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In the past, Cu‐oxo or ‐hydroxy clusters hosted in zeolites have been suggested to enable the selective conversion of methane to methanol, but the impact of the active site's stoichiometry and structure on methanol production is still poorly understood. Herein, we apply theoretical modeling in conjunction with experiments to study the impact of these two factors on partial methane oxidation in the Cu‐exchanged zeolite SSZ‐13. Phase diagrams developed from first‐principles suggest that Cu‐hydroxy or Cu‐oxo dimers are stabilized when O2 or N2O are used to activate the catalyst, respectively. We confirm these predictions experimentally and determine that in a stepwise conversion process, Cu‐oxo dimers can convert twice as much methane to methanol compared to Cu‐hydroxyl dimers. Our theoretical models rationalize how Cu‐di‐oxo dimers can convert up to two methane molecules to methanol, while Cu‐di‐hydroxyl dimers can convert only one methane molecule to methanol per catalytic cycle. These findings imply that in Cu clusters, at least one oxo group or two hydroxyl groups are needed to convert one methane molecule to methanol per cycle. This simple structure–activity relationship allows to intuitively understand the potential of small oxygenated or hydroxylated transition metal clusters to convert methane to methanol. [ABSTRACT FROM AUTHOR] more...

A simple and efficient nitrile-directed meta-C-H olefination, acetoxylation, and iodination of biaryl compounds is reported. Compared to the previous approach of installing a complex U-shaped template to achieve a molecular U-turn and assemble the large-sized cyclophane transition state for the remote C-H activation, a synthetically useful phenyl nitrile functional group could also direct remote meta-C-H activation. This reaction provides a useful method for the modification of biaryl compounds because the nitrile group can be readily converted to amines, acids, amides, or other heterocycles. Notably, the remote meta-selectivity of biphenylnitriles could not be expected from previous results with a macrocyclophane nitrile template. DFT computational studies show that a ligand-containing Pd-Ag heterodimeric transition state (TS) favors the desired remote meta-selectivity. Control experiments demonstrate the directing effect of the nitrile group and exclude the possibility of non-directed meta-C-H activation. Substituted 2-pyridone ligands were found to be key in assisting the cleavage of the meta-C-H bond in the concerted metalation-deprotonation (CMD) process. more...

We report a dynamic kinetic resolution (DKR) of chiral 4-pentenals by olefin hydroacylation. A primary amine racemizes the aldehyde substrate via enamine formation and hydrolysis. Then, a cationic rhodium catalyst promotes hydroacylation to generate α,γ-disubstituted cyclopentanones with high enantio- and diastereoselectivities. more...

peri-Disubstituted naphthalenes exhibit interesting physical properties and unique chemical reactivity, due to the parallel arrangement of the bonds to the two peri-disposed substituents. Regioselective installation of a functional group at the position peri to 1-substituted naphthalenes is challenging due to the steric interaction between the existing substituent and the position at which the second one would be installed. We report an iridium-catalyzed borylation of the C-H bond peri to a silyl group in naphthalenes and analogous polyaromatic hydrocarbons. The reaction occurs under mild conditions with wide functional group tolerance. The silyl group and the boryl group in the resulting products are precursors to a range of functional groups bound to the naphthalene ring through C-C, C-O, C-N, C-Br and C-Cl bonds. more...

The borylation of C-H bonds catalyzed by transition metals has been investigated extensively in the past two decades, but no iridium-catalyzed enantioselective borylation of C-H bonds has been reported. We report a set of iridium-catalyzed enantioselective borylations of aromatic C-H bonds. This reaction relies on a set of newly developed chiral quinolyl oxazoline ligands. This process proceeds under mild conditions with good to excellent enantioselectivity, and the borylated products can be converted to enantioenriched derivatives containing new C-O, C-C, C-Cl, or C-Br bonds. more...

