Structural characterization of a copper(II) complex containing oxidative cyclization of N-2-(4-picolyl)-N′-(4-methoxyphenyl)thiourea,new ligands of 4-picolylthiourea derivatives and the precursor molecular structure of oxidative cyclization of N-(2-pyridyl)-N′-(4-methoxyphenyl)thiourea

Three new compounds of aryl thiourea derivatives, namely N-2-(4-picolyl)-N′-(4-methoxyphenyl)thiourea (L1), N-2-(6-picolyl)-N′-(4-methoxyphenyl)thiourea (L2) and N-2-(4-picolyl)-N′-(4-nitrophenyl)thiourea (L3), and the new copper(II) complex [Cu(4PicTz4OMePh)(OAC)(EtOH)] (C1), as a result of oxidative cyclization of the ligand (L1), were synthesized. In addition, pure precursor (P1), as the product of the oxidative cyclization of N-(2-pyridyl)-N′-(4-methoxyphenyl)thiourea (L4), was isolated and characterized. Ligands (L1) and (L2) were characterized by ¹H and ¹³C NMR and single crystal X-ray analysis. ¹H NMR spectroscopy showed strong hydrogen bonding interactions between N′H-functionalities and the pyridine nitrogen atoms as well as weak intermolecular hydrogen bonding between the thione sulfur and the NH hydrogen. Structural studies of complex (C1) showed that the copper ion is five-coordinated with a square-pyramidal environment. The oxidative cyclization of ligand (L1) results in an anionic bidentate ligand in complex (C1). Both ligand (L1) and precursor (P1) crystallize as centrosymmetric dimers.     

An approach to the synthesis of chemically modified bisazocalix[4]arenes and their extraction properties

Bisazocalix[4]arenes [N,N′-bis(5-azo-25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene)benzene (1), N,N′-bis(5-azo-25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene)biphenyl (2) and N,N′-bis(5-azo-25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene)-2,2′-dinitro biphenyl (3)] have been synthesized from 25,26,27-tribenzoyloxy-28-hydroxycalix[4]arene by diazocoupling with the corresponding aromatic diamines (p-phenylenediamine, 4,4′-diamino biphenyl and 4,4′-diamino-2,2′-dinitrobiphenyl). Extraction studies of bisazocalix[4]arenes 1, 2, and 3 show no difference in their extraction behavior and selectivity, whereas azocalix[4]arenes are a poor extractant for heavy metal cations. The absorption spectra of the prepared bisazocalix[4]arenes are discussed, both the effect of varying pH and solvent upon the absorption ability of bisazocalix[4]arenes.     

Syntheses and structural characterization of some mono- and di-p-nitrophenyl[3]ferrocenophanes: X-ray structure of [3]ferrocenophane, 3-p-nitrophenyl[3]ferrocenophane, and 3,4′-bis-(p-nitrophenyl)[3]ferrocenophane; DFT calculations on ferrocene derivatives

[3]Ferrocenophane (3a) reacts in a Gomberg reaction with diazotized p-nitroaniline to give a mixture of mono- and di-substituted products. The isomeric pairs of 3- and 2-(p-nitrophenyl)[3]ferrocenophanes (4 and 5), as well as 3,4′- and 3,4-bis-(p-nitrophenyl)[3]ferrocenophanes (6 and 7) were separated from the mixture by column chromatography on Al₂O₃ and characterized by means of mass, IR, UV, ¹H-NMR spectroscopy, and by X-ray analysis (4 and 6). PM3/tm and density functional theoretical calculations on ferrocene (1) and ferrocenophane derivatives are reported. A refined X-ray structure determination of [3]ferrocenophane (3a) is given.     

