Base-Selective Five- versus Six-Membered Ring Annulation in Palladium-Catalyzed C–C Coupling Cascade Reactions: New Access to Electron-Poor Polycyclic Aromatic Dicarboximides

Palladium-catalyzed base-selective annulation of dibromonaphthalimide to different aryl boronate esters by combined Suzuki–Miyaura cross-coupling and direct C−H arylation afforded a series of new five- and six-membered ring annulated electron-poor polycyclic aromatic hydrocarbons. Cesium carbonate (Cs₂CO₃) as auxiliary base in these C−C coupling cascade reactions led exclusively to six-membered ring annulation, while the use of organic base diazabicycloundecene (DBU) afforded the corresponding five-membered ring annulated products. This base-dependent selective mode of annulation is attributed to different mechanistic pathways directed by the applied base. The selective annulation was revealed by single crystal X-ray analysis of the respective five- and six-membered ring annulated products. The optical and redox properties of the new polycyclic aromatic dicarboximides were characterized by UV/Vis absorption and fluorescence spectroscopy and cyclic voltammetry.     

Rhodium-Catalyzed Alkylation of C−H Bonds in Aromatic Amides with Non-activated 1-Alkenes: The Possible Generation of Carbene Intermediates from Alkenes

The alkylation of C−H bonds (hydroarylation) in aromatic amides with non-activated 1-alkenes using a rhodium catalyst and assisted by an 8-aminoquinoline directing group is reported. The addition of a carboxylic acid is crucial for the success of this reaction. The results of deuterium-labeling experiments indicate that one of deuterium atoms in the alkene is missing, suggesting that the reaction does not proceed through the commonly accepted mechanism for C−H alkylation reactions. Instead the reaction is proposed to proceed through a carbene mechanism. The carbene mechanism is also supported by preliminary DFT calculations.     

A New Zn(Ⅱ) Coordination Polymer Constructed from 4-(1H-pyrazol-3-yl)pyridine as Fluorescent Sensor for Fe~(3+)

A new Zn(Ⅱ) coordination polymer, [Zn(4-PP)(1,4-BDC)?(H_2O)]_n(1, 4-PP = 4-(1 H-pyrazol-3-yl)pyridine, 1,4-H_2BDC = 1,4-benzenedicarboxylic acid), has been synthesized and structurally characterized by single-crystal X-ray diffraction as well as elemental analysis, IR spectra, XRPD and TG. Structural analysis reveals that Zn(Ⅱ) ions are bridged by COO-from 1,4-BDC~(2-)to form a binuclear structure as the second building units(SBUs). Zn_2 clusters can be clarified as 4-connected nodes, so the framework of 1 can be considered as a 2 D(44?62)-sql sheet. Fluorescence measurements show that 1 has highly selective and sensitive detection of Fe~(3+) in water medium.     

Composite Membranes Based on the Poly(1-trimethylsylyl-1-propine): Influence of the Porous Aromatic Frameworks Produced from the Friedel–Crafts Reaction and Introduced into the Polymer Matrix

Russian Journal of Applied Chemistry - The effect of particles of porous aromatic frameworks, synthesized by the Friedel–Crafts reaction (PAF-FC), introduced into matrix of glassy polymer...     

Visible-Light-Promoted Formation of C—C and C—P Bonds Derived from Evolution of Bromoalkynes under Additive-Free Conditions:Synthesis of 1,1-Dibromo-1-en-3-ynes and Alkynylphosphine Oxides

The controllable achievement of C—C and C—P bond formations is developed via visible-light-promoted bromoalkyne dimerization or its further transformation with ...     

Reactions of 4,5-bis(morpholin-4-yl)cyclopent-2-en-1-one with sodium salts derived from methyl dichloroacetate and ethyl (dimethyl-λ<Superscript>4</Superscript>-sulfanylidene)acetate

An attempt was made to synthesize fused cyclopropane derivatives suitable for subsequent transformation into vicinal diamino-substituted cyclohexenecarboxylic acids via reactions of 4,5-bis(morpholin-4-yl)cyclopent-2-en-1-one with sodium salts derived from methyl dichloroacetate and ethyl (dimethyl-λ⁴-sulfanylidene) acetate.     

Asymmetric versus symmetric silver–sulfur–nitrogen bonding in the solid-state structure of silver-1-phenyl- 1H-tetrazole-5-thiol: single crystal structure of {[(AgPMT)4 · 0.5THF]} n

The solid-state structure of the highly insoluble silver complex 1-phenyl-1H-tetrazole-5-thiol (AgPMT), without solubilizing ligands, has been successfully resolved. The crystal structure of {[(AgPMT)₄?·?0.5THF]} _n consists of polymeric repeating units of asymmetrically constructed AgPMT dimers. The asymmetric dimers are based on S–Ag–N and N–Ag–N links, and reveal the routes of connectivity possible with this multidentate ligand. This is one of the few linear, one-dimensional silver-based polymers.     

