Synthesis of some benzimidazole- and benzothiazole-derived ligand systems and their precursory diacids

Procedures are described for the preparation of various bidentate and linear tetradentate benzimidazoles and benzothiazoles incorporating units such as pyridyl and thioether, and for the preparation of certain thioether dicarboxylic acids precursory to them. Condensations of ortho-functinal anilines with carboxylic acids were carried out in polyphosphoric acid or refluxing HCl solution. Syntheses are reported for: [HO₂C(CH₂)2S(CH₂)₂]₂X (X = O, S), 1,9-bis(benzimidazol-2-yl)-2,5,8-trithianonane, 1,11-bis(N-methylbenzimidazol-2-yl)-3,6,9-trithiaundecane, 1,11-bis(2-benzimidazol-2-yl)-6-oxo-3,9-dithiaundecane, 2-(2-pyridyl)benzothiazole, 2,6-bis(benzothiazol-2-yl)pyridine, 2-(2-pyridyl)-N-methylbenzimidazole, 2-(2-pyridylmethyl)benzimidazole and 2-(N-methyl-2-piperidyl)benzimidazole. The compounds were characterized, where appropriate, by their mass, uv and ¹H-nmr spectra.     

Lanthanide Complexes of Polyacid Ligands derived from 2, 6-bis(pyrazol-1-yl)pyridine,pyrazine, and 6, 6′-bis(pyrazol-1-yl)-2, 2′-bipyridine: Synthesis and luminescence properties

The synthesis of three novel pyrazole-containing complexing acids, N,N,N′,N′-{2, 6-bis[3-(aminomethyl)pyrazol-1-yl]-4-methoxypyridine}tetrakis(acetic acid)( 1 ), N,N,N′,N′-{2, 6-bis[3-(aminomethyl)pyrazol-1-yl]pyrazine}-tetrakis(acetic acid) ( 2 ), and N,N,N′,N′-{6, 6′-bis[3-(aminomethyl)pyrazol-1-yl]-2, 2′-bipyridine}tetrakis(acetic acid) ( 3 ) is described. Ligands 1–3 formed stable complexes with Eu^III, Tb^III, Sm^III, and Dy^III in H₂O whose relative luminescence yields, triplet-state energies, and emission decay lifetimes were measured. The number of H₂O molecules in the first coordination sphere of the lanthanide ion were also determined. Comparison of data from the Eu^III and Tb^III complexes of 1–3 and those of the parent trisheterocycle N,N,N′,N′-{2, 6-bis[3-(aminomethyl)pyrazol-l-yl]pyridine}tetrakis(acetic acid) showed that the modification of the pyridine ring for pyrazine or 2, 2′-bipyridine strongly modify the luminescence properties of the complexes. MeO Substitution at C(4) of 1 maintain the excellent properties described for the parent compound and give an additional functional group that will serve for attaching the label to biomolecules in bioaffinity applications.     

Allgemeiner Zugang zu Polyaminen mit Ethan-1,2-diamin-Einheiten: Synthese von nicht natürlich vorkommenden homologen und isomeren N1,4-Di(4-cumaroyl)sperminen

█tl="American"█The synthesis of the three N,N′-di(4-coumaroyl)tetramines, i.e., of (E,E)-N-{3-[(2-aminoethyl)amino]propyl}-3,3′-bis(4-hydroxyphenyl)-N,N′-(ethane-1,2-diyl)bis[prop-2-enamide] ( 1a ), (E,E)-N-{4-[(2-aminoethyl)amino]butyl}-3,3′-bis(4-hydroxyphenyl)-N,N′-(ethane-1,2-diyl)bis[prop-2-enamide] ( 1b ), and (E,E)-N-{6-[(2-aminoethyl)amino]hexyl}-3,3′-bis(4-hydroxyphenyl)-N,N′-(ethane-1,2-diyl)bis[prop-2-enamide] ( 1c ), is described. It proceeds through stepwise construction of the symmetric polyamine backbone including protection and deprotection steps of the amino functions. Their behavior on TLC in comparison with that of 1,4-di(4-coumaroyl)spermine (=(E,E)-N-{4-[(3-aminopropyl)amino]butyl}-3,3′-bis(4-hydroxyphenyl)-N,N′-(propane-1,3-diyl)bis[prop-2-enamide]; 2 ) is discussed.     

