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The identification of reliable, general, and high yielding methods for the formation of C(sp

This communication reports a method for the vinylogous radiofluorination of α-diazoacetates to generate γ-[(18)F]fluoro-α,β-unsaturated esters and ketones in moderate to good radiochemical yields. The method uses no-carrier-added [(18)F]AgF and is compatible with aromatic and non-aromatic substrates and a number of different functional groups. The labeling method is showcased in the synthesis of a fluorinated 5-cholesten-3-one derivative as well as a difluorinated product pertinent to drug discovery.

A Cu-mediated ortho-C-H radiofluorination of aromatic carboxylic acids that are protected as 8-aminoquinoline benzamides is described. The method uses K18 F and is compatible with a wide range of functional groups. The reaction is showcased in the high specific activity automated synthesis of the RARβ2 agonist [18 F]AC261066.

This article describes a detailed investigation of ligand effects on Ph–CF3 coupling from phosphinoferrocene-ligated PdII(Ph)(CF3) complexes. This study reveals that increasing the size of the phosphine substituents results in an enhanced rate of Ph–CF3 coupling, with (DtBPF)Pd(Ph)(CF3) (DtBPF = 1,1′-bis(di-tert-butylphosphino)ferrocene) being the most reactive complex. The mechanism of Ph–CF3 bond formation from both (DtBPF)Pd(Ph)(CF3) and (DiPrPF)Pd(Ph)(CF3) (DiPrPF = 1,1′-bis(diisopropylphosphino)ferrocene) was interrogated experimentally and computationally. These studies implicate a pathway involving concerted Ph–CF3 bond-forming reductive elimination from the four-coordinate PdII centers. An alternative pathway involving α-fluoride elimination and subsequent PhF2C–F coupling from PdII(CF2Ph)(F) intermediates was also evaluated but was ruled out based on DFT as well as the independent synthesis and reactivity studies of (DiPrPF)Pd(CF2Ph)(F).

A highly reducing diquat-type molecule was explored as a negative electrolyte for nonaqueous redox flow batteries. The molecule displays a highly negative 2+/0 reduction potential of −1.67 V (vs. ferrocene), a low mass per electron transferred, and good solubility in CH3CN in both redox states. Moderate capacity retention is observed during electrochemical charge–discharge cycling. A pathway for decomposition during electrochemical cycling is elucidated, and this provides a clear path forward for enhancing stability.

This report describes a Pd-mediated C–H radiofluorination of 8-methylquinoline derivatives with no-carrier-added Ag[18F]F. To achieve this transformation, a new method was developed for the generation of Ag[18F]F using a sep-pak cartridge. The C–H radiofluorination was then optimized and applied to a series of substituted 8-methylquinoline derivatives. Finally, this method was fully automated using a radiochemistry synthesis module.

A simple technique for the preparation of [18F]HF has been developed and applied to the generation of an [18F]FeF species for opening sterically hindered epoxides. This method has been successfully employed to prepare four drug-like molecules, including 5-[18F]fluoro-6-hydroxy-cholesterol, a potential adrenal/endocrine PET imaging agent. This easily automated one-pot procedure produces sterically hindered fluorohydrin PET imaging agents in good yields and high molar activities.

This Letter describes the development of a TiIII-mediated reaction for the C–H amination of arenes with hydroxylamine. This reaction is applied to a variety of electron-rich (hetero)arene substrate...

The reaction of carboxylic acid derivatives with amines to form amide bonds has been the most widely used transformation in organic synthesis over the past century. Its utility is driven by the broad availability of the starting materials as well as the kinetic and thermodynamic driving force for amide bond formation. As such, the invention of new reactions between carboxylic acid derivatives and amines that strategically deviate from amide bond formation remains both a challenge and an opportunity for synthetic chemists. This report describes the development of a nickel-catalyzed decarbonylative reaction that couples (hetero)aromatic esters with a broad scope of amines to form (hetero)aryl amine products. The successful realization of this transformation was predicated on strategic design of the cross-coupling partners (phenol esters and silyl amines) to preclude conventional reactivity that forms inert amide by-products.