Iridium catalysts containing dative nitrogen ligands are highly active for the borylation and silylation of C-H bonds, but chiral analogs of these catalysts for enantioselective silylation reactions have not been developed. We report a new chiral pyridinyloxazoline ligand for enantioselective, intramolecular silylation of symmetrical diarylmethoxy diethylsilanes. Regioselective and enantioselective silylation of unsymmetrical substrates was also achieved in the presence of this newly developed system. Preliminary mechanistic studies imply that C-H bond cleavage is irreversible, but not the rate-determining step. more...

Hydrosilyl ethers, generated in situ by the dehydrogenative silylation of cyclopropylmethanols with diethylsilane, undergo asymmetric, intramolecular silylation of cyclopropyl C-H bonds in high yields and with high enantiomeric excesses in the presence of a rhodium catalyst derived from a rhodium precursor and the bisphosphine (S)-DTBM-SEGPHOS. The resulting enantioenriched oxasilolanes are suitable substrates for the Tamao-Fleming oxidation to form cyclopropanols with conservation of the ee value from the C-H silylation. Preliminary mechanistic data suggest that C-H cleavage is likely to be the turnover-limiting and enantioselectivity-determining step. more...

We report a facile and powerful strategy to prepare libraries of oligothienoacene diimides that include anti‐ and syn‐isomers using palladium‐catalyzed C−H activation and an unexpected 1,2‐sulfur migration. Through this strategy, a series of oligothienoacene diimides containing 6, 8, and 10 fused rings were synthesized. The molecular geometry and extent of π‐conjugation have dramatic effects on the electronic properties, degree of crystallinity, and charge‐carrier transport properties. Notably, single‐crystal microfibers of syn‐3 c show electron mobilities up to 4.2 cm2 V−1 s−1, illustrating the significant potential of these materials for organic electronic devices. Our work demonstrates the versatility of this strategy for the development of oligothienoacene diimide libraries, in particular complex and large syn‐oligothienoacene diimides, which are difficult to prepare by present methods. [ABSTRACT FROM AUTHOR] more...

The asymmetric synthesis of ent-ketorfanol from simple and commercially available precursors is reported. A Rh(I) -catalyzed intramolecular CH alkenylation/torquoselective 6π electrocyclization cascade provides a fused bicyclic 1,2-dihydropyridine as a key intermediate. Computational studies were performed to understand the high torquoselectivity of the key 6π electrocyclization. The computational results demonstrate that a conformational effect is responsible for the observed selectivity. The ketone functionality and final ring are introduced in a single step by a redox-neutral acid-catalyzed rearrangement of a vicinal diol to give the requisite carbonyl, followed by intramolecular Friedel-Crafts alkylation. more...

Physicochemical properties constitute a key factor for the success of a drug candidate. Whereas many strategies to improve the physicochemical properties of small heterocycle-type leads exist, complex hydrocarbon skeletons are more challenging to derivatize because of the absence of functional groups. A variety of C-H oxidation methods have been explored on the betulin skeleton to improve the solubility of this very bioactive, yet poorly water-soluble, natural product. Capitalizing on the innate reactivity of the molecule, as well as the few molecular handles present on the core, allowed oxidations at different positions across the pentacyclic structure. Enzymatic oxidations afforded several orthogonal oxidations to chemical methods. Solubility measurements showed an enhancement for many of the synthesized compounds. more...

We report a versatile, highly enantioselective intramolecular hydrocarbonation reaction that provides a direct access to heteropolycyclic systems bearing chiral quaternary carbon stereocenters. The method, which relies on an iridium(I)/bisphosphine chiral catalyst, is particularly efficient for the synthesis of five‐, six‐ and seven‐membered fused indole and pyrrole products, bearing one and two stereocenters, with enantiomeric excesses of up to >99 %. DFT computational studies allowed to obtain a detailed mechanistic profile and identify a cluster of weak non‐covalent interactions as key factors to control the enantioselectivity. [ABSTRACT FROM AUTHOR] more...

