale.

para-Selective hydroxylation of alkyl aryl ethers

para-Selective hydroxylation of alkyl aryl ethers is established, which proceeds with a ruthenium(II) catalyst, hypervalent iodine(III) and trifluoroacetic anhydride via a radical mechanism. This protocol tolerates a wide scope of substrates and provides a facile and efficient method for preparing clinical drugs monobenzone and pramocaine on a gram scale.

Radical-anion coupling through reagent design: hydroxylation of aryl halides

The design and development of an oxime-based hydroxylation reagent, which can chemoselectively convert aryl halides (X = F, Cl, Br, I) into phenols under operationally simple, transition-metal-free conditions is described. Key to the success of this approach was the identification of a reducing oxime anion which can interact and couple with open-shell aryl radicals. Experimental and computational studies support the proposed radical-nucleophilic substitution chain mechanism.