This report describes a Pd-mediated C-H radiofluorination of 8-methylquinoline derivatives with no-carrier-added Ag[(18)F]F. To achieve this transformation, a new method was developed for the generation of Ag[(18)F]F using a sep-pak cartridge. The C–H radiofluorination was then optimized and applied to a series of substituted 8-methylquinoline derivatives. Finally, this method was fully automated using a radiochemistry synthesis module.

Copper-mediated 11C-cyanation reactions have enabled the synthesis of PET radiotracers from a range of readily available precursors and avoid the need to use more toxic Pd catalysts. In this work we adapt our recently developed 11C-cyanation of arylpinacolboronate (BPin) esters for the cGMP synthesis of [11C]LY2795050, a selective antagonist radiotracer for the kappa opioid receptor (KOR). [11C]LY2795050 was synthesized in 6 ± 1% noncorrected radiochemical yield (based on [11C]HCN, n = 3) using an automated synthesis module. Quality control testing confirmed the suitability of doses for preclinical and clinical PET imaging (radiochemical purity >99%; specific activity >900 mCi/μmol; residual Cu < 0.1 μg/mL). PET imaging was conducted in rodent and nonhuman primates, showing good brain uptake of [11C]LY2795050 and the expected distribution of KOR. Analogous imaging with [11C]carfentanil (a selective mu opioid receptor (MOR) radiotracer) revealed the anticipated regional differences in MOR and KOR distribution in the primate brain.

The Suzuki–Miyaura cross-coupling of organoboron nucleophiles with aryl halide electrophiles is one of the most widely used carbon–carbon bond-forming reactions in organic and medicinal chemistry1,2. A key challenge associated with these transformations is that they generally require the addition of an exogenous base, the role of which is to enable transmetallation between the organoboron nucleophile and the metal catalyst3. This requirement limits the substrate scope of the reaction because the added base promotes competitive decomposition of many organoboron substrates3–5. As such, considerable research has focused on strategies for mitigating base-mediated side reactions6–12. Previous efforts have primarily focused either on designing strategically masked organoboron reagents (to slow base-mediated decomposition)6–8 or on developing highly active palladium precatalysts (to accelerate cross-coupling relative to base-mediated decomposition pathways)10–12. An attractive alternative approach involves identifying combinations of catalyst and electrophile that enable Suzuki–Miyaura-type reactions to proceed without an exogenous base12–14. Here we use this approach to develop a nickel-catalysed coupling of aryl boronic acids with acid fluorides15–17, which are formed in situ from readily available carboxylic acids18–22. This combination of catalyst and electrophile enables a mechanistic manifold in which a ‘transmetallation-active’ aryl nickel fluoride intermediate is generated directly in the catalytic cycle13,16. As such, this transformation does not require an exogenous base and is applicable to a wide range of base-sensitive boronic acids and biologically active carboxylic acids. This nickel-catalysed Suzuki–Miyaura coupling of aryl boronic acids with in-situ-generated acid fluorides does not require an exogenous base and is applicable to a range of base-sensitive boronic acids and bioactive carboxylic acids.

This report describes the synthesis of model complexes for key intermediates in the Pd-catalyzed transannular C(sp(3))–H arylation of alicyclic amines. These complexes react stoichiometrically with phenyl iodide to afford C–H arylation products. Furthermore, they participate in H/D exchange with d(10)-tert-butanol at temperatures as low as 40 °C. Overall, these studies provide insights into the factors controlling transannular C(sp(3))–H activation in these systems. [Image: see text]

This paper describes a detailed study of the deoxyfluorination of aryl fluorosulfonates with tetramethylammonium fluoride (NMe4F) and ultimately identifies other sulfonate electrophiles that participate in this transformation. 19F NMR spectroscopic monitoring of the deoxyfluorination of aryl fluorosulfonates revealed the rapid formation of diaryl sulfates under the reaction conditions. These intermediates can proceed to fluorinated products; however, diaryl sulfate derivatives bearing electron-donating substituents react very slowly with NMe4F. Based on these findings, aryl triflate and aryl nonaflate derivatives were explored, since these cannot react to form diaryl sulfates. Aryl triflates were found to be particularly effective electrophiles for deoxyfluorination with NMe4F, and certain derivatives (i.e., those bearing electron-neutral/donating substituents) afforded higher yields than their aryl fluorosulfonate counterparts. Computational studies implicate a similar mechanism for deoxyfluorination of ...