The Diyne Reaction of 3, 3′-Bis(phenylethynyl)-2, 2′-bithiophene Derivatives via Rhodium Complexes: A novel approach to condensed benzo[2, 1-b :3, 4-b′]dithiophenes

The syntheses of benzo-fused benzo[2, 1-b:3, 4-b′]dithiophenes 1 and benzo[2, 1-b:3, 4-b′:5, 6-c″]trithiophenes 2 are described. The treatment of easily available 3, 3′-bis(phenylethynyl)-2, 2′-bithiophene derivatives 5a and 6 (via Pd^II-catalyzed alkynylation of the corresponding 3, 3′-dibromo-2, 2′-bithiophenes; see Scheme 1) with chlorotris-(triphenylphosphine)rhodium(I) yields the corresponding cyclic rhodium complexes 7 (Scheme 2) which smoothly react with acetylenes and sulfur to give 1 and 2 in good yields (Schemes 3–5).     

Synthesis and spectral analysis of (±)-cis-N-[1-(2-hydroxy-2-phenyl-ethyl)-3-methyl-4-piperidyl]-N-phenylpropanamide and (±)-cis-N-[1-(2-hydroxy-1-phenylethyl)-3-methyl-4-piperidyl]-N-phenylpropanamide

Treatment of (±)-cis-N-(3-methyl-4-piperidyl)-N-phenylpropanamide (2) with styrene oxide (1) yielded a mixture of (±)-cis-N-[1-(2-hydroxy-2-phenylethyl)-3-methyl-4-piperidyl]-N-phenylpropanamide (3) and (±)-cis-N-[1-(2-hydroxy-1-phenylethyl)-3-methyl-4-piperidyl]-N-phenylpropanamide (4) . The structure of compound 3 was confirmed by an unambiguous synthesis via (±)-cis-N-[1-(2-oxo-2-phenylethyl)-3-methyl-4-piperidyl]-N-phenylpropanamide (6) . The proton and carbon-13 resonances of compounds 3 and 4 were assigned with the aid of two-dimensional heteronuclear correlation experiments.     

Synthesis of 3,3′-biisoxazoles from cyanogen N,N′-dioxide and trimethylsilyl enol ethers via the corresponding 5,5′-bis(trimethylsilyloxy)-3,3′-Δ2-biisoxazolines

Regioselective 1,3-dipolar cycloaddition of Cyanogen N,N′-dioxide ( 2 ) to trimethylsilyl enol ethers 3a-d, 6 and 7 gave the corresponding 5,5′-bis(trimethylsilyloxy)-3,3′-Δ²-biisoxazolines which upon short heating with 10% hydrochloric acid afforded 3,3′-biisoxazoles 5a-d , 8 and 9. Only the intermediate 5,5′-bis(trimethylsilyloxy)-derivative 4a was isolated and studied. Reaction of 2 with vinyl methyl ketone ( 10 ) gave biisoxazoline 11 which by oxidation with γ-manganese dioxide gave biisoxazole 12.     

Preparation of 5-substituted- and 3,5-disubstituted-s-triazolo[4,3-a]pyridines

Cyclization of N-acyl-N′-(6-chloropyrid-2-yl)hydrazines ( 2a-2e ) with phosphorus oxychloride has produced several 5-chloro-s-triazolo[4,3-a]pyridines ( 3a-3e ). Nucleophilic displacement of the chlorosubstituent of 5-chloro-s-triazolo[4,3-a]pyridine ( 3a ) availed the 5-ethoxy ( 4a ) and 5-thioethoxy ( 4b ) derivatives and di(s-triazolo[4,3-a]pyrid-5-yl)sulfide ( 8 ) while reaction of 5-ethylsulfonyl-s-triazolo[4,3-a]pyridine ( 4d ) with potassium hydroxide yielded the 5-hydroxy/5-one system ( 4c or 6 ). Further reaction of 3a with bromine to give 3-bromo-5-chloro-s-triazolo-[4,3-a]pyridine ( 3g ) has provided the corresponding 3-cyano- and 3-carboxamido-5-chloro-s-triazolo[4,3-a]pyridine derivatives ( 3h and 3i ). Treatment of 6-chloro-2-hydrazinopyridine ( 1 ) with cyanogen bromide has provided 3-amino-5-chloro-s-triazolo[4,3-a]pyridine ( 3f ) which, with bromoacetaldehyde dimethyl acetal, transformed into 7-chloroimidazo[1,2-b]-s-triazolo[4,3-a]-pyridine ( 7 ). Finally, attempts at cyclizing N-oxalyl-N′-(6-chloropyrid-2-yl)hydrazine derivatives ( 2g-2i ) with intentions of preparing various 3-acyl-5-chloro-s-triazolo[4,3-a]pyridines for entry into other 3,5-disubstituted systems were unsuccessful.     