Synthesis and Properties of N,N′-Disubstituted Ureas and Their Isosteric Analogs Containing Polycyclic Fragments: II. N-(4-Oxoadamantan-1-yl)-N′-[fluoro(chloro)phenyl]ureas

Russian Journal of Organic Chemistry - A series of N-(4-oxoadamantan-1-yl)-N′-[fluoro(chloro)phenyl]ureas have been synthesized in 27–73% yields by reaction of...     

Oxazolone versus macrocycle structures for leu-enkephalin b<Subscript>2</Subscript>–b<Subscript>4</Subscript>: Insights from infrared multiple-photon dissociation spectroscopy and gas-phase hydrogen/deuterium exchange

The collision-induced dissociation (CID) products b₂-b₄ from Leu-enkephalin are examined with infrared multiple-photon dissociation (IR-MPD) spectroscopy and gas-phase hydrogen/deuterium exchange (HDX). Infrared spectroscopy reveals that b₂ exclusively adopts oxazolone structures, protonated at the N-terminus and at the oxazolone ring N, based on the presence and absence of diagnostic infrared vibrations. This is correlated with the presence of a single HDX rate. For the larger b₃ and b₄, the IR-MPD measurements display diagnostic bands compatible with a mixture of oxazolone and macrocycle structures. This result is supported by HDX experiments, which show a bimodal distribution in the HDX spectra and two distinct rates in the HDX kinetic fitting. The kinetic fitting of the HDX data is employed to derive the relative abundances of macrocycle and oxazolone structures for b₃ and b₄, using a procedure recently implemented by our group for a series of oligoglycine b fragments (Chen et al. J. Am. Chem. Soc. 2009, 131(51), 18272–18282. doi: 10.1021/ja9030837). In analogy to that study, the results suggest that the relative abundance of the macrocycle structure increases as a function of b fragment size, going from 0% for b₂ to ∼6% for b₃, and culminating in 31% for b₄. Nonetheless, there are also surprising differences between both studies, both in the exchange kinetics and the propensity in forming macrocycle structures. This indicates that the chemistry of “head-to-tail” cyclization depends on subtle differences in the sequence as well as the size of the b fragment.     

A Y(Ⅲ)-organic Coordination Polymer Constructed from 2-(Pyridine-4-yl)-1H-imidazole-4,5-dicarboxylate and Oxalate Ligands: Structure and Luminescent Property

A novel compound, {[Y(HPIDC)(OX)1/2(H2O)]·2H2O}n (1, H3PIDC = 2-(pyridin-4- yl)-1H-imidazole-4,5-dicarboxylic acid, H2OX = oxalic acid), has been synthesized under hydrothermal conditions and characterized by thermal analysis (TGA), powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. Complex 1 crystallizes in monoclinic space group P21/c with a = 8.342(8), b = 14.61(1), c = 11.487(1), β = 90.78(9)°, V = 1400.4(2)3, Z = 4, C11H11N3O9Y, Mr = 418.14, Dc = 1.983 g/cm3, F(000) = 836, Rint = 0.0509, T = 293(2) K, μ = 4.240 mm-1, the final R = 0.0477 and wR = 0.1125 for 2770 observed reflections with I > 2σ(I). Compound 1 exhibits a 3D framework and generates the 1D open channels filled with free water molecules. The structure of 1 can be rationalized as a diamondoid network when the atom yttrium is regarded as a 4-connected node linking four surrounding yttrium atoms. The luminescent property of compound 1 is also investigated.     

A New 1-D Chain ofγ-Hg3S2Br2Constructed from Hg4S4Squares:Solid-state Synthesis,Structure and Optical Properties

A new metal chalcogenide,γ-Hg₃S₂Br₂(1),has been prepared by moderate-temperature solid-state reaction,and its crystal structure was determined by single-crystal X-ray diffraction analysis.Compound 1 crystallizes in space group Cmmm of orthorhombic system with a=9.1923(18),b=18.2262(5),c=4.6251(7)?,V=774.9(3)?³and Z=4.In the structure,two Hg(1),two Hg(2)and four S(1)atoms form a near square Hg₄S₄,and such squares are linked by Hg(3)atoms nearly linearly coordinated to two S1 atoms of two parallel Hg₄S₄squares to form one-dimensional infinite Hg₆S₄chains along c direction.Optical absorption spectra reveal the presence of sharp optical gap of 2.80 eV for 1.IR spectrum,TGA and electric resistivity have been investigated.     