The development of C(sp3)–H functionalizations of free carboxylic acids has provided a wide range of versatile C−C and C−Y (Y=heteroatom) bond‐forming reactions. Additionally, C–H functionalizations have lent themselves to the one‐step preparation of a number of valuable synthetic motifs that are often difficult to prepare through conventional methods. Herein, we report a β‐ or γ‐C(sp3)–H carbonylation of free carboxylic acids using Mo(CO)6 as a convenient solid CO source and enabled by a bidentate ligand, leading to convenient syntheses of cyclic anhydrides. Among these, the succinic anhydride products are versatile stepping stones for the mono‐selective introduction of various functional groups at the β position of the parent acids by decarboxylative functionalizations, thus providing a divergent strategy to synthesize a myriad of carboxylic acids inaccessible by previous β‐C–H activation reactions. The enantioselective carbonylation of free cyclopropanecarboxylic acids has also been achieved using a chiral bidentate thioether ligand [ABSTRACT FROM AUTHOR] more...

The palladium‐catalyzed [3+2] annulation of aromatic amides with maleimides via the activation of ortho benzylic C−H and meta C−H bonds is reported. Carboxamide and anilide type substrates that contain a 2‐methylthiophenyl group both participate in this [3+2] annulation, indicating that the presence of a 2‐methylthiophenyl directing group is a key for the success of the reaction. The first C−H bond activation at the benzylic C−H bond is followed by a second C−H bond activation at the meta C−H bond to give five‐membered cyclic products. The cleavage of these C−H bonds is irreversible. [ABSTRACT FROM AUTHOR] more...

This report discloses the photochemical homolytic cleavage of iodine azide after its formation following release from polymer‐bound bisazido iodate(I) anions. A series of radical reactions are reported including the 1,2‐functionlization of alkenes and the unprecedented chemoselective oxidation of secondary alcohols in the presence of primary alcohols. [ABSTRACT FROM AUTHOR] more...

Biaryl‐bridged cyclic peptides comprise an intriguing class of structurally diverse natural products with significant biological activity. Especially noteworthy are the antibiotics arylomycin and its synthetic analogue G0775, which exhibits potent activity against Gram‐negative bacteria. Herein, we present a simple, flexible, and reliable strategy based on activating‐group‐assisted catalytic oxidative coupling for assembling biaryl‐bridged cyclic peptides from natural amino acids. The synthetic approach was utilized for preparing a number of natural and unnatural biaryl‐bridged cyclic peptides, including arylomycin/G0775 and RP 66453 cyclic cores. [ABSTRACT FROM AUTHOR] more...

A cobalt-catalyzed chelation-assisted tandem C-H activation/C-C cleavage/C-H cyclization of arotic amides with alkylidenecyclopropanes is reported. This process allows the sequential formation of two C-C bonds, which is in sharp contrast to previous reports on using rhodium catalysts for the formation of C-N bonds. Here the inexpensive catalyst system exhibits good functional-group compatibility and relatively broad substrate scope. The desired products can be easily transformed into polycyclic lactones with m-CPBA. Mechanistic studies revealed that the tandem reaction proceeds through a C-H cobaltation, β-carbon elimination, and intramolecular C-H cobaltation sequence. [ABSTRACT FROM AUTHOR] more...

The first example of PdII‐catalyzed enantioselective C−H olefination with non‐chiral or racemic sulfoxides as directing groups was developed. A variety of chiral diaryl sulfoxides were synthesized with high enantioselectivity (up to 99 %) through both desymmetrization and parallel kinetic resolution (PKR). This is the first report of PdII‐catalyzed enantioselective C(sp2)−H functionalization through PKR, and it represents a novel strategy to construct sulfur chiral centers. [ABSTRACT FROM AUTHOR] more...

Syntheses of substituted anilines primarily rely on palladium-catalyzed coupling chemistry with prefunctionalized aryl electrophiles. While oxidative aminations have emerged as powerful alternatives, they largely produce undesired metal-containing by-products in stoichiometric quantities. In contrast, described herein is the unprecedented electrochemical C-H amination by cobalt-catalyzed C-H activation. The environmentally benign electrocatalysis avoids stoichiometric metal oxidants, can be conducted under ambient air, and employs a biomass-derived, renewable solvent for sustainable aminations in an atom- and step-economical manner with H2 as the sole byproduct. [ABSTRACT FROM AUTHOR] more...