This Article describes the development of a second-generation catalyst system for the transannular C–H functionalization of alicyclic amines. Pyridine- and quinoline-carboxylate ligands are shown to be highly effective for increasing the reaction rate, yield, and scope of Pd-catalyzed transannular C–H arylation reactions of azabicyclo[3.1.0]hexane, azabicyclo[3.1.1]heptane, azabicyclo[3.2.1]octane, and piperidine derivatives. Mechanistic studies reveal that the pyridine/quinoline-carboxylates play a role in impeding both reversible and irreversible catalyst decomposition pathways. These ligands enable the first reported examples of the transannular C–H arylation of the ubiquitous tropane, 7-azanorbornane, and homotropane cores. Finally, the pyridine/quinoline-carboxylates are shown to promote both transannular C–H arylation and transannular C–H dehydrogenation on a homotropane substrate.

A copper-mediated method for the transformation of diverse arylboron compounds and arylstannanes to aryl-[11C]-nitriles is reported. This method is operationally simple, uses commercially available reagents, and is compatible with a wide variety of substituted aryl- and heteroaryl substrates. This method is applied to the automated synthesis of high specific activity [11C]perampanel in 10% nondecay-corrected radiochemical yield (RCY).

This paper describes the systematic study of metal–organic framework (MOF) catalysts for the reaction of propylene oxide (PO) with carbon dioxide (CO2) to generate propylene carbonate (PC). These studies began with the evaluation of MIL-101(Cr) as catalyst in a flow reactor. Under the developed flow conditions, MIL-101(Cr) was found to effectively catalyze PO carbonation in the absence of a halide co-catalyst. A systematic study of catalyst performance was then undertaken as a function of MOF synthesis technique, activation conditions, metal center, and node architecture. Ultimately, these investigations led to the identification of MIL-100(Sc) as a new, active, and stable catalyst for PO carbonation.

This Letter describes the development of a method for the Pd-catalyzed electrochemical acetoxylation of C–H bonds. The oxidation step of the catalytic cycle is probed through cyclic voltammetry and bulk electrolysis studies of a pre-formed palladacycle of 8-methylquinoline. A catalytic system for C–H acetoxylation is then developed and optimized with respect to the cell configuration, rate of oxidation, and chemistry at the counter electrode. This transformation is then applied to substrates containing various directing groups and to the acetoxylation of both C(sp2)–H and C(sp3)–H bonds.

Aqueous redox flow batteries (RFBs) can serve as inexpensive grid-scale energy storage devices. A key challenge for developing these systems is identifying storage materials that undergo reversible redox events at potentials near the voltaic limits of aqueous media. This work details the development of a benzoylpyridinium-based anolyte for this application. A combination of electrochemical and spectroscopic studies guided the selection of a supporting electrolyte to mitigate anolyte-catalyzed proton reduction at the low potentials. These insights were used to achieve stable one-electron cycling with KOH as the support in both a H cell and in a laboratory-scale flow cell. In the latter experiment, cycling versus iron ferrocyanide afforded an aqueous RFB with an open-circuit voltage exceeding 1 V.