Novel optically active poly(amide-imide)s from N,N-(4,4-carbonyldiphthaloyl)-bis-l-phenylalanine diacid chloride and aromatic diamines by microwave irradiation

3,3^′,4,4^′-benzophenonetetracarboxylic dianhydride (4,4^′-carbonyldiphthalic anhydride) (1) was reacted with l-phenylalanine (2) in a mixture of acetic acid and pyridine (3:2) and the resulting imide-acid [N,N^′-(4,4^′-carbonyldiphthaloyl)-bis-l-phenylalanine diacid] (4) was obtained in high yield. The compound (4) was converted to the N,N^′-(4,4^′-carbonyldiphthaloyl)-bis-l-phenylalanine diacid chloride (5) by reaction with thionyl chloride. A new facile and rapid polycondensation reaction of this diacid chloride (5) with several aromatic diamines such as 4,4^′-diaminodiphenyl methane (6a), 2,4-diaminotoluene (6b), 4,4^′-sulfonyldianiline (6c), p-phenylenediamine (6d), 4,4^′-diaminodiphenylether (6e), m-phenylenediamine (6f), benzidine (6g) and 2,6-diaminopyridine (6h) was developed by using a domestic microwave oven in the presence of a small amount of a polar organic medium such as o-cresol. The polymerization reactions proceeded rapidly, compared with the conventional solution polycondensation, and was completed within 7 min, producing a series of optically active poly(amide-imide)s with high yield and inherent viscosity of 0.22-0.52 dl/g. All of the above polymers were fully characterized by IR, elemental analyses and specific rotation. Some structural characterization and physical properties of this optically active poly(amide-imide)s are reported.     

Unidirectional α-cyclodextrin-based [2]rotaxanes bearing viologen unit on axle

1-(2-Carboxyethyl)-1′-(10-carbazole-9-yl-decyl)-4,4′-bipyridinium dibromide 2 forms a unidirectional [2]pseudorotaxane with α-cyclodextrin (α-CD) in water. Condensation of 2/α-CD [2]pseudorotaxane with 4-amino-1-naphthalenesulfonate or 6-amino-β-CD provided the unidirectional [2]rotaxanes 3 and 4, in which the secondary face of α-CD is oriented toward the viologen moiety. The structures were elucidated from two-dimensional ROESY and circular dichroism spectra.     

One-pot synthesis of macrocyclic compounds possessing two cyclobutane rings by sequential inter- and intramolecular [2+2] photocycloaddition reactions

Sensitized photocycloaddition reactions of 6,6′-dimethyl-4,4′-[1,3-bis(methylenoxy)phenylene]-di-2-pyrone (1) with electron-poor α,ω-diolefins such as ethylene diacrylate (2a) and polyoxyethylene dimethacrylates (2b-d) afforded site- and stereoselective macrocyclic dioxatetralactones (3a-d) and (4b) having 18- to 25-membered rings across the C5-C6 and C5′-C6′ double bonds, or C5-C6 and C3′-C4′ double bonds in 1, respectively. Similar photoreactions of 1 with electron-rich α,ω-diolefins such as poly(ethylene glycol)divinyl ether (2e and 2f) afforded crown ether-type macrocyclic compounds (5e and 5f) having 18- and 21-membered rings across the C3-C4 and C3′-C4′ double bonds in 1, respectively. The stereochemical features of 3b, 5e-xx, and 5e-nn were determined by the X-ray crystal analysis. The reaction mechanism was inferred by MO methods.     

Synthesis and electrochemistry of novel heteronuclear Fe-Ru bi- and quatermetallocenes, conjugatively connected by ethene and thiophene bridges

(E)-2-(1′-Formylruthenocenyl)ethenyl-1′,2,2′,3,3′,4,4′,5-octamethylferrocene (1) and (all-E)-2,5-bis[2-[1′-[2-(1′,2,2′,3,3′,4,4′,5-octamethylferrocenyl)ethenyl]ruthenocenyl]ethenyl]thiophene (2) were synthesized by a sequence of Wittig olefinations. The X-ray structure of 1 is reported. The cyclic voltammogram of compound 1 shows the irreversible one-electron transfer expected for ruthenocene and a reversible wave for the octamethylferrocene moiety. Both waves occur at about the same potential as observed for the parent metallocenes. Compound 2, however, exhibits completely unusual redox properties. In contrast to most ruthenocene-containing compounds, a reversible two-electron transfer is observed at a significantly lower potential than found usually for ruthenocenes that can be attributed unambiguously to the independent oxidation/reduction of the two ruthenocene moieties. The unexpected stability of the oxidation products must be due to the presence of the thiophene-ethene bridge, which facilitates the oxidation reaction and stabilizes the reaction products by delocalization of the valence electrons.     