Metal-centered deltahedral Zintl ions: synthesis of [Ni@Sn9]4- by direct extraction from intermetallic precursors and of the vertex-fused dimer [{Ni@Sn8(μ-Ge)(1/2)}2]4-

Ni-centered deltahedral Sn(9) clusters with a charge of 4-, i.e., [Ni@Sn(9)](4-), were extracted in ethylenediamine in high yield directly from intermetallic precursors with the nominal composition "K(4)Sn(9)Ni(3)". The new endohedral clusters were crystallized and structurally characterized in K[K(18-crown-6)](3)[Ni@Sn(9)]·3benzene (1a, triclinic, P1?, a = 10.2754(5) ?, b = 19.5442(9) ?, and c = 20.5576(13) ?, α = 73.927(3)°, β = 79.838(4)°, and γ = 84.389(3)°, V = 3899.6(4) ?(3), Z = 2) and K[K(2,2,2-crypt)](3)[Ni@Sn(9)] (1b, triclinic, P1, a = 15.8028(8) ?, b = 16.21350(9) ?, and c = 20.1760(12) ?, α = 98.71040(10)°, β = 104.4690(10)°, and γ = 118.3890(10)°, V = 4181.5(4) ?(3), Z = 2). The alternative method of a post-synthetic insertion of a Ni atom in empty Sn(9) clusters by a reaction with Ni(cod)(2) predominantly produces the more-oxidized clusters with a charge of 3-, i.e., the recently reported [Ni@Sn(9)](3-). Nonetheless, using substoichiometric amounts of 18-crown-6 as a cation sequestering agent, we also have been able to isolate the 4- clusters as a minor phase from such reactions. They were structurally characterized in K[K(en)][K(18-crown-6)](2)[Ni@Sn(9)]·0.5en (2, monoclinic, P2(1)/n, a = 10.4153(5) ?, b = 25.6788(11) ?, and c = 20.6630(9) ?, β = 102.530(2)°, V = 5394.7(4) ?(3), Z = 2). The ability of the Ni-centered clusters to exist with both 3- and 4- charges parallels the same ability of the empty clusters and is very promising for similarly rich chemistry involving electron transfer and flexible "oxidation states". We also report the synthesis and characterization of the endohedral heteroatomic dimer [{Ni@Sn(8)(μ-Ge)(1/2)}(2)](4-) composed of two [Ni@(Sn(8)Ge)]-clusters fused at the Ge-vertex. The dimer was synthesized by reacting an ethylenediamine solution of a ternary precursor with the nominal composition "K(4)Ge(4.5)Sn(4.5)", which is known to produce heteroatomic Ge(9-x)Sn(x) clusters, with Ni(cod)(2). It is isostructural with the reported [{Ni@Sn(8)(μ-Sn)(1/2)}(2)](4-) and is structurally characterized in [K-(2,2,2-crypt)](4)[{Ni@Sn(8)(μ-Ge)(1/2)}(2)]·2en (3, monoclinic, C2/c, a = 30.636(2) ?, b = 16.5548(12) ?, and c = 28.872(2) ?, β = 121.2140(10)°, V = 12523.5(15) ?(3), Z = 4).     

Enantioselective synthesis of β-amino acids. Part 9: Preparation of enantiopure α,α-disubstituted β-amino acids from 1-benzoyl-2(S)-tert-butyl-3-methylperhydropyrimidin-4-one,

Double alkylation of enantiopure N,N-acetal pyrimidinone (S)-1, a masked chiral derivative of β-alanine prepared from (S)-asparagine, proceeds with high stereoselectivity to give C(5) disubstituted adducts (2S,5R)-6, (2S,5S)-6, (2S,5R)-7, and (2S,5S)-7. Acid hydrolysis of these derivatives affords enantiopure α,α-dialkylated β-amino acids (R)-8, (S)-8, (R)-9, and (S)-9 in very good yields.     

Stereoselective Preparation of 1-[5-O-(tert-Butyldimethylsilyl)-2,3-dideoxy-3-iodo-β-D-threo-pentofuranosyl]thymine from Thymidine: An Efficient Entry to 3′,4′-Unsaturated Nucleoside

The title compound (13) has been synthesized from 5′-O-TBS-thymidine (8) through a highly stereoselective iodination of the 3′-hydroxyl group utilizing I₂/PPh₃/imidazole. This method provides an efficient entry to the 3′,4′-unsaturated derivative (7).     

Synthesis of 3′H-cyclopropa[1,9](C60-I h)[5,6]fullerenes from 2′-aryl-1′,1′-dimethyl-2′,5′-dihydro-1′H-pyrrolo[3′,4′:1,9]-(C60-I h)[5,6]fulleren-1-ium iodides

Russian Journal of Organic Chemistry - New 1′,1′-dimethyl-2′,5′-dihydro-1′H-pyrrolo[3′,4′:1,9](C60-I h)[5,6]fulleren-1-ium iodides containing different...     

A new method for the formation of the imidazo[4′, 5′; 3,4] pyrido[2,3-b]indole ring: Formal synthesis of the alkaloids from marine origin grossularines-1 and 2

A new synthesis of the 2-dimethylamino-4-hydroxy-6-methoxymethyl-3H-imidazo[4′, 5′:3,4] pyrido[2,3-b]indole, used as key intermediate in the total synthesis of the alkaloids grossularines-1 and -2, based on the step-wise formation of the pyridine and imidazole rings, is described.