Reactions of Tertiary Alcohols with Palladium(II) Tetraaqua Complex. Formation of Palladium π-Allyl Complexes

Transformations of 2-methyl-2-propanol, 2-methyl-2-butanol, 2-methyl-2-pentanol, 1-methyl-1-cyclohexanol, and 1-ethyl-1-cyclohexanol in the presence of tetraaquapalladium(II) ions in perchloric acid madium were studied. It was found that the reactions give rise to palladium(II) -allyl complexes. The reaction rate increases and the yield of the corresponding -allyl complex decreases with increasing hydrocarbon chain length. Addition of iron(III) ions to the systems essentially increases the yield of palladium -allyl complexes. The olefin formed from the corresponding tertiary alcohol participates in the formation of the palladium -allyl complex. Oxidation of 2-methyl-2-butanol with tetraaquapalladium(II) ions gives the isomeric palladium -allyl complexes [Pd(³-(CH₃)₂CCHCH₂)bpy]ClO₄ and [Pd(³-(CH₂C(CH₃)CHCH₃))bpy]ClO₄, which were isolated using 2,2'-bipyridyl and characterized by ¹H and ¹³C NMR spectroscopy.     

Cyclometalated Ruthenium Pincer Complexes as Catalysts for the α-Alkylation of Ketones with Alcohols

Ruthenium PNP pincer complexes bearing supplementary cyclometalated C,N-bound ligands have been prepared and fully characterized for the first time. By replacing CO and H⁻ as ancillary ligands in such complexes, additional electronic and steric modifications of this topical class of catalysts are possible. The advantages of the new catalysts are demonstrated in the general α-alkylation of ketones with alcohols following a hydrogen autotransfer protocol. Herein, various aliphatic and benzylic alcohols were applied as green alkylating agents for ketones bearing aromatic, heteroaromatic or aliphatic substituents as well as cyclic ones. Mechanistic investigations revealed that during catalysis, Ru carboxylate complexes are predominantly formed whereas neither the PNP nor the CN ligand are released from the catalyst in significant amounts.     

Reactions of Polyfluorinated Telomeric Alcohols with ε-Caprolactam

The possibility of preparing fluorinated oligomeric derivatives of -aminocaproic acid by reaction of polyfluorinated telomeric alcohols H(CF₂CF₂) _n CH₂OH (n = 1-4) with -caprolactam under conditions of homogeneous catalysis (triethylamine, dimethylformamide) was examined. The thermal stability of the oligomers was studied in relation to the fluorine content.     

Reactions of α-halonitrosoalkanes with resorcinol

-Halonitrosoalkanes react with resorcinol as nitrosylating agents to form 3-hydroxy-N-(2,4-dihydroxyphenyl)-1,4-quinone imine.Translated fromIzvestiya Akademioi Nauk. Seriya Khimicheskaya, No. 3, pp.773–774, March, 1996.     

Reactions of α-nitroacrylates with thiophenols

Reactions of α-nitroacrylates with aromatic thiols like 4-methyl- and 4-chlorothiophenols afford a series of new 3-arylsulfanyl-2-nitropropanoates. The latter were isolated as diastereomerically pure substances or mixtures of two diastereomers. Structures of the obtained S-adducts were confirmed by IR, ¹H and ¹³C-{¹H} NMR spectroscopy using HMQC and HMBC experiments.     

Copper/Ruthenium Relay Catalysis for Stereodivergent Access to δ-Hydroxy α-Amino Acids and Small Peptides

An atom- and step-economical and redox-neutral cascade reaction enabled by asymmetric bimetallic relay catalysis by merging a ruthenium-catalyzed asymmetric borrowing-hydrogen reaction with copper-catalyzed asymmetric Michael addition has been realized. A variety of highly functionalized 2-amino-5-hydroxyvaleric acid esters or peptides bearing 1,4-non-adjacent stereogenic centers have been prepared in high yields with excellent enantio- and diastereoselectivity. Judicious selection and rational modification of the Ru catalysts with careful tuning of the reaction conditions played a pivotal role in stereoselectivity control as well as attenuating undesired α-epimerization, thus enabling a full complement of all four stereoisomers that were otherwise inaccessible in previous work. Concise asymmetric stereodivergent synthesis of the key intermediates for biologically important chiral molecules further showcases the synthetic utility of this methodology.     

Reactions of Chelates with Macrocyclic Ligands. Complexation between Tetraphenylporphine and Cu(II) Complexes with α-Amino Acids

The reactions of tetraphenylporphine (H₂TPP) with copper(II) chelates in DMSO were studied. -Amino acids (glycine, -alanine, valine, leucine, tyrosine, and glutamine) were used as chelating ligands. The study of the reaction kinetics showed that Cu(II) chelates with alanine and the other amino acids are less reactive in these reactions than acetylacetonates, -nitroso--naphtholates, and hydroxyquinolates. The exception is a Cu(II) complex with tyrosine. The relationship between the structure of the above chelates and the rate of their reactions with porphyrin was determined.     