Phosphite ligands derived from distally and proximally substituted dipropyloxy calix[4]arenes and their palladium complexes: Solution dynamics, solid-state structures and catalysis

Two bisphosphite ligands, 25,27-bis-(2,2′-biphenyldioxyphosphinoxy)-26,28-dipropyloxy-p-tert-butyl calix[4]arene (3) and 25,26-bis-(2,2′-biphenyldioxyphosphinoxy)-27,28-dipropyloxy-p-tert-butyl calix[4]arene (4) and two monophosphite ligands, 25-hydroxy-27-(2,2′-biphenyldioxyphosphinoxy)-26,28-dipropyloxy-p-tert-butyl calix[4]arene (5) and 25-hydroxy-26-(2,2′-biphenyldioxyphosphinoxy)-27,28-dipropyloxy- p-tert-butyl calix[4]arene (6) have been synthesized. Treatment of (allyl) palladium precursors [(η³-1,3-R,R′-C₃H₄)Pd(Cl)]₂ with ligand 3 in the presence of NH₄PF₆ gives a series of cationic allyl palladium complexes (3a-3d). Neutral allyl complexes (3e-3g) are obtained by the treatment of the allyl palladium precursors with ligand 3 in the absence of NH₄PF₆. The cationic allyl complexes [(η³-C₃H₅)Pd(4)]PF₆ (4a) and [(η³-Ph₂C₃H₃)Pd(4)]PF₆ (4b) have been synthesized from the proximally (1,2-) substituted bisphosphite ligand 4. Treatment of ligand 4 with [Pd(COD)Cl₂] gives the palladium dichloride complex, [PdCl₂(4)] (4c). The solid-state structures of [{(η³-1-CH₃-C₃H₄)Pd(Cl)}₂(3)] (3f) and [PdCl₂(4)] (4c) have been determined by X-ray crystallography; the calixarene framework in 3f adopts the pinched cone conformation whereas in 4c, the conformation is in between that of cone and pinched cone. Solution dynamics of 3f has been studied in detail with the help of two-dimensional NMR spectroscopy.The solid-state structures of the monophosphite ligands 5 and 6 have also been determined; the calix[4]arene framework in both molecules adopts the cone conformation. Reaction of the monophosphite ligands (5, 6) with (allyl) palladium precursors, in the absence of NH₄PF₆, yield a series of neutral allyl palladium complexes (5a-5c; 6a-6d). Allyl palladium complexes of proximally substituted ligand 6 showed two diastereomers in solution owing to the inherently chiral calix[4]arene framework. Ligands 3, 6 and the allyl palladium complex 3f have been tested for catalytic activity in allylic alkylation reactions.     