This article describes a detailed comparison of the organometallic chemistry of high-valent nickel and palladium model complexes supported by tris(pyrazolyl)borate and cycloneophyl ligands. The accessibility of the MIII and MIV oxidation states with each metal is investigated through electrochemical and chemical oxidation of the MII precursors. These studies show that the NiII precursor readily undergoes both one- and two-electron oxidations to generate stable NiIII and NiIV products. In contrast, under the conditions examined, the PdII analogue undergoes exclusively two-electron-oxidation reactions to form PdIV. Reactivity studies of isolated NiIV and PdIV complexes show that both participate in C(sp3)–heteroatom coupling reactions and that the reactions at NiIV are approximately 2 orders of magnitude faster than those at PdIV. Experimental and computational mechanistic studies implicate outer-sphere SN2-type pathways for these processes. With most nucleophiles (e.g., phenoxide, acetate, thiophenoxide), ...

This report describes a method for Pd-catalyzed decarbonylative cross-coupling that enables the conversion of carboxylic acid derivatives to biaryls, aryl amines, aryl ethers, aryl sulfides, aryl boronate esters, and trifluoromethylated arenes. The success of this transformation leverages the Pd0/Brettphos-catalyzed decarbonylative chlorination of aroyl chlorides, which can then participate in diverse cross-coupling reactions in situ using the same Pd catalyst.

This communication describes a method for the nucleophilic radiofluorination of electron-rich arenes. The reaction involves the initial C(sp2)–H functionalization of an electron-rich arene with MesI(OH)OTs to form a (mesityl)(aryl)iodonium salt. This salt is then used in situ in a Cu-mediated radiofluorination with [18F]KF. This approach leverages the stability and availability of electron-rich arene starting materials to enable mild late-stage radiofluorination of toluene, anisole, aniline, pyrrole, and thiophene derivatives. The radiofluorination has been automated to access a 41 mCi dose of an 18F-labeled nimesulide derivative in high (2800 ± 700 Ci/mmol) specific activity.

This article focuses on the development of practical approaches to the in situ generation of anhydrous fluoride salts for applications in nucleophilic aromatic substitution (SNAr) reactions. We report herein that a variety of combinations of inexpensive nucleophiles (e.g., tetraalkylammonium cyanide and phenoxide salts) and fluorine-containing electrophiles (e.g., acid fluoride, fluoroformate, benzenesulfonyl fluoride, and aryl fluorosulfonate derivatives) are effective for this transformation. Ultimately, we demonstrate that the combination of tetramethylammonium 2,6-dimethylphenoxide and sulfuryl fluoride (SO2F2) serves as a particularly practical route to anhydrous tetramethylammonium fluoride. This procedure is applied to the SNAr fluorination of a range of electron-deficient aryl and heteroaryl chlorides as well as nitroarenes.

Difluoromethyl copper complexes have been proposed as key intermediates in a variety of Cu-catalyzed difluoromethylation reactions. However, studies of these putative intermediates have been impeded by the low stability of these [Cu(CHF2)] species. This report describes the synthesis of isolable N-heterocyclic carbene ligated copper(I) difluoromethyl complexes. The stoichiometric reactions of these complexes with aryl electrophiles (i.e., diaryliodonium salts, aryl iodides, and aryl bromides) are described. In addition, N-heterocyclic carbene copper(I) species are demonstrated to serve as catalysts for the cross-coupling of aryl iodides with (difluoromethyl)trimethylsilane to afford difluoromethyl arene products.

This Article demonstrates a mild oxidatively induced C(sp

This Article describes the development of a base-free, nickel-catalyzed decarbonylative coupling of carboxylic acid fluorides with diboron reagents to selectively afford aryl boronate ester products. Detailed studies were conducted to assess the relative rates of direct transmetalation between aryl boronate esters and diboron reagents and a bisphosphine nickel(aryl)(fluoride) intermediate. These investigations revealed that diboron reagents undergo transmetalation with this Ni(aryl)(fluoride) intermediate at rates significantly faster than their aryl boronate ester congeners. Furthermore, the reactivity of both boron reagents toward transmetalation is enhanced with increasing electrophilicity of the boron center. These mechanistic insights were leveraged to develop a catalytic decarbonylative borylation of acid fluorides that proved applicable to a variety of (hetero)aryl carboxylic acid fluorides as well as diverse diboron reagents. The acid fluorides can be generated