Reactions of α-aminoazoles with diethyl benzylidenemalonate

Cyclocondensations of diethyl benzylidenemalonate with 3-amino-5-methylpyrazole, 3,5-diamino-1,2,4-triazole, 3,4,5-triamino-1,2,4-triazole, and 2-amino-benzimidazole in alcohols take a single route and lead to the formation of functionally substituted partially hydrogenated pyrazolo-, triazolo[1,5-a]-pyrimidin-5-ones and pyrimido[1,2-a]benzimidazol-2-one respectively. From reaction mixtures involving 3-amino-1,2,4-triazole and its 5-methylsulfanyl analog in methanol the intermediate products of heterocyclization were isolated forming as a result of alkylation with the β-carbon of the unsaturated ester the endocyclic nucleophilic sites of aminoazoles. The structure of one among the products obtained, diethyl(3-amino-5-methylsulfanyl-1,2,4-triazol-2-yl)benzylmalonate was proved by X-ray crystallography. In DMF the same reagents yielded mixtures of partially hydrogenated triazolo[1,5-a]pyrimidin-5-ones.     

Cu/Pd Synergistic Dual Catalysis: Asymmetric α-Allylation of an α-CF3 Amide

Despite the burgeoning demand for fluorine-containing chemical entities, the construction of CF₃-containing stereogenic centers has remained elusive. Herein, we report the strategic merger of Cu^I/base-catalyzed enolization of an α-CF₃ amide and Pd⁰-catalyzed allylic alkylation in an enantioselective manner to deliver chiral building blocks bearing a stereogenic carbon center connected to a CF₃, an amide carbonyl, and a manipulable allylic group. The phosphine complexes of Cu^I and Pd⁰ engage in distinct catalytic roles without ligand scrambling to render the dual catalysis operative to achieve asymmetric α-allylation of the amide. The stereoselective cyclization of the obtained α-CF₃-γ,δ-unsaturated amides to give tetrahydropyran and γ-lactone-fused cyclopropane skeletons highlights the synthetic utility of the present catalytic method as a new entry to non-racemic CF₃-containing compounds.     

Green-Light Activation of Push–Pull Ruthenium(II) Complexes

Synthesis, characterization, electrochemistry, and photophysics of homo- and heteroleptic ruthenium(II) complexes [Ru(cpmp)₂]²⁺ ( 2²⁺ ) and [Ru(cpmp)(ddpd)]²⁺ ( 3²⁺ ) bearing the tridentate ligands 6,2’’-carboxypyridyl-2,2’-methylamine-pyridyl-pyridine (cpmp) and N,N’-dimethyl-N,N’-dipyridin-2-ylpyridine-2,6-diamine (ddpd) are reported. The complexes possess one ( 3²⁺ ) or two ( 2²⁺ ) electron-deficient dipyridyl ketone fragments as electron-accepting sites enabling intraligand charge transfer (ILCT), ligand-to-ligand charge transfer (LL'CT) and low-energy metal-to-ligand charge transfer (MLCT) absorptions. The latter peak around 544 nm (green light). Complex 2²⁺ shows ³MLCT phosphorescence in the red to near-infrared spectral region at room temperature in deaerated acetonitrile solution with an emission quantum yield of 1.3 % and a ³MLCT lifetime of 477 ns, whereas 3²⁺ is much less luminescent. This different behavior is ascribed to the energy gap law and the shape of the parasitic excited ³MC state potential energy surface. This study highlights the importance of the excited-state energies and geometries for the actual excited-state dynamics. Aromatic and aliphatic amines reductively quench the excited state of 2²⁺ paving the way to photocatalytic applications using low-energy green light as exemplified with the green-light-sensitized thiol–ene click reaction.     

Stereodivergent Synthesis of Allenes with α,β-Adjacent Central Chiralities Empowered by Synergistic Pd/Cu Catalysis

The stereodivergent synthesis of allene compounds bearing α,β-adjacent central chiralities has been realized via the Pd/Cu-catalyzed dynamic kinetic asymmetric alkylation of racemic allenylic esters. The matched reactivity of bimetallic catalytic system enables the challenging reaction of racemic aryl-substituted allenylic acetates with sterically crowded aldimine esters smoothly under mild reaction conditions. Various chiral non-natural amino acids bearing a terminal allenyl group are easily synthesized in high yields and with excellent diastereo- and enantioselectivities (up to >20 : 1 dr, >99 % ee). Importantly, all four stereoisomers of the product can be readily accessed by switching the configurations of the two chiral metal catalysts. Furthermore, the easy interconversion between the uncommon η³-butadienyl palladium intermediate featuring a weak C=C/Pd coordination bond and a stable Csp²−Pd bond is beneficial for the dynamic kinetic asymmetric transformation process (DyKAT).     