Acetamidine complexes as catalysts for ethylene polymerization

The reaction of (2,6-diisopropyl-phenyl)-acetimidoyl chloride or (2,6-dimethyl-phenyl)-acetimidoyl chloride with 2,6-dimethylaniline in the presence of triethylamine yields a mixture of isomers N′-(2,6-diisopropyl-phenyl)-N-[1-(2,6-diisopropyl-phenylimino)-ethyl]-N-(2,6-dimethyl)-acetamidine (1a) and N-(2,6-diisopropyl-phenyl)-N-[1-(2,6-diisopropyl-phenylimino)-ethyl]-N′-(2,6-dimethyl)-acetamidine (1b), and N,N′-bis-(2,6-dimethyl-phenyl)-N-[1-(2,6-dimethyl-phenylimino)ethyl)]-acetamidine (2), respectively. The addition of isomers (1a + 1b) to nickel (II) dibromide 2-methoxyethyl ether, (NiBr₂[O(C₂H₄OMe)₂]) gives a mixture of new nickel complexes, [NiBr₂{N′-(2,6-diisopropyl-phenyl)-N-[1-(2,6-diisopropyl-phenylimino)-ethyl]-N-(2,6-dimethyl)-acetamidine}] (3a) and [NiBr₂{N-(2,6-diisopropyl-phenyl)-N-[1-(2,6-diisopropyl-phenylimino)-ethyl]-N′-(2,6-dimethyl)-acetamidine}] (3b). Similarly, ligand 2 reacts with nickel (II) dibromide 2-methoxyethyl ether to afford the complex [NiBr₂{N,N´-bis-(2,6-dimethyl-phenyl)-N-[1-(2,6-dimethyl-phenylimino)ethyl)]-acetamidine}] (4). The structures of the ligands and nickel complexes have been determined by single crystal X-ray diffraction.The addition of MAO to these complexes generates catalytically active species for the homopolymerization of ethylene. The polymer products are high molecular weight (80-169 K). At temperatures of up to 60 °C both catalysts are a single site giving a monomodal molecular weight distribution. However, at 70 °C the mixture (3a + 3b) shows a bimodal molecular weight distribution.     

Synthesis and characterization of novel trans-3-benzyl/(diphenyl)methyl/naphthyl seleno substituted monocyclic β-lactams: X-ray structure of trans-1-(4′-methoxyphenyl)-3-(diphenyl)methylseleno-4-(4′-methoxyphenyl)azetidin-2-one

Several novel trans-3-benzyl/(diphenyl)methyl/naphthylseleno substituted monocyclic β-lactams (5-7) have been synthesized in high yields. The reaction scheme inolves [2 + 2] cycloaddition (Staudinger) reaction between suitably substituted imines 4(a-h) and ketenes (B) accessed from 2-benzyl/(diphenyl)methyl/naphthylselenoethanoic acids (1-3) using POCl₃ and triethylamine in refluxing toluene. Characterization of these newly synthesized seleno substituted β-lactams has been performed by various spectroscopic techniques viz. NMR (¹H, ¹³C and ⁷⁷Se), FTIR, mass spectrometry and elemental analysis. The molecular structure of trans-1-(4′-methoxyphenyl)-3-(diphenyl)methylseleno-4-(4′-methoxyphenyl)azetidin-2-one (6b) has also been established with the help of single crystal X-ray analysis.     

Asymmetric Friedel-Crafts alkylation of activated benzenes with methyl (E)-2-oxo-4-aryl-3-butenoates catalyzed by [Pybox/Sc(OTf)3]

The asymmetric Friedel-Crafts reaction between methyl (E)-2-oxo-4-aryl-3-butenoates (1a-c) and activated benzenes (2a-d) has been efficiently catalyzed by the Sc^III triflate complex of (4′S,5′S)-2,6-bis[4′-(triisopropylsilyl) oxymethyl-5′-phenyl-1′,3′-oxazolin-2′-yl]pyridine (pybox 3). The 4,4-diaryl-2-oxo-butyric acid methyl esters (4) are usually formed in good yields and the enantioselectivity is up to 99% ee. The sense of the stereoinduction can be rationalized with the same octahedral complex (10) between 1, pybox 3 and Sc triflate already proposed for other reactions involving pyruvates, and catalyzed by the same complex.     

A series of metal-organic frameworks constructed with arenesulfonates and 4,4′-bipy ligands