A selective and mild method for the benzylic fluorination of aromatic azaheterocycles with Selectfluor is described. These reactions take place by a previously unreported mechanism, in which electron transfer from the heterocyclic substrate to the electrophilic fluorinating agent Selectfluor eventually yields a benzylic radical, thus leading to the desired C-F bond formation. This mechanism enables high intra- and intermolecular selectivity for aza-heterocycles over other benzylic components with similar C-H bond-dissociation energies. [ABSTRACT FROM AUTHOR] more...

Reported is a highly chemoselective intermolecular annulation of indole‐based biaryls with bromoalkyl alkynes by using palladium/norbornene (Pd/NBE) cooperative catalysis. This reaction is realized through a sequence of Catellani‐type C−H alkylation, alkyne insertion, and indole dearomatization, by forming two C(sp2)−C(sp3) and one C(sp2)−C(sp2) bonds in a single chemical operation, thus providing a diverse range of pentacyclic molecules, containing a spiroindolenine fragment, in good yields with excellent functional‐group tolerance. Preliminary mechanistic studies reveal that C−H bond cleavage is likely involved in the rate‐determining step, and the indole dearomatization might take place through an olefin coordination/insertion and β‐hydride elimination Heck‐type pathway. [ABSTRACT FROM AUTHOR] more...

A manganese(I)/Lewis acid cocatalyzed direct C−H propargylation with high selectivity has been developed. BPh3 was discovered to not only promote the reactivity, but also enhance the selectivity. Secondary, tertiary, and even quaternary carbon centers at the propargylic position could be directly constructed. Both internal and terminal alkynes are easily accessible. The chirality was successfully transferred from an axially chiral allene to central chirality. The reactivity of the manganese catalyst in this reaction was found to be unique among transition metal catalysts. [ABSTRACT FROM AUTHOR] more...

The conversion of methane into alcohols under moderate reaction conditions is a promising technology for converting stranded methane reserves into liquids that can be transported in pipelines and upgraded to value-added chemicals. We demonstrate that a catalyst consisting of small nickel oxide clusters supported on ceria-zirconia (NiO/CZ) can convert methane to methanol and ethanol in a single, steady-state process at 723 K using O2 as an abundantly available oxidant. The presence of steam is required to obtain alcohols rather than CO2 as the product of catalytic combustion. The unusual activity of this catalyst is attributed to the synergy between the small Lewis acidic NiO clusters and the redox-active CZ support, which also stabilizes the small NiO clusters. [ABSTRACT FROM AUTHOR] more...

Both aryl components of diaryliodonium salts can be used in a domino one-pot reaction via in situ generation of a directing group. A number of heterocycles undergo N-arylation which is followed by ruthenium-catalyzed C-arylation. Notably the reaction extends well to unsymmetrical diaryliodonium salts with a number of highly selective examples shown. [ABSTRACT FROM AUTHOR] more...

para-Selective C−H borylation of benzamides and pyridines has been achieved by cooperative iridium/aluminum catalysis. A combination of iridium catalysts commonly employed for arene C−H borylation and bulky aluminum-based Lewis acid catalysts provides an unprecedented strategy for controlling the regioselectivity of C−H borylation to give variously substituted (hetero)arylboronates, which are versatile synthetic intermediates for complex multi-substituted aromatic compounds. [ABSTRACT FROM AUTHOR] more...

Among the variety of isolable compounds with multiple bonds involving silicon, examples of compounds that contain silicon-boron double bonds (borasilenes) still remain relatively rare. Herein, we report the synthesis of the potassium salt of a chloride adduct of borasilene 1 ([ 2]−), which was obtained as an orange crystalline solid. Single-crystal X-ray diffraction analysis and reactivity studies on [ 2]− confirmed the double-bond character of the Si=B bond as well as the reduced Lewis acidity, which is due to the coordination of Cl− to the boron center. A thermal reaction of [ 2]− afforded a bicyclic product by formal intramolecular C−H insertion across the Si=B bond of 1, which was corroborated by a theoretical study. [ABSTRACT FROM AUTHOR] more...