Three gemini cationic surfactants as biodegradable corrosion inhibitors for carbon steel in HCl solution

Three gemini cationic surfactants with different hydrophobic spacer chain lengths were synthesized and characterized. The inhibition effect of N,N′-bis(2-hydroxyethyl)-N,N′-dimethyl-N,N′-bis(2-(tetradecanoyloxy)ethyl)ethane-1,2-diaminium bromide (G-2); N,N′-bis(2-hydroxyethyl)-N,N′-dimethyl-N,N′-bis(2-(tetradecanoyloxy)ethyl) hexane-1,6-diaminium bromide (G-6); and N,N′-bis(2-hydroxyethyl)-N,N′-dimethyl-N,N′-bis (2-(tetradecanoyloxy) ethyl) dodecane-1,12-diaminium bromide (G-12) on the corrosion of carbon steel in 1.0 M HCl solution at 25–60 °C was studied by weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy. The results show that the synthesized inhibitors are effective inhibitors even at very low concentration, and the adsorption on the carbon steel surface obeys the Langmuir adsorption isotherm. Potentiodynamic polarization curves reveal that the synthesized inhibitors behave as a mixed-type inhibitor. Adsorption of used inhibitors led to a reduction in the double layer capacitance and an increase in the charge transfer resistance. Thermodynamic parameters have been obtained by adsorption theory. Surface activity and corrosion inhibition relationship were discussed. The biodegradability of the synthesized surfactants showed their readily biodegradation in the open environment and were considered as environmentally friendly corrosion inhibitors.

     

Organic Diodes Based on Redox-Polymer Bilayer-Film-Modified Electrodes

The synthesis of four electropolymerizable 2,2′-bipyridinium salts with tuned reduction potential (E₁^°) is described (N,N′-ethylene-4-methyl-4′-vinyl-2,2′-bipyridinium dibromide ( 4 ; E₁^° ?–0.48 V), 4-methyl-N, N′-(trimethylene)-4′-vinyl-2,2′-bipyridinium dibromide ( 5 ; E₁^°? ?0.66 V), N,N′-ethylene-4-methyl-4′-[2-(1H-pyrrol-1-yl)ethyl]-2, 2′-bipyridinium bis(hexafluorophosphate) ( 6b ; E₁^°? ?0.46 V), and 4-methyl-4′-[2-(1H-pyrrol-1-yl)ethyl]-N, N′-(trimethylene)-2,2′-bipyridinium bis(hexafluorophosphate) ( 7b ; E₁^°? ?0.66 V)). E₁^°-Tuning is based on the torsional angle C(3)–C(2)–C(2′)–C(3′), imposed by the N,N′-ethylene and N,N′-(trimethylene) bridge. The vinylic compounds 4 and 5 undergo cathodic, the pyrrole derivatives 6b and 7b anodic electropolymerization on glassy carbon electrodes from MeCN solutions, yielding thin, surface-confined films with surface concentrations of redox-active material in the range 5 · 10^?9 < Γ < 2.10^?8 mol/cm², depending on experimental conditions. The modified electrodes exhibit reversible ‘diquat’ electrochemistry in pure solvent/electrolyte. Copolymerization of 6b or 7b with pyrrole yields most stable electrodes. Bi ayer-film-modified electrodes were prepared by sequential electropolymerization of the monomers. The assembly electrode/poly- 6b /poly- 7b behaves as a switch, it transforms – as a Schmitt trigger – an analog input signal (the electrode potential) into a digital output signal (redox state of the outer polymer film). Forward-(electrode/poly- 7b /poly- 6b ) and reverse-biased assemblies (electrode/poly- 6b /poly- 7b ) were coupled to the electrochemical reduction of redox-active solution species, e.g. N- (cyanomethyl)-N′-methyl-4,4′-bipyridinium bis(hexafluorophosphate) ( 8 ). Zener-diode-like behavior was observed. Aspects of redox-polymer multilayer-film assemblies, sandwiched between two electronic conductors, are discussed in terms of molecular electronic devices.     