Five transition metal compounds containing arenesulfonates and 4,4′-bipy ligands, namely [Zn₂(N,N′-4,4′-bipy)(N-4,4′-bipy)₂(H₂O)₈](bpds)₂ · 5H₂O (1), [Ag₂(N,N′-4,4′-bipy)₂(bpds)] (2), [Cd(N,N′-4,4′-bipy)(H₂O)₄]₂(4-abs)₄ · 5H₂O (3), [Cu(N,N′-4,4′-bipy) (O-bs)₂(H₂O)₂] · 4H₂O (4), and [Zn(N,N′-4,4′-bipy)₂(H₂O)₂](4,4′-bipy)(bs)₂ · 4H₂O (5) (4,4′-bipy = 4,4′-bipyridine, bpds = 4,4′-biphenyldisulfonate, 4-abs = 4-aminobenzenesulfonate, bs = benzenesulfonate), have been synthesized and characterized by X-ray single crystal diffraction, elemental analyses and TG analyses, in order to investigate the coordination chemistry of arenesulfonates and 4,4-bipy, as well as to construct novel coordination frameworks via mixed-ligand strategy. Compounds 2, 4 and 5 could be obtained via hydrothermal or aqueous reactions. Compound 1 forms a binuclear octahedral metal complex. Compounds 2–4 form polymeric chains. Compound 5 consists of 2D square grids with one intercalated 4,4′-bipy molecule. Weak Ag–Ag interactions are observed in compound 2. These complexes show great structural varieties and there are three different coordination modes observed for both the 4,4′-bipy and the sulfonate ligands.     

A new synthetic procedure to spiro[cyclohexane-1,3′-indoline]-2′,4-diones

A new synthetic pathway to spiro[cyclohexane-1,3′-indoline]-2′,4-diones was found starting from 3-chloromethylene-2-indolones 1 and Danishefsky's diene 2. Their synthesis consists of several steps involving the formation of the cycloadducts, the 6-chloro-4-trimethylsilyloxy-2-methoxyspiro[cyclohex-3-en-1,3′-indolin]-2′-one derivatives, transformed into spiro[cyclohexa-2,5-dien-1,3′-indoline]-2′,4-diones via 6-chloro-spiro[cyclohex-2-en-1,3′-indoline]-2′,4-dione intermediates. The reduction of spiro[cyclohexa-2,5-dien-1,3′-indoline]-2′,4-diones gave spiro[cyclohexane-1,3′-indoline]-2′,4-diones 7. Using a ‘one pot reaction’, starting from 1 and 2, compounds 7 were obtained in satisfactory overall yield.     

Synthesis, single crystal X-ray structure and optical properties of 3,4-dimethyl-dithieno[2,3-b:3′,2′-d]thiophene-7,7-dioxide

The synthesis of the title compound (4), starting from commercial 3-bromo-4-methylthiophene, is described. The single crystal packing mode of 4, as well as the absorption and photoluminescence properties in solution and in the solid state are reported and analyzed in relation to those of the isomeric 3,5-dimethyl-dithieno[3,2-b:2′,3′-d]thiophene-4,4-dioxide (7). The different reactivities of 4 and 7 towards bromination are analyzed in the light of the results of ab initio B3LYP/6-31G^∗ calculations on both compounds.     

Ullmann coupling reaction of 1,3-bistriflate esters of calix[4]arenes: facile syntheses of monoaminocalix[4]arenes and 4,4′:6,6′-diepithiobis(phenoxathiine)

Treatment of 1,3-bistriflate esters of thiacalix- (6a) and calix[4]arenes 6b with benzylamine in the presence of CuI and K₃PO₄ results in the displacement of a TfO moiety with a benzylamino group, which provides an easy access to monoaminothiacalix[4]arene 4a and its methylene-bridged counterpart 4b. On the other hand, the reaction of 6a in the absence of benzylamine leads to intramolecular dietherification, giving 4,4′:6,6′-diepithiobis(phenoxathiine) 7a.     

Microwave-assisted rapid synthesis of novel optically active poly(amide-imide)s containing hydantoins and thiohydantoins in main chain

