Iron-catalyzed cross-dehydrogenative CN coupling of thiohydantoins with various amines

A novel iron-catalyzed CN bond construction method for the hetero-cross-dehydrogenative coupling (CDC) of diverse thiohydantoins with amines utilizing TBHP as the oxidant was developed. This sp³ CH amination at the carbons alpha to carbonyl groups of thiohydantoin tolerates the presence of a wide range of functional groups and provides the corresponding N-substituted amines in moderate to good yields. Various substrate scopes and optimum reaction conditions leads inside in organic synthesis.     

Total synthesis of lithospermic acid using Fe-catalyzed Cross-Dehydrogenative-Coupling reaction and Pd-catalyzed ester-directed CH olefination

The total synthesis of lithospermic acid has been accomplished employing two CH activation reactions as key steps. Fe-catalyzed Cross-Dehydrogenative-Coupling reaction was used for the rapid construction of benzofuran framework. Pd-catalyzed ester-directed CH olefination allowed the efficient assembly of the dihydrobenzofuran ester and acrylate moieties.     

Propargylic CH activation using a Cu(II) 2-quinoxalinol salen catalyst and tert-butyl hydroperoxide

The oxidation of alkynes to α,β-acetylenic carbonyls was achieved using only 1?mol% of a Cu(II) 2-quinoxalinol salen catalyst with tert-butyl hydroperoxide. These reactions proceed under mild conditions (70?°C) with excellent selectivity, producing yields up to 78%, and were used on a variety of alkyne substrates to produce the desired corresponding α,β-acetylenic ketones. In addition, these reactions can be run under aqueous conditions using a sulfonated version of the 2-quinoxalinol salen with good yields, reducing the need for volatile organic solvents.     

Site selective [bmIm]OH catalyzed CC bond functionalization under green conditions

Effective methodology that activates selectively either end of a carbon–carbon triple bond requires key challenge of differentiating between the multitude of CC bonds present in complex organic molecule. The synthetic strategy exploited the electronic biases within the substrate and successfully achieved site–selective [bmIm]OH catalyzed CC bond functionalization under mild reaction conditions. This resulted in C-2-selective addition of phenacyl bromide on p-substituted phenyl acetylene and C-1 selective addition on the o-substituted phenyl acetylene leading to CC bond formation. The reaction proceeded smoothly with excellent yield under ambient conditions. This report demonstrates the progress on the catalytic activity of recyclable [bmIm]OH for selective CC bond formation.     

The investigation on the NH reactivity of pentacoordinate spirophosphoranes by H/D exchange and NMR experiments

Different pentacoordinate spirophosphoranes were investigated by H/D exchange and NMR tracking experiments. The H/D exchanged site of spirophosphoranes was confirmed to be the NH bond instead of the PH bond according to the integration of the signal changes in proton-decoupled, proton-coupled ³¹P NMR and ¹H NMR tracking experiments. The reactivity of NH bond at the spiroring of spirophosphoranes was explored by the rate constant of H/D exchange of different spirophosphoranes. The results demonstrated that the reactivity of NH bond of spirophosphoranes was influenced by steric hindrance and the species of substituent at phosphorus atom, and the electronic effect of the substituent was the main effect factor on the reactivity of the NH bond. The strong electron-withdrawing group at phosphorus resulted in more reactive NH bond of spirophosphoranes. These results are beneficial to further understand and explore the characteristics of pentacoordinate spirophosphoranes.     

Regioselective remote CH fluoroalkylselenolation of 8-aminoquinolines

Herein, the direct C-5 fluoroalkylselenolation of 8-aminoquinolines is described. The Pd-catalyzed reaction is performed with the in situ generated fluoroalkylselenyl chloride and various 8-aminoquinoline amides or sulfonamides. The desired products were formed in moderate to excellent yields.     

Ruthenium-catalyzed nitrogen-directed ortho CH borylation of aromatic imines with pinacolborane

An efficient ruthenium catalyst system for the direct ortho CH borylation of aromatic imines is described. The reaction of tert-butyl-1-arylmethanimines with pinacolborane in the presence of Ru(cod)(cot), followed by hydrolysis, to afford the ortho-formyl-substituted arylboronates. The borylation was achieved with complete mono-selectivity.     

Facile CH arylation using catalytically active terminal sulfurs of 2 dimensional molybdenum disulfide

The first methodology of CH arylation of heteroarene via 2D transition metal dichalcogenides that have catalytically active edge functional groups was described. The terminal sulfur groups could effectively catalyze a formation of an azo-linked intermediate with aryl diazonium salts, leading to produce heteroarenes with good yields. This novel methodology using bulk 2D transition metal dichalcogenides that have catalytically active edge functional groups can apply for various reactions to achieve CC bond formation in the fields of heterogeneous catalysis that is easily separable, highly reusable, and inexpensive method.     