Dissociation energy of N-H bonds in diatomic aromatic amines

The dissociation energies of N-H bonds (D, kJ/mol) were calculated by the intersecting parabolas method using the kinetic data for the following aromatic diamines: para-phenylenediamine (359.8), N,N′-dimethyl-para-phenylenediamine (348.9), N-dimethyl-N′-methyl-para-phenylenediamine (342.4), N,N′-diphenyl-para-phenylenediamine (352.8), N,N′-diphenylethylenediamine (372.7), N,N′-diheptylethylenediamine (373.3), N,N′-di-(4,4′-ethoxyphenyl)ethylenediamine (363.3), N,N′-di-(4,4′-diisopropylphenyl)-para-phenylenediamine (344.6), 4-{[dimethyl(4-phenylamino)phenoxy)silyl]oxy}-N-phenylaniline (353.4), N,N′-di-β-naphthyl-para-phenylenediamine (354.6), N,N′-di-β-naphthoxy-para-phenylenediamine (353.7), 1,1′-dinaphthyl-2,2′-bis-N,N′-phenyldiamine (372.9), 1,1′-dinaphthyl-2,2′-bis-N,N′-β-naphthyldiamine (384.2), and 2,6-bis[(1E)-1-(2-phenylhydrazin-1-ylidene)ethyl]pyridine (367.9). Individual dissociation energies for the two N-H bonds were determined in N-phenyl-N′-isopropyl-para-phenylenediamine: D(PhN-H) = 352.5 and D(Me₂CHN-H) = 348.7 kJ/mol.     

Preparation of polyhydrouracils and polyiminoimidazolidinones

Polyhydrouracils and polyiminoimidazolidinones were prepared by ring formation along the chain of appropriately substituted polyureas. Cyclization of 2-carbomethoxy-ethyl-substituted polyureas in a polyphosphoric acid medium gave the polyhydrouracils. The polyurea precursors were prepared from N,N′-bis(2-carbomethoxyethyl)-1,6-hexanediamine and N,N′-di(2-carbomethoxyethyl)-1,4-cyclohexanebis(methylamine) with methylenebis(4-phenyl isocyanate), 2,4-toluene diisocyanate, and 3,3′-dimethoxy-4,4′-biphenylene diisocyanate. These polyureas were soluble in m-cresol, dimethylformamide, and chloroform, had inherent viscosities of up to 0.8, and could be cast into tough films. The polyhydrouracils had similar physical properties and could also be cast into films. The polyhydrouracils melted at temperatures 100–150°C higher than their polyurea precursors. Polyiminoimidazolidinones were prepared by cyclization of α-cyanoalkyl-substituted polyureas in the presence of n-butylamine. The intermediate polyureas, which were not isolated, were prepared from methylenebis(4-phenyl isocyanate) with N,N′-bis(1-cyanocyclohexyl)-1,6-hexanediamine, N,N′-bis(1-cyanocyclohexyl)-m-xylylenediamine and N,N′-bis(1-cyanocyclopentyl)-1,6-hexanediamine. The polyiminoimidazolidinones were soluble in m-cresol, dimethylformamide, and chloroform and had low inherent viscosities of 0.14–0.28. Thermogravimetric analyses showed that the polyhydrouracils underwent rapid decomposition at 400°C, whereas an analogous unsubstituted polyurea decomposed at 300°C. On the other hand, the polyiminoimid-azolidinones showed no greater thermal stability than the unsubstituted polyurea.     