This Article describes the synthesis and characterization of cyclometalated aminoquinoline Ni

A one-pot two-step synthesis of 6-[(18)F]fluoro-L-DOPA ([(18)F]FDOPA) has been developed involving Cu-mediated radiofluorination of a pinacol boronate ester precursor. The method is fully automated, provides [(18)F]FDOPA in good activity yield (104 ± 16 mCi, 6 ± 1%), excellent radiochemical purity (>99%) and high molar activity (3799 ± 2087 Ci/mmol), n=3, and has been validated to produce the radiotracer for human use.

[(18)F]6-Fluoro-L-DOPA ([(18)F]FDOPA), is used for diagnostic PET imaging. Using this protocol, radiofluorination of the electron-rich catechol ring can be achieved in the presence of the amino acid group by Cu-mediated fluorination of a pinacol boronate precursor. [(18)F]6-Fluoro-L-DOPA ([(18)F]FDOPA) is a diagnostic radiopharmaceutical for positron emission tomography (PET) imaging that is used to image Parkinson’s disease, brain tumors, and focal hyperinsulinism of infancy. Despite these important applications, [(18)F]FDOPA PET remains underutilized because of synthetic challenges associated with accessing the radiotracer for clinical use, stemming from the need to radiofluorinate a highly electron rich catechol ring in the presence of an amino acid. To address this longstanding challenge in the PET radiochemistry community, we have developed a one-pot, two-step synthesis of high molar activity [(18)F]FDOPA by Cu-mediated fluorination of a pinacol boronate (BPin) precursor. The method is fully automated, has been validated to work well at two separate sites (an academic facility with a cyclotron on site and an industry lab purchasing [(18)F]fluoride from an outside vendor), and provides [(18)F]FDOPA in reasonable radiochemical yield (2.44 ± 0.70 GBq, 66 ± 19 mCi, 5 ± 1%), excellent radiochemical purity (>98%) and high molar activity (76 ± 30 TBq/mmol, 2050 ± 804 Ci/mmol), n=26. Herein we report a detailed protocol for the synthesis of [(18)F]FDOPA which has been successfully implemented at two sites and validated for production of the radiotracer for human use.

The implementation of redox active organics in nonaqueous redox flow batteries requires the design of molecules that exhibit high solubility (>1 M) in all battery-relevant redox states. Methods for forecasting nonaqueous solubility would be valuable for streamlining the identification of promising structures. Herein we report the development of a workflow to parametrize and predict the solubility of conformationally flexible tris-(dialkylamino)cyclopropenium (CP) radical dications. A statistical model is developed through training on monomer species. Ultimately, this model is used to predict new monomeric and dimeric CP derivatives with solubilities of >1 M in acetonitrile in all oxidation states. The most soluble CP monomer exhibits high stability to electrochemical cycling at 1 M in acetonitrile without a supporting electrolyte in a symmetrical flow cell.

A simple technique for the preparation of [(18)F]HF has been developed and applied to the generation of an [(18)F]FeF species for opening sterically hindered epoxides. This method has been successfully employed to prepare four drug-like molecules, including 5-[(18)F]fluoro-6-hydroxy-cholesterol, a potential adrenal/endocrine PET imaging agent. This easily automated one-pot procedure produces sterically hindered fluorhydrin PET imaging agents in good yields and high molar activities.

Described is a systematic comparison of factors impacting the relative rates and selectivities of C(sp3 )-C and C(sp3 )-O bond-forming reactions at high-valent Ni as a function of oxidation state. Two Ni complexes are compared: a cationic octahedral NiIV complex ligated by tris(pyrazolyl)borate and a cationic octahedral NiIII complex ligated by tris(pyrazolyl)methane. Key features of reactivity/selectivity are revealed: 1) C(sp3 )-C(sp2 ) bond-forming reductive elimination occurs from both centers, but the NiIII complex reacts up to 300-fold faster than the NiIV , depending on the reaction conditions. The relative reactivity is proposed to derive from ligand dissociation kinetics, which vary as a function of oxidation state and the presence/absence of visible light. 2) Upon the addition of acetate (AcO- ), the NiIV complex exclusively undergoes C(sp3 )-OAc bond formation, while the NiIII analogue forms the C(sp3 )-C(sp2 ) coupled product selectively. This difference is rationalized based on the electrophilicity of the respective M-C(sp3 ) bonds, and thus their relative reactivity towards outer-sphere SN 2-type bond-forming reactions.