Rapid and highly efficient synthesis of novel optically active poly(amide-imide)s (PAIs) 6(a-f) was achieved using microwave irradiation. These were made from the polycondensation reactions of 4,4^′-carbonyl-bis(phthaloyl-l-alanine) diacid chloride [N,N^′-(4,4^′-carbonyldiphthaloyl)] bisalanine diacid chloride 5 with six different derivatives of hydantoin and thiohydantoin compounds 4(a-f) in the presence of a small amount of a nonpolar organic medium that acts as a primary microwave absorber. Hydantoin and thiohydantoin derivatives 4(a-e) were synthesis from the reactions between benzil or benzil derivatives 3(a-e) with urea and thiourea. 5,5-Dimethylhydantoin 4f was synthesis from the reactions between acetone cyanohydrin 3f and ammonium carbonate. The polycondensation proceeded rapidly, and was completed within 10 min giving a series of PAIs with an inherent viscosity about 0.25-0.45 dL/g. The resulting PAIs 6(a-f) were obtained in a high yield and were optically active and thermally stable. All of the above compounds were fully characterized by means of Fourier transform infrared spectroscopy, elemental analyses, inherent viscosity (η_inh), solubility tests and specific rotation. Thermal properties of the PAIs 6(a-f) were investigated using thermal gravimetric analysis.     

Synthesis of new acyclic nucleoside phosphonates (ANPs) substituted on the 1′ and/or 2′ positions

A series of 2′ functionalized acyclic nucleoside phosphonate derivatives of 1-[3′-(phosphonomethoxy)propyl]uracil (1-4) have been synthesized together with the 1′ and 2′-ethynyl derivatives of 9/1-[2′-(phosphonomethoxy)ethyl]adenine/thymine (5-7). Key intermediates leading to the latter series are (±)-[2-{diethyl(phosphonomethoxy)}-1-hydroxy]-but-3-yne (25) and (±)-diisopropyl{[2-hydroxy-4-(trimethylsilyl)but-3-yn-1-yl]oxy}methylphosphonate (30). Compounds 25 and 30 are easily obtained starting from (±)-solketal.     

Solid-state photocycloaddition of 6,6′-dimethyl-4,4′-[bis(methylenoxy)phenylene]-di-2-pyrones with benzophenone

Photocycloaddition reactions of 6,6′-dimethyl-4,4′-[bis(methylenoxy)phenylene]-di-2-pyrones (4a-c) with benzophenone (2a) by mixing in the solid state (solid solution) afforded the corresponding oxetane derivatives (5a-c; 1:2 adducts) with high site- and regioselectivity across the C5-C6 and C5′-C6′ double bonds in 4 via the triplet excited state of benzophenone. The oxetane formation proceeded more effectively in the solid state than in solution. The reaction mechanism was inferred by MO methods to be initiated by electrostatic interaction between the C6 position of 4a-c and the carbonyl oxygen of 2a in their ground states. The solid-state interaction may be enhanced by the electron density at the carbonyl oxygen of the triplet 2a. The transition state (TS) analysis of the [2+2] cycloaddition reactions also suggested some triplet complexes and high regioselectivity. The hydrogen-bonding interaction between 2a and 4a-c and the triplet reaction mechanism were also explained by the IR analyses and the quenching experiments, respectively.     

Amberlyst 15 catalyzed synthesis of indole-pyrazole based tri(hetero)arylmethanes

An expedient synthesis of 1,3-diaryl-4-(3,3′-diindolyl)methylpyrazoles 3a-m has been developed using Amberlyst 15 catalyzed condensation of 1,3-diaryl-4-formyl pyrazoles 2 with indoles 1. This reaction was further extended to the synthesis of 4,4′-bis(3,3′-diindolyl)methylphenoxy-alkanes 5a-b by coupling of 4,4′-di(formylphenoxy)alkane 4 with indole 1.     

Synthesis of N,N′-bis and N,N,N′,N′-tetra-[(3,5-di-substituted-1-pyrazolyl)methyl]para-phenylenediamines: new candidate ligands for metal complex wires

A series of tridentate ligands N,N-bis-[(di-substituted-1-pyrazolyl)methyl]arylamines 2-3a,b and benzylamine 4a,b, tetradentate N,N′-bis-[(di-substituted-1-pyrazolyl)methyl]para-phenylenediamines 7a,b and hexadentate N,N,N′,N′-tetra-[(di-substituted-1-pyrazolyl)methyl]para-phenylenediamines 8a,b has been prepared in good yield by condensation of arylamines, benzylamine or para-phenylenediamine with N-hydroxymethyl disubstituted pyrazoles 1a,b. The synthesis and characterisation of these various polydentate ligands are described.