Co(III) N,N′-diarylformamidine dithiocarbamate complexes: Synthesis,characterization, crystal structures and biological studies

Three symmetric N,N-diarylformamidine dithiocarbamates, N,N′-bis(2,6-dimethylphenyl)formamidine dithiocarbamate (DTL1), N,N′-bis(2,6-disopropylphenyl)formamidine dithiocarbamate (DTL2) and N,N′-dimesitylformamidine dithiocarbamate (DTL3), and three unsymmetric ones, N′-(2,6-dichlorophenyl-N-(2,6-dimethylphenyl)formamidine dithiocarbamate (DTL4), N′-(2,6-dichlorophenyl)-N-(2,6-diisopropylphenyl)formamidine dithiocarbamate (DTL5) and N′-(2,6-dichlorophenyl)-N-mesitylformamidine dithiocarbamate (DLT6), were reacted with chloridocobalt(III) in water to give Co-(DTL1)₃ ( 1 ), Co-(DTL2)₃ ( 2 ), Co-(DTL3)₃ ( 3 ), Co-(DTL4)₃ ( 4 ), Co-(DTL5)₃ ( 5 ) and Co-(DTL6)₃ ( 6 ). All the dithiocarbamates and complexes were characterized using ¹H NMR, ¹³C NMR, Fourier transform infrared, UV–visible and mass spectra and the purity confirmed by elemental analysis. In addition, crystal structures of complexes 1 , 2 , 4 and 5 were determined, confirming the formation of mononuclear species in which the Co(III) centers coordinated to six sulfur atoms from three dithiocarbamate ligands resulting in distorted octahedral geometries. All complexes showed moderate to good antibacterial activities against Gram-negative bacteria Escherichia coli, Salmonella typhimurium, Klebsiella pneumoniae and Pseudomonas aeruginosa even at low concentrations. None of the six were active against Gram-positive bacterium methicillin-resistant Staphylococcus aureus and only active against S. aureus at high concentrations. Complexes 5 and 6 were found to be more active than ciprofloxacin against S. typhimurium, E. coli, P. aeruginosa and K. pneumoniae and complexes with chloro-substituted ligands generally had enhanced activities. Antioxidant activities of the dithiocarbamate salts and their Co(III) complexes were also investigated using DPPH assay and the complexes were found to be more efficient. Complex 2 with an IC₅₀ value of 2.84 × 10⁻⁴ mM displayed the highest activity of all compounds tested, even outdoing ascorbic acid. The radical scavenging ability of the complexes followed the order 2 > 1 > ascorbic acid > 3 > 4 > 6 > 5 .     

On-Line Coupling of High-Performance Liquid Chromatography to Atmospheric Pressure Chemical Ionization Mass Spectrometry (HPLC/APCI-MS and MS/MS). The Pollen Analysis of Hippeastrum x hortorum (Amaryllidaceae)

A H₂O/MeOH extract of the pollen of Hippeastrum x hortorum (Amaryllidaceae) was analyzed. A mixture of different compounds (at the most 84) was found, namely the geometrically ((E,E), (E,Z), (Z,E), and (Z,Z) and structurally isomeric N,N′-dicoumaroyl (=N,N′-bis[3-(4-hydroxyphenyl)prop-2-enoyl]), N,N′-diferuloyl (=N,N′-bis[3-(4-hydroxy-3-methoxyphenyl)prop-2-enoyl]), N,N′-disinapoyl (=N,N′-bis[3-(4-hydroxy-3,5-dimethoxyphenyl)prop-2-enoyl]), N-coumaroyl-N′-feruloyl, and N-feruloyl-N′-sinapoyl derivatives of spermidine (=4-azaoctane-1,8-diamine=N-(3-aminopropyl)butane-1,4-diamine). Their structures were proven by using on-line-coupled high-performance liquid chromatography and atmospheric-pressure chemical-ionization mass spectrometry (HPLC-UV(DAD)/APCI-MS and MS/MS), UV-induced (E)⇌(Z) photoisomerization, and catalytic hydrogenation, as well by comparing their spectra and chromatographic behavior with those of synthetic standards. According to the physicochemical properties of these natural compounds, a proposed biological function is discussed.     