A palladium-catalyzed cross-coupling of aryl chlorides/bromides with TMSCF

A method for the room temperature deoxyfluorination of benzaldehydes and α-ketoesters using sulfuryl fluoride and Me4NF is described. A large scope of aryl and heteroaryl substrates is demonstrated, and this method compares favorably to other common deoxyfluorination methods for many substrates.

This report describes a method for the deoxyfluorination of phenols with sulfuryl fluoride (SO2F2) and tetramethylammonium fluoride (NMe4F) via aryl fluorosulfonate (ArOFs) intermediates. We first demonstrate that the reaction of ArOFs with NMe4F proceeds under mild conditions (often at room temperature) to afford a broad range of electronically diverse and functional group-rich aryl fluoride products. This transformation was then translated to a one-pot conversion of phenols to aryl fluorides using the combination of SO2F2 and NMe4F. Ab initio calculations suggest that carbon–fluorine bond formation proceeds via a concerted transition state rather than a discrete Meisenheimer intermediate.

This letter describes the development of a method for selective remote C(sp3)–H oxygenation of protonated aliphatic amines using aqueous potassium persulfate. Protonation serves to deactivate the proximal C(sp3)–H bonds of the amine substrates and also renders the amines soluble in the aqueous medium. These reactions proceed under relatively mild conditions (within 2 h at 80 °C with amine as limiting reagent) and do not require a transition metal catalyst. This method is applicable to a variety of types of C(sp3)–H bonds, including 3°, 2°, and benzylic C–H sites in primary, secondary, and tertiary amine substrates.

This report describes a computational study of C(sp3)–OR bond formation from PdIV complexes of general structure PdIV(CH2CMe2-o-C6H4-C,C′)(F)(OR)(bpy-N,N′) (bpy = 2,2′-bipyridine). Dissociation of −OR from the different octahedral PdIV starting materials results in a common square-pyramidal PdIV cation. An SN2-type attack by −OR (−OR = phenoxide, acetate, difluoroacetate, and nitrate) then leads to C(sp3)–OR bond formation. In contrast, when −OR = triflate, concerted C(sp3)–C(sp2) bond-forming reductive elimination takes place, and the calculations indicate this outcome is the result of thermodynamic rather than kinetic control. The energy requirements for the dissociation and SN2 steps with different −OR follow opposing trends. The SN2 transition states exhibit “Pd⋯C⋯O” angles in a tight range of 151.5 to 153.0°, resulting from steric interactions between the oxygen atom and the gem-dimethyl group of the ligand. Conformational effects for various OR ligands and isomerisation of the complexes were also examined as components of the solution dynamics in these systems. In all cases, the trends observed computationally agree with those observed experimentally.

This communication describes the synthesis of an organometallic NiIV complex bearing a labile trifluoroacetate (OTFA) ligand via the oxidation of a NiII precursor with PhI(OTFA)2. Intramolecular C(sp2)–O bond-forming reductive elimination from this NiIV complex is relatively slow, requiring 6 h at 70 °C to reach completion. In contrast, transmetalation with TMSCF3 occurs within just 1 h at room temperature to generate a NiIV–CF3 complex. These studies show that intermolecular reactions such as transmetalation can be competitive with intramolecular reductive elimination processes at NiIV centers.