Rhodium-catalyzed CH activation/cyclization of enaminones with sulfoxonium ylides toward polysubstituted naphthalenes

A rhodium-catalyzed ortho-CH functionalization and annulation between enaminones and sulfoxonium ylides was developed, affording a series of multi-substituted naphthalenes in good to moderate yields with excellent functional group compatibility. The procedure featured with enaminone acting as both a directing and cyclization bifunctional group, and the application of sulfoxonium ylide in CH functionalization.     

Phosphinate selective hosts and importance of CH hydrogen bonding for affinity modulation toward anion guests

Even though phosphinate and its analogs are very important guests in nature, the artificial receptors which are capable of selective recognition of phosphinate are rare. Here, we report a series of acetate and phosphinate selective hosts (1, 2 and 3) which utilize amide NH and aliphatic CH groups as hydrogen bonding donors. In this series of receptors, even though the amide NH hydrogen bonding element was found to be the most significant, by varying the polarity of CH group, the magnitude of recognition could be modulated considerably. The affinities of host 3 against all the tested anion guests showed significantly higher affinities compared with those of hosts 1 and 2, and this could be attributed to the difference of CH group polarities among the receptors 1, 2 and 3. C_α-H hydrogen in host 3 is the most highly polarized by the charged pyridinium group. Therefore, it is the strongest host in this series of hosts. From the experiments shown here, we demonstrated the importance of CH hydrogen bonding element as a decisive modulating moiety for anionic recognition.     

Synthesis of functionalized benzothiadiazine 1,1-dioxide derivatives via intramolecular CH activation reactions of trichloroacetamidine and benzenesulfonyl chloride

The synthesis of functionalized benzothiadiazine 1,1-dioxide derivatives was achieved through a novel three-component intramolecular CH activation reaction of trichloroacetonitrile, benzenesulfonyl chloride, and various primary amines. This reaction was performed in the presence of catalytic copper(I) and l-proline as the ligand in tetrahydrofuran at room temperature.     

Base-promoted nucleophilic fluoroarenes substitution of CF bonds

With the use of KOH/DMSO as the superbase medium, the nucleophilic fluoroarene substitution for CF bonds is presented. The transformation proceeds smoothly with the use of fluoroarenes bearing not only electron-withdrawing group, but also electron-donating group and a variety of nucleophiles such as alcohols, phenols, amines, amides and nitrogen-heterocyclic compounds. The double nucleophilic substitution using ortho-difluoroarenes and nucleophiles bearing ortho-dinucleophilic groups results in the formation of 2,3-dihydro-1,4-benzodioxins, dibenzo[b,e][1,4]dioxins and 10H-phenoxazines in moderate to good yields.     

Rhodium-catalyzed NH-indole-directed ortho CH coupling of 2-arylindoles with diazo compounds via metal carbene migratory insertion

A high regioselective rhodium-catalyzed ortho CH coupling of 2-arylindoles with diazo compounds via NH-indole-directed CH bond activation has been developed. The catalytic reaction features mild reaction conditions, broad substrate scope and good functional group tolerability.     

Ligation state of nickel during CO bond activation with monodentate phosphines

The oxidative addition of phenolic electrophiles at Ni(0) in the presence of monodentate phosphine ligands was studied with both dispersion-free and dispersion-containing DFT methods. With the popular bulky ligand PCy₃, consideration of dispersion has a striking effect on the predicted ligation state of nickel during oxidative addition of aryl sulfamates. Dispersion-containing methods such as M06L indicate a clear preference for a bis-phosphine ligated transition state (TS), while dispersion free methods like B3LYP strongly favor a mono-phosphine ligated TS. This discrepancy in predicted ligation state is also found with small phosphines (PMe₃) in combination with some aryl electrophiles (carbamates, acetates, pivalates, chlorides), but a bis-PMe₃-ligated TS is predicted regardless of dispersion for other electrophiles (sulfamates, mesylates, tosylates). DFT calculations that include dispersion also offer a possible explanation for the observed poor efficacy of P^tBu₃ as a ligand in Ni-catalyzed cross-coupling reactions.     

One-pot Sonogashira coupling,hydroamination of alkyne and intramolecular CH arylation reactions toward the synthesis of indole-fused benzosultams

A one-pot Sonogashira coupling, hydroamination of alkyne and CH arylation reactions for the synthesis of indole-fused benzosultams are described. This method allows access to a variety of indole-fused seven membered benzosultams in good to excellent yields. The free indolyl nitrogen containing indole-fused benzosultams are also prepared by this method. The structures of the synthesized compounds are confirmed by single crystal XRD studies.     