Cycloaddition of Carbodiimides with a Heteroaromatic Substituent to Allenic Acids

Cycloaddition of the allenic acid 3 with the N -cyclohexyl-N′ -heteroaromatic carbodiimides 2a and 2b gave the isomeric pyrido[1,2-a]pyrimidinones 4 and 5 and thiazolo[3,2-a]pyrimidinones 6 and 7 , respectively, instead of the expected Diels-Alder adducts analogous to 1 . The compounds of the latter type, i.e. 8 and 9 , were formed from 3 and carbodiimides 2c and 2d , respectively, containing an N′-(pyrazin-2-yl) or N′-(pyrimidin-2-yl) substituent.     

SYNTHESIS AND NMR SPECTROSCOPIC STUDY OF NEW 5-METHYLFURYL-CONTAINING SCHIFF BASES AND RELATED BIS(AMINOPHOSPHONATES)

The synthesis of three novel 5-methylfuryl-containing Schiff bases: N,N′-bis(5-methylfurfurylidene)-4,4′-diaminodiphenylmethane, N,N′-bis(5-methylfurfurylidene)-1,4-phenylenediamine, and N,N′-bis(5methylfurfurylidene)benzidine and the corresponding bis(aminophosphonates) derived from them, 4,4′-bis{N-methyl(diethoxyphosphonyl)-1-[(5-methyl)-2-furyl]} diaminodiphenylmethane, 1,4-bis { N-methyl(diethoxyphosphonyl)-1-[(5-methyl)-2-furyl]} diaminobenzene, and bis{N-methyl(diethoxyphosphonyl)-1-[(5-methyl)-2-furyl]}- benzidine, is reported. The compounds have been characterized by elemental analysis, TLC, IR, and NMR ( ¹ H, ¹³ C, and ³¹ P) spectra. For comparison, new ¹³ C and ³¹ P NMR data of three furyl-containing analogues of the above bis(aminophosphonates) are also regarded. The NMR studies of the two series of bis(aminophosphonates) reveal the presence of one diastereomer (meso or racemic form).     

Synthesis of endo,exo-7,8,9,10-tetrachlorobicyclo[4.4.0]deca-7,9-diene-3,4-dicarboxylic acid N,N′-bisimides

A one-stage synthesis was developed of N,N′-(3,3′-dimethoxy-4,4′-diphenylmethane)- and N,N′-(1,2-ethane)-endo,exo-7,8,9,10-tetrachlorobicyclo[4.4.0]deca-7,9-diene-3,4-dicarboxylic acids bisimides by reaction of a bisadduct of 1,8,9,10,11,11-hexachlorotricyclo[6.2.1.0^5,10]-undec-9-ene-4,5-dicarboxylic acid N,N′-R-bisimide with pyridine in DMF. The spatial structure of compounds obtained was established.     

Preparation of 2-aryl and 2-aryloxymethyl imidazo[1,2-a]pyridines and related compounds

A series of substituted 2-aryl imidazo[1,2-a]pyridines has been prepared in which a variety of substituents are introduced on the 4′-position of the phenyl ring and on the 3, 5 , 6 or 7 position of the heterocyclic ring. Most examples have acetamido, bromo, cyano, or formyl substituents at the 4′-position. Analogous imidazo-[2,1-b]fhiazoles and imidazo[1,2-a]pyrimidines have also been prepared. Another series of compounds consisting of 4′-formylphenoxymethyl derivatives of imidazole, the three positional isomers of pyridine, thiazole, benzimidazole and ring-substituted imidazo[1,2-a]pyridines has been prepared. 2-(4′-Formylphenylethenyl) derivatives of imidazole and imidazo[1,2-a]pyridine were also prepared.     