The oxidative cross-coupling of aromatic substrates without the necessity of leaving groups or catalysts is described. The selective formation of partially protected nonsymmetric 2,2′-biphenols via electroorganic synthesis was accomplished with a high yield of isolated product. Since electric current is employed as the terminal oxidant, the reaction is reagent-free; no reagent waste is generated as only electrons are involved. The reaction is conducted in an undivided cell, and is suitable for scale-up and inherently safe. The implementation of O-silyl-protected phenols in this transformation results in both significantly enhanced yields and higher selectivity for the desired nonsymmetric 2,2′-biphenols. The use of a bulky silyl group to block one hydroxyl moiety makes the final product less prone to oxidation. Furthermore, the partially silyl-protected 2,2′-biphenols are versatile building blocks that usually require tedious or low-yielding synthetic pathways. Additionally, this strategy facilitates a large variety of new substrate combinations for oxidative cross-coupling reactions. [ABSTRACT FROM AUTHOR] more...

The synthesis of strophasterol A, a moderator of endoplasmatic reticulum (ER) stress in Alzheimer's disease, and the first member of a structurally unprecedented class of secosterols, was achieved through the implementation of a key step of its proposed biosynthesis and two C−H oxidations. Analysis of the innate reactivity of the intermediates enabled the identification of a novel way to prepare an α-chloro-γ-hydroxy-δ-keto enone, as well as its vinylogous α-ketol rearrangement to a δ-keto carboxylic acid. [ABSTRACT FROM AUTHOR] more...

Mononuclear nonheme high-spin (S=2) iron(IV)- oxo species have been identified as the key intermediates responsible for the C-H bond activation of organic substrates in nonheme iron enzymatic reactions. Herein we report that the C-H bond activation of hydrocarbons by a synthetic mononuclear nonheme high-spin (S=2) iron(IV)-oxo complex occurs through an oxygen non-rebound mechanism, as previously demonstrated in the C-H bond activation by nonheme intermediate (S=1) iron(IV)-oxo complexes. We also report that C-H bond activation is preferred over C=C epoxidation in the oxidation of cyclohexene by the nonheme high-spin (HS) and intermediate-spin (IS) iron(IV)-oxo complexes, whereas the C=C double bond epoxidation becomes a preferred pathway in the oxidation of deuterated cyclohexene by the nonheme HS and IS iron(IV)-oxo complexes. In the epoxidation of styrene derivatives, the HS and IS iron(IV) oxo complexes are found to have similar electrophilic characters. [ABSTRACT FROM AUTHOR] more...

A quinoline-based ligand effectively promotes the palladium-catalyzed borylation of C(sp3)¢H bonds. Primary β-C(sp³)-H bonds in carboxylic acid derivatives as well as secondary C(sp³)-H bonds in a variety of carbocyclic rings, including cyclopropanes, cyclobutanes, cyclopentanes, cyclohexanes, and cycloheptanes, can thus be borylated. This directed borylation method complements existing iridium(I)- and rhodium(I)-catalyzed C-H borylation reactions in terms of scope and operational conditions. [ABSTRACT FROM AUTHOR] more...

A novel palladium(II)-catalyzed [5+2] oxidative annulation of readily available o-arylanilines with alkynes has been developed for building a seven-membered N-heterocyclic architecture containing a biaryl linkage. This method is applicable to a wide range of unprotected o-arylanilines and internal alkynes, and results in the chemoselective preparation of imine-containing dibenzo[b,d]azepines in high yields with excellent diastereoselectivity with respect to the two types of stereogenic elements. [ABSTRACT FROM AUTHOR] more...

An efficient and selective Rh-catalyzed direct C-H functionalization reaction of enol phosphates was developed. The method is applicable to a variety of coupling partners, including activated alkenes, alkynes, and allenes, and leads to the formation of various valuable alkenylated and hydroalkenylated enol phosphates through the action of the phosphate directing group. The versatility and utility of the coupling products were demonstrated through further transformations into synthetically useful building blocks. [ABSTRACT FROM AUTHOR] more...

