Synthesis and Characterization of Some Ruthenium Mixed-Ligand Complexes

The complexation reaction of trans-[RuCl₂(Dpte)₂] (Dpte – (diphenylthio)ethane) with mixed diimine ligands 2,2"-bipyridine, pyridylquinoline, 4,6-dichloro-2-(2-pyridyl)pyrimