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.     

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.     

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.     

Functionalized pyrroles from vinylaziridines and alkynes via rhodium-catalyzed domino ring-opening cyclization followed by CC bond migration

Rhodium(I)-catalyzed intermolecular cycloadditions of alkynes with vinyl aziridines bearing a conjugated carbonyl group in the olefin moiety followed by the double migration resulted in the formation of pyrrole derivatives in a one pot fashion.     

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.     

Visible-light-induced photocatalytic difluoroalkylation of 3-substituted benzo[d]isoxazoles via direct and regioselective CH functionalization

The difluoroalkylation of unactivated benzo[d]isoxazoles with ethyl difluorobromoacetate by visible-light photoredox catalysis via direct and regioselective CH functionalization has been efficiently achieved under mild reaction conditions. The difluoroalkylated adducts could be readily converted to a variety of corresponding CF₂-containing heterocycles, demonstrating the synthetic utility of the present approach.     

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.     

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.     

Phase relations and exsolution phenomena in the system NiOTiO2

The phase relations in the system NiOTiO₂ were studied between 1000 and 1600°C using quenched powder specimens, DTA runs, and single crystal diffusion couples. Quenching experiments establish the stable phases TiO₂ (rutile), NiTiO₃ an ilmenite structure type, Ni_2(1+x)Ti_1?xO₄ (x ≥ 0.16), a cation-excess spinel, and Ni_1?2xTi_xO (rocksalt structure type). DTA runs reveal the existence of an additional nonstoichiometric ilmenite phase Ni_1?2xTi_1+xO₃ (x ≤ 0.03) above 1260°C. In quenched (1500, 1450°C) or slowly cooled single crystal diffusion couples, mutual oriented exsolutions occur in the rutile crystal and in the ilmenite diffusion zone. Orientation relations are: {101}_rutile{1120}_ilmenite; ∥010〉_rutile∥00.1〉_ilmenite. The cation-excess spinel decomposes below 1375°C into oriented intergrowth of NiTiO₃ (ilmenite) and NiO: {111}_NiO{0001}_NiTiO3; ∥110〉_NiO∥21.0〉_NiTiO3.     

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.     

The Crystal and Molecular Structure of Bis(cyclopentadienyldicarbonylchromium) (CrCr)

The crystal structure of bis(cyclopentadienyldicarbonyl-chromium) has been determined by x-ray diffraction. The compound crystalizes in the triclinic system, space group P1¯(C¹_i, No. 2) with unit cell parameters: a, 7.829(3); b, 14.543(6); c, 6.588(2)Å; α, 94.67(3), β, 110.70(3); γ, 104.04°(3); V, 699.1(4)ų; z=2. There are two independent molecules per unit cell located at the inversion centers at O,O,O and O, 1/2, O. The CrCr bond distances are, respectively 2.200(3) and 2.230(3), thus supporting their formulation as triple bonds. The CpCrCr angles in the two molecules are 165.0° and 158.7°, respectively. The structural features are compared with those of Cp₂Mo₂(CO)₄, which has a linear CpMoMoCp axis; and the differences rationalized in terms of electronic interactions of the Cp-ligand with the orbitals of the M₂ unit. The differences observed in the structures of the two independent molecules are also related to the proposed bonding model and to packing considerations.     

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.     

Reactions of TIN(II) halides with compounds containing a transition metalcarbon σ-bond

Tin(II) chloride inserts into the ironcarbon σ-bond in MeFe(CO)₂Cp (Cp = cyclopentadienyl), in refluxing methanol or THF, to give MeClSnFe(CO)₂- Cp and traces of Cl₃SnFe(CO)₂Cp, but, with EtFe(CO)₂Cp, a mixture of the insertion product, Cl₃SnFe(CO)₂Cp, and Cl₂Sn[Fe(CO)₂Cp]₂ is formed. Insertion of tin(II) chloride was not observed for MeMo(CO)₃Cp and MeMn(CO)₅; in these reactions, and in those between tin(II)_bromide and MeFe(CO)₂Cp, EtFe(CO)₂Cp and Memo(CO)₃Cp, mixtures of halo—metal carbonyls and halotin—metal carbonyls result.     

One-pot synthesis of N-fused 1,2,4-triazoles and related heterocycles via I2/TBHP-mediated oxidative CN bond formation

A metal-free iodine/TBHP-mediated oxidative CN bond formation for the one-pot synthesis of N-fused 1,2,4-triazoles and related heterocycles via cyclization has been developed. This reaction which is amenable to scale-up affords the corresponding products with good to excellent yields and tolerates a wide range of functional groups.     

Action des composes dicarbonyles-1,2 sur des composes du phosphore dicoordonne a liaison pn et sur leurs oligomeres.

Triazaphospholes react with 1,2-diketones to give spirocyclic phosphorus compounds by a 1.1 addition at phosphorus atom; with o-quinones one obtains spirobicyclic hexacoordinated phosphorus compounds. The reaction of 1,2-diketones with λ³-phosphazene oligomers appears different, to some extent, and can be used as a test for the existence of a monomer-oligomer equilibrium.     

Reactions of M(CO)6 (M Cr,Mo) with formamidines

The reactions of hexacarbonyl-molybdenum and -chromium with arylformamidines yield Mo₂{HC(NR)₂}₄ and Cr₂{HC(NR)₂}₄, respectively. In the case of Mo the reaction proceeds by the formation of pentacarbonyl formamidinemolybdenum and tetracarbonyldiformamidinemolybdenum complexes. Reaction of Mo₂{HC(NR)₂}₄ with Mo(CO)₆ yield the novel complexes Mo₂{HC(NR)₂}₃-{HC(NR)NR · Mo(CO)₃} and Mo₂{HC(NR)₂}₂ {HC(NR)NR · Mo(CO)₃}₂, in which the [Mo(CO)₃] moiety is bonded to one of the aromatic groups. In the case of chromium, only Cr₂{HC(NR)₂}₃ {HC(NR)NR · Cr(CO)₃¦ could be prepared. In solution, the formamidine complexes show monomer—dimer equilibria, which are strongly dependent on the nature of R. W(CO)₆ reacts with formamidines, but did not yield complexes analogous to those for chromium and molybdenum. The properties of the new complexes are discussed.     

Stereoselective synthesis of the C14C23 fragment of biselyngbyolide A and B enabled by transition metal catalysis

Transition metal catalysis has enabled the highly stereoselective and protecting group-free synthesis of the C14C23 fragment of the apoptosis-inducing natural products biselyngbyolide A and B. A Pd-catalyzed Stille reaction between a vinyl stannane and a crotyl carbonate formed the skipped diene with complete control of the trisubstituted bond and excellent control over the branched/linear products. A Cu-catalyzed Stahl oxidation was used to form the requisite aldehyde needed for a Ag-catalyzed asymmetric allylation. The latter provided the final fragment with excellent stereochemical control.