The rhodium(III)-catalyzed [3+2] C-H cyclization of aniline derivatives and internal alkynes represents a useful contribution to straightforward synthesis of indoles. However, there is no report on the more challenging synthesis of pharmaceutically important N-hydroxyindoles and 3H-indole- N-oxides. Reported herein is the first rhodium(III)- catalyzed [4+1] C-H oxidative cyclization of nitrones with diazo compounds to access 3H-indole-N-oxides. More significantly, this reaction proceeds at room temperature and has been extended to the synthesis of N-hydroxyindoles and N-hydroxyindolines. [ABSTRACT FROM AUTHOR] more...

A Ru-catalyzed direct C-H activation/meta-bromination of arenes bearing pyridyl, pyrimidyl, and pyrazolyl directing groups has been developed. A series of bromo aryl pyridines and pyrimidines have been synthesized, and further coupling reactions have also been demonstrated for a number of representative functionalized arenes. Preliminary mechanistic studies have revealed that this reaction may proceed through radical-mediated bromination when NBS is utilized as the bromine source. This type of transformation has opened up a new direction for the radical non-ipso functionalization of metal with regard to future C-H activation development that would allow the remote functionalization of aromatic systems. [ABSTRACT FROM AUTHOR] more...

A procedure for the [Cp*CoIII]-catalyzed direct C-H amidation of arenes with dioxazolone has been developed. This reaction proceeds under straightforward and mild conditions with a broad range of substrates, including anilides. A comparative study on the catalytic activity of Group 9 [{Cp*MCl2}2] complexes revealed the unique efficiency of the cobalt catalyst. [ABSTRACT FROM AUTHOR] more...

A versatile manganese(I) catalyst was employed in C-H aminocarbonylation reactions of heteroarenes with aryl as well as with alkyl isocyanates using a removable directing group approach. Detailed experimental mechanistic studies were suggestive of an organometallic C-H manganesation step, followed by a rate-determining migratory insertion. [ABSTRACT FROM AUTHOR] more...

Chiral cyclopentadienyl rhodium complexes promote highly enantioselective enol-directed C(sp²)-H functionalization and oxidative annulation with alkynes to give spiroindenes containing all-carbon quaternary stereocenters. High selectivity between two possible directing groups, as well as control of the direction of rotation in the isomerization of an O-bound rhodium enolate into the C-bound isomer, appear to be critical for high enantiomeric excesses. [ABSTRACT FROM AUTHOR] more...

Two mesoporous fluorinated metal-organic frameworks (MOFs) were synthesized from extensively fluorinated tritopic carboxylate- and tetrazolate-based ligands. The tetrazolate-based framework MOFF-5 has an accessible surface area of 2445 m²g-1, the highest among fluorinated MOFs. Crystals of MOFF-5 adsorb hydrocarbons, fluorocarbons, and chlorofluorocarbons (CFCs)--the latter two being ozone-depleting substances and potent greenhouse species--with weight capacities of up to 225%. The material exhibits an apparent preference for the adsorption of non-spherical molecules, binding unusually low amounts of both tetrafluoromethane and sulfur hexafluoride. [ABSTRACT FROM AUTHOR] more...

The reactivity towards AlMe3 of discrete cationic ansa-zirconocenes 2 a,b that are ubiquitously used in isoselective propylene polymerization and based on [{Ph(H)C(3,6-tBu2-Flu)(3- tBu-5-Et-Cp)}ZrMe2)] {Cp-Flu} and rac-[{Me2Si-(2-Me-4-Ph-Ind)2}ZrMe2] {SBI} was scrutinized. The first example of a structurally characterized Group 4 metallocene AlMe3 adduct (3b) is reported. In the presence of excess AlMe3, the {SBI}-based AlMe3 adduct 3b undergoes a slow decomposition via C–H activation in a bridging methyl unit to yield a new species (4b) with a trimetallic {Zr(μ-CH2)(μ-Me)AlMe(μ-Me)AlMe2} core. EXSY NMR data for the process 2b⇄3b→4b suggest very rapid and reversible binding of an additional AlMe3 molecule onto AlMe3 adduct 3b. The resulting heterotrimetallic species intermediates exchange of methyl groups between different metal centers and slowly undergoes the C–H activation reaction towards 4b. [ABSTRACT FROM AUTHOR] more...

The reactivity towards AlMe3 of discrete cationic ansa-zirconocenes 2 a,b that are ubiquitously used in isoselective propylene polymerization and based on [{Ph(H)C(3,6-tBuscript>2-Flu)(3- tBu-5-Et-Cp)}ZrMe2)] {Cp-Flu} and rac-[{Me2Si-(2-Me-4-Ph-Ind)2}ZrMe2] {SBI} was scrutinized. The first example of a structurally characterized Group 4 metallocene AlMe3 adduct (3b) is reported. In the presence of excess AlMe3, the {SBI}-based AlMe3 adduct 3b undergoes a slow decomposition via C–H activation in a bridging methyl unit to yield a new species (4b) with a trimetallic {Zr(μ-CH2)(μ-Me)AlMe(μ-Me)AlMe2} core. EXSY NMR data for the process 2b⇄3b→4b suggest very rapid and reversible binding of an additional AlMe3 molecule onto AlMe3 adduct 3b. The resulting heterotrimetallic species intermediates exchange of methyl groups between different metal centers and slowly undergoes the C–H activation reaction towards 4b. [ABSTRACT FROM AUTHOR] more...

A new mode of activation of an imine via a rare aza-substituted π-allyl complex is described. Palladium-catalyzed C(sp³)-H activation of the N-allyl imine and the subsequent nucleophilic attack by the α-alkyl cyanoester produced the 1-aza-1,3-diene as the sole regioisomer. In contrast, nucleophilic attack by the α-aryl cyanoester exclusively delivered the 2-aza-1,3-diene, which was employed in an inverse-electron-demand Diels-Alder reaction for heterobiaryl synthesis. [ABSTRACT FROM AUTHOR] more...

A new tandem C-N and C-C bond-forming reaction has been achieved through RhII/Pd0 catalysis. The sequence first involves an iodine(III) oxidant, then the in situ generated iodine(I) by-product is used as a coupling partner. The overall process demonstrates the synthetic value of iodoarenes produced in trivalent iodine reagent mediated oxidations. [ABSTRACT FROM AUTHOR] more...

2,2'-Diaryl acids are key building blocks for some of the most important and high-performance polymers such as polyesters and polyamides (imides), as well as structural motifs of MOFs (metal-organic frameworks) and biological compounds. In this study, a direct, regiospecific and practical dimerization of simple aromatic acids to generate 2,2'-diaryl acids has been discovered, which proceeds through two rhodium-catalyzed C¢H activations in water. This reaction can be easily scaled up to gram level by using only 0.4-0.6 mol% of the rhodium catalyst. As a proof-of-concept, the natural product ellagic acid was synthesized in two steps by this method. [ABSTRACT FROM AUTHOR] more...

The alkylation of complexes 2 and 7 with Grignard reagents containing β-hydrogen atoms is a process of considerable relevance for the understanding of C-H activation as well as C-C bond formation mediated by low-valent iron species. Specifically, reaction of 2 with EtMgBr under an ethylene atmosphere affords the bis-ethylene complex 1 which is an active precatalyst for prototype [2+2+2] cycloaddition reactions and a valuable probe for mechanistic studies. This aspect is illustrated by its conversion into the bis-alkyne complex 6 as an unprecedented representation of a cycloaddition catalyst loaded with two substrates molecules. On the other hand, alkylation of 2 with 1 equivalent of cyclohexylmagnesium bromide furnished the unique iron alkyl species 11 with a 14-electron count, which has no less than four β-H atoms but is nevertheless stable at low temperature against β-hydride elimination. In contrast, the exhaustive alkylation of 1 with cyclohexylmagnesium bromide triggers two consecutive C-H activation reactions mediated by a single iron center. The resulting complex has a diene dihydride character in solution ( 15), whereas its structure in the solid state is more consistent with an η3-allyl iron hydride rendition featuring an additional agostic interaction ( 14). Finally, the preparation of the cyclopentadienyl iron complex 25 illustrates how an iron-mediated C-H activation cascade can be coaxed to induce a stereoselective CC bond formation. The structures of all relevant new iron complexes in the solid state are presented. [ABSTRACT FROM AUTHOR] more...

Activation of aromatic CH bonds by a transition metal catalyst has received significant attention in the synthetic chemistry community. In recent years, rapid and site-selective extension of π-electron systems by C-H activation has emerged as an ideal methodology for preparing organic materials with extended π-systems. This Review focuses on recently reported π-extending C-H activation reactions directed toward new optoelectronic conjugated materials. [ABSTRACT FROM AUTHOR] more...

A catalytic asymmetric total synthesis of the potent and selective antileukemic Δ12-prostaglandin J3 (Δ12-PGJ3) is described. The convergent synthesis proceeded through intermediates 2 and 3, formed enantioselectively from readily available starting materials and coupled through an aldol reaction followed by dehydration to afford stereoselectively the cyclopentenone alkylidene structural motif of the molecule. [ABSTRACT FROM AUTHOR] more...

The direct ortho-trifluoromethylation of arenes, including heteroarenes, with TMSCF3 has been accomplished by a copper(II)-promoted C-H activation reaction which completes within 30 minutes. Mechanistic investigations are consistent with the involvement of C-H activation, rather than a simple electrophilic aromatic substitution (SEAr), as the key step. [ABSTRACT FROM AUTHOR] more...

Direct partial oxidation of methane, ethane, and propane to their respective trifluoroacetate esters is achieved by a homogeneous hypervalent iodine(III) complex in non-superacidic (trifluoroacetic acid) solvent. The reaction is highly selective for ester formation (>99%). In the case of ethane, greater than 0.5M EtTFA can be achieved. Preliminary kinetic analysis and density functional calculations support a nonradical electrophilic CH activation and iodine alkyl functionalization mechanism. [ABSTRACT FROM AUTHOR] more...

Formation of C-C bonds from CO2 is a much sought after reaction in organic synthesis. To date, other than C-H carboxylations using stoichiometric amounts of metals, base, or organometallic reagents, little is known about C-C bond formation. In fact, to the best of our knowledge no catalytic methylation of C-H bonds using CO2 and H2 has been reported. Described herein is the combination of CO2 and H2 for efficient methylation of carbon nucleophiles such as indoles, pyrroles, and electron-rich arenes. Comparison experiments which employ paraformaldehyde show similar reactivity for the CO2/H2 system. [ABSTRACT FROM AUTHOR] more...

A novel and facile C-H bond fluorination proceeds under remarkably mild conditions (close to room temperature in most cases). Both aromatic and olefinic C(sp²)-H bonds with a wide range of electronic properties are selectively fluorinated in the presence of a catalytic amount of simple, cheap, and nontoxic nitrate as the promoter. A PdII/PdIV catalytic cycle that is initiated by an in situ generated cationic [Pd(NO3)]+ species was proposed based on preliminary mechanistic studies. [ABSTRACT FROM AUTHOR] more...

Formation of C-C bonds from CO2 is a much sought after reaction in organic synthesis. To date, other than C-H carboxylations using stoichiometric amounts of metals, base, or organometallic reagents, little is known about C-C bond formation. In fact, to the best of our knowledge no catalytic methylation of C-H bonds using CO2 and H2 has been reported. Described herein is the combination of CO2 and H2 for efficient methylation of carbon nucleophiles such as indoles, pyrroles, and electron-rich arenes. Comparison experiments which employ paraformaldehyde show similar reactivity for the CO2/H2 system. [ABSTRACT FROM AUTHOR] more...