Interstitial superstructures in the TaD system

Ordered deuterium arrangements and order-disorder transformations of the tantalum deuterides in the range TaD_0.50TaD_0.78 have been studied by neutron diffraction and calorimetry at temperatures between ?170 and 120°C. In addition to the disordered phase (α), three ordered phases based on the superstructures Ta₂D_1+x (β₁), Ta₄D₃, (γ), and TaD (δ) are clarified. The Ta₂D_1+x structure is a nonstoichiometric from of the Ta₂D superstructure over the rangex < 0.5. The γ-phase is formed below ?70°C near Ta₄D₃, and transforms into theβ₁and δ-phases, respectively, in the hypo and hyperstoichiometric compositions. The δ-phase that exists beyond TaD_0.75 changes to the disordered α-phase around 100°C.     

Synthesis of triphenylene derivatives by Pd-catalyzed Suzuki coupling/intramolecular CH activation between arylboronic acids and dibromobiphenyls

An efficient and regioselective synthesis of functionalized triphenylenes via palladium-catalyzed Suzuki-Miyaura coupling and subsequent intramolecular CH activation between arylboronic acids and dibromobiphenyls was developed. This methodology showed excellent atomic economy and regiospecificity as well as synthetic feasibility of unsymmetrical triphenylenes.     

Designing chiral amido-oxazolines as new chelating ligands devoted to direct Cu-catalyzed oxidation of allylic CH bonds in cyclic olefins

A new type of amido-oxazoline ligands was conveniently synthesized from inexpensive and commercially available materials in high yields and enantiomeric excesses. The corresponding chiral copper complexes with this class of ligands [C₂ symmetric S,S-bis(amido-oxazoline-Cu(II) complex] were synthesized accordingly. The ORTEP diagram of ligand 6a and complex 6a-copper were compared and characterization of the complex confirmed the involvement of both dentate parts of the ligands, the oxygen and nitrogen atoms, in complexation with copper. The utilization of this amido-oxazoline ligands in the copper-catalyzed enantioselective esterification of allylic CH bonds of cyclic olefins with tert-butyl-4-nitrobenzoperoxoate resulted in the highest activities, yields (up to 95%) and enantioselectivities (up to 96%) in the presence of HZSM-5 zeolite. These new findings highlight the protocol as one of the most attractive and useful methods for the oxidation of the asymmetric allylic CH bond of cycloalkenes compared to other methodologies reported in the literature.     

Palladium-catalyzed phosphination and amination through CH bond functionalization on biphenyl: Amido-substituent as directing group

The formation of N-(2'-(diphenylphosphoryl)-[1,1′-biphenyl]-2-yl)-2,3,4,5,6-pentafluorobenzamide (3_eaaa) has been achieved through the palladium-catalyzed and Ag(I)-assisted CH functionalization of N-([1,1′-biphenyl]-2-yl)-2,3,4,5,6-pentafluorobenzamide (1_eaa) via phosphination and in the presence of diphenylphosphine oxide (2_a). The reaction was accompanied with small amount of carbazole derivative, (9H-carbazol-9-yl)(perfluorophenyl)methanone (4_eaa). Crystal structures of 3_eaaa and 4_eaa were both determined by X-ray crystal diffraction methods. Indeed, phosphination took place at the ortho-position of inter-annular ring of 1_eaa. Substituents with various electron-withdrawing/donating capacities on the amido-fragment of 1 were found to greatly affect the ratio distribution of products 3 and 4. By contrast, substituents on various locations of the biphenyl in 1 do not influence much on the outcome of the products distribution. A reaction mechanism is proposed to account for these experimental observations. Computational studies employing Density Functional Theory methods (DFT) on this proposed mechanism found that the electron density property of the palladium metal center in the intermediate II is critical to the formation of either 3 or 4. A relatively electron-poor palladium metal center favors the pathway of forming 3. On the contrary, the pathway of producing 4 will be prevailed while the palladium metal center is having fair amount of electron-density in the proposed intermediate II.     

Rh(III)-catalyzed, 1,2,3-triazole-assisted directed CH coupling with diazo diphosphonates

A mild and efficient procedure was developed for the [Cp1Rh(III)]-catalyzed, 1,2,3-triazole directed CH coupling with diazomethylene-diphosphonates. This protocol provided a step- and atom-economical protocol for CC bond formation and led to structurally diverse 2-(1,2,3-triazol-2-yl)benzyl diphosphonates in good to excellent yields.