Regioselective Transformations of 2′,3′-Seconucleosides into Anhydro Structures and Chiral Crown Ethers

Intramolecular cyclisation of properly protected and activated derivatives of 2′,3′-secouridine ( = 1-{2-hydroxy-1-[2-hydroxy-1-(hydroxymethyl)ethoxy]-ethyl}uracil; 1 ) provided access to the 2,2′-, 2,3′-, 2,5′-, 2′,5′-, 3′,5′-, and 2′,3′-anhydro-2′,3′-secouridines 5, 16, 17, 26, 28 , and 31 , respectively (Schemes 1–3). Reaction of 2′,5′-anhydro-3′-O-(methylsulfonyl)- ( 25 ) and 2′,3′-anhydro-5′-O-(methylsulfonyl)-2′,3′-secouridine ( 32 ) with CH₂CI₂ in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene generated the N(3)-methylene-bridged bis-uridine structure 37 and 36 , respectively (Scheme 3). Novel chiral 18-crown-6 ethers 40 and 44 , containing a hydroxymethyl and a uracil-1-yl or adenin-9-yl as the pendant groups in a 1,3-cis relationship, were synthesized from 5′-O-(triphenylmethyl)-2′,3′-secouridine ( 2 ) and 5′-O,N⁶-bis(triphenylmethyl)-2′,3′-secoadenosine ( 41 ) on reaction with 3,6,9-trioxaundecane-1,11-diyl bis(4-toluenesulfonate) and detritylation of the thus obtained (triphenylmethoxy) methylcompound 39 and 43 , respectively (Scheme 4).     

Strained Ruthenium Complexes Bearing Tridentate Guanidine-Derived Ligands

The dimer [{(η⁶-p-cymene)RuCl}₂(μ-Cl)₂] (cymene=MeC₆H₄ⁱPr) reacts with N,N′-bis(p-tolyl)-N′′-(2-pyridinylmethyl)guanidine ( H₂L1 ) and N,N′-bis(p-tolyl)-N′′-(2-diphenylphosphanoethyl)guanidine ( H₂L2 ), in the presence of NaSbF₆, giving rise to chlorido compounds of formula [(η⁶-p-cymene)RuCl( H₂L )][SbF₆] ( H₂L = H₂L1 ( 1 ), H₂L2 ( 2 )) in which the guanidine ligand adopts a κ² chelate coordination mode. The related ligand (S)-N,N′-bis(p-tolyl)-N′′-(1-isopropyl, 2-diphenylphosphano ethyl)guanidine ( H₂L3 ) affords mixtures of the corresponding chlorido compound [(η⁶-p-cymene)RuCl( H₂L3 )][SbF₆] ( 3 ) together with the complexes [(η⁶-p-cymene)RuCl₂( H₃L3 )][SbF₆] ( 4 ) and [(η⁶-p-cymene)Ru(κ³N,N′,P- HL3 )][SbF₆] ( 10 ) which contain phosphano-guanidinium and phosphano-guanidinate ions acting as monodentate and tridentate ligand, respectively. Compounds 1 , 2 and mixture of 3 / 4 / 10 react with AgSbF₆ rendering the cationic aqua-complexes [(η⁶-p-cymene)Ru( H₂L )(OH₂)][SbF₆]₂ ( H₂L = H₂L1 ( 5 ), H₂L2 ( 6 ), H₂L3 ( 7 )). These aqua-complexes exhibit a temperature-dependent fluxional process in solution. Experimental NMR studies and DFT theoretical calculations on complex 6 suggest that the process involves the exchange between two rotamers around one of the C−N guanidine bonds. Treatment of 5 – 7 with NaHCO₃ renders the complexes [(η⁶-p-cymene)Ru(κ³N,N′,N′′- HL1 )][SbF₆] ( 8 ) and [(η⁶-p-cymene)Ru(κ³N,N′,P- HL )][SbF₆] ( HL = HL2 ( 9 ), HL3 ( 10 )), respectively, in which the HL ligand adopts a fac κ³ coordination mode. The new complexes have been characterized by analytical and spectroscopic means, including the determination of the crystal structures of the compounds 1 , 2 , 5 , 9 and 10 , by X-ray diffractometric methods.     

Polycyclic azines. III. Synthesis of 3-aminoimidazo[1,5-a]pyridine derivatives by cyclodesulfurization of N′-Substituted-N-(2-pyridylmethyl)thioureas with dicyclohexylcarbodiimide

A series of 3-substituted aminoimidazo[1,5-a]pyridine derivatives have been synthesized by cyclodesulfurization of a variety of N′-substituted-N-(2-pyridylmethyl)thioureas with dicyclohexylcarbodiimide (DCCD). ¹H Nmr spectral analysis of all synthesized compounds is given.