Domino meta-C−H Ethyl Glycosylation by Ruthenium(II/III) Catalysis: Modular Assembly of meta-C-Alkyl Glycosides

Glycosyl anomeric radical addition reactions have been well-explored and proved efficient for the C-alkyl glycosides synthesis, but multicomponent Domino transformations for the rapid and controllable construction of structurally diversified C-alkyl glycosides in a single step are still rare. In contrast, we, herein, report a ruthenium(II)-catalyzed Domino meta-C−H ethyl glycosylation, enabling the construction of challenging meta-C-alkyl glycosides. Our ruthenium(II) catalysis was reflected by the mild reaction condition, exclusive meta-site selectivity and high levels of anomeric selectivity. In addition, the ruthenium(II)-catalyzed Domino meta-C−H glycosylation allowed for the synthesis of versatile 1,2-trans-C-alkyl glycosides with commercially available vinyl arenes, acrylates and easily accessible glycosyl bromides.     

Metal-ylide complexes—II[1]: Reactions of some pyridinium ylides with selected salts of cobalt(II), copper(II) and palladium(II)

Palladium(II)chloride affords simple coordination compounds withC₅H₅N⁺N^-COMe and C₅H₅N⁺N^-COEt but the derivative of N-(1-pyridinio)proprionamidate decomposes with evolution of HCl at the melting point.Both C₅H₅N⁺N^-SO₂Ph (L) and C₅H₅N⁺N^-COPh (L′) give coordination compounds with cobalt(II) and copper(II). The series [ML₄] (CLO₄)₂ (M = Co, Cu, Zn) is isomorphous and evidence is available from spectroscopic measurements (UV and ESR) to support the tetrahedral environment about the metal ions, although in the copper compound some distortion is present. [Co₂L₄X₂]X₂ (X = Cl, Br) and [Cu₂L₄Cl₂]Cl₂ are isomorphous, dimeric and have pseudo tetrahedral stereochemistry; [CuL₂Br₂] and [ZnL₂Cl₂ are isomorphous and tetrahedral. The spectroscopic data are discussed in such depth as the data derived from polycrystalline specimens permit. [CoL₄′] (ClO₄)₂ contains O-bonded C₅H₅N⁺N^-COPh and exists in at least two polymorphic forms one of which is magnetically abnormal [Co₂-L₄′Cl₂]Cl₂ is dimeric and contains both O- and N-bonded ylide, [Co₂L₂X₄] are also dimers but contain only the O-bonded ylide. [CuL_3·5′] (ClO₄)₂, which contains copper(II) in a distorted 6-coordinate environment, is contrasted with the well defined [CuL₄] (ClO₄)₂ (above). N-(1-pyridinio)benzamidate undergoes NN bond rupture to give pyridine and phenylisocyanate at 190–200°C, but this decomposition temperature may be lowered by approx. 100°C in the presence of anhydrous copper(II) chloride which is shown to give an N-bonded complex with the ylide.     

Reactions of Phosphorodiamidous Acid Esters with α-Halocarbonyl Compounds

Reactions of ethyl and tert-butyl phosphorodiamidites with chloroacetone, bromoacetone, and -chloroethyl acetate were studied. The reaction pathway is determined by the structure of the intermediate quasiphosphonium compound responsible for the formation of the Arbuzov product as well as for the occurrence of the amonalous reaction yielding vinyl phosphate.     

Reactions of Lithium Acylates α-Carbanions with 1,2-Diiodoethane

Russian Journal of General Chemistry - The interaction of lithium acylates α-carbanions (obtained via metallation of acetic, butyric, and isobutyric acids with lithium diisopropylamide) with...     

Complexes of copper(II) with sugar α-amino acids as ligands

Summary Complexes of Cu^II with 2-(benzylamino)-2-deoxy-d-glycero-d-talo heptonic acid (BnMa) and 2-(benzylamino)-2-deoxy-d-glycero-l-gluco heptonic acid (BnGa) were prepared and characterized by elemental analysis, thermal data, i.r., electronic and e.s.r. spectra, magnetic susceptibility measurements, and X-ray powder diffraction. The metal:ligand stoichiometry of these complexes is 12 and coordination around Cu^II seems to be octahedral, with the ligands bound through the N atom of the amino group and O atoms of the bridging carboxylate group.     

Polychloromethylation-Initiated Radical 1,2-Aryl Migration of α,α-Diarylallyl Alcohols via Visible-Light Photoredox Catalysis

A visible-light induced radical 1,2-aryl migration of α,α-diarylallyl alcohols was developed under mild and metal-free conditions. Commercially available CHCl₃ and CH₂Cl₂ were used as tri- and dichloromethyl radical precursors. Structurally diverse β-polochloromethylated ketones were obtained in good to moderate yields via neophyl-type rearrangement. Besides, the polychloromethyl group can be easily transformed into other useful functional groups.