A copper-mediated nucleophilic radiofluorination of aryl- and vinylstannanes with [18F]KF is described. This method is fast, uses commercially available reagents, and is compatible with both electron-rich and electron-deficient arene substrates. This method has been applied to the manual synthesis of a variety of clinically relevant radiotracers including protected [18F]F-phenylalanine and [18F]F-DOPA. In addition, an automated synthesis of [18F]MPPF is demonstrated that delivers a clinically validated dose of 200 ± 20 mCi with a high specific activity of 2400 ± 900 Ci/mmol.

This article describes the iron-catalyzed hydrogenation of unactivated amides. Under the optimal conditions, a PNP-ligated Fe catalyst affords 25–300 turnovers of products derived from C–N bond cleavage. This reaction displays a broad substrate scope, including a variety of 2° and 3° amide substrates. The reaction progress of N,N-dimethylformamide hydrogenation has been monitored in situ using Raman spectroscopy. This technique enables direct comparison of the relative activity of the Fe-PNP catalyst to that of its Ru analogue. Under otherwise identical conditions, the Fe and Ru catalysts exhibit rates within a factor of 2.

This paper describes the Cu(OTf)2-mediated coupling of aryl and heteroaryl trifluoroborates with tetrabutylammonium or alkali metal salts to form C–O, C–N, and C–halogen bonds. The reactions proceed under mild conditions (often room temperature over 16 hours) with carboxylate, halide, and azide salts, all nucleophiles that have been underrepresented in the copper cross-coupling literature. Preliminary results show that copper salts bearing weakly coordinating X-type ligands are essential for enabling these transformations to proceed under mild conditions.

Silver carboxylate salts are widely used as additives in palladium-catalyzed C–H functionalization reactions. However, the role of these silver additives is often not fully understood. This paper describes an investigation of the role of AgOPiv in the stoichiometric activation of C6F5H at a well-defined PdII complex as well as in the PdII-catalyzed oxidative dimerization of 2-alkylthiophenes. Both in situ NMR spectroscopy and H/D exchange studies of the reactions of C6F5H implicate a role for AgOPiv in the C–H cleavage event, generating Ag–C6F5 as an intermediate. The catalytic studies show similar trends despite the different conditions and substrates, suggesting that AgOPiv promotes a similar metalation of the thiophene in the catalytic transformations. This proposal is supported by DFT calculations, which show energetically feasible pathways for concerted metalation–deprotonation of both 2-methylthiophene and pentafluorobenzene at [Ag(OPiv)]2. These studies suggest that initial metalation of C–H substr...

The cationic rhodium complexes (dppe)Rh(COD)BF4 and (MeCN)2Rh(COD)BF4 have been supported in metal–organic frameworks bearing anionic nodes (ZJU-28) and anionic linkers (MIL-101-SO3) via ion exchange. These MOF-supported Rh species serve as recyclable catalysts for the hydrogenation of both the terminal alkene substrate 1-octene and the internal alkene substrate 2,3-dimethylbutene. The nature of the MOF support impacts various aspects of catalysis, including: (i) the rate of 1-octene hydrogenation, (ii) the activity and recyclability of the catalyst in 2,3-dimethylbutene hydrogenation, and (iii) the size selectivity of hydrogenation with alkene substrates appended to calixarenes.

Half-sandwich iridium bipyridine complexes catalyze the hydrogenation of esters and lactones under base-free conditions. The reactions proceed with a variety of ester and lactone substrates. Mechanistic studies implicate a pathway involving rate-limiting hydride transfer to the substrate at high pressures of H2 (≥50 bar).

Methane borylation in a cyclohexane sea Although methane combusts readily at high temperatures, it is generally the hardest hydrocarbon to transform under gentler conditions, owing to its particularly strong C-H bonds. Cook et al. now show that soluble rhodium, iridium, and ruthenium catalysts can slice through these C-H bonds to add boron substituents to methane at 150°C. Smith et al. report the iridium-catalyzed reaction using phosphine ligands to enhance activity. Both studies were performed in cyclohexane solvent, revealing a remarkable selective preference for the methane reaction over functionalization of the cyclic hydrocarbon. Science , this issue pp. 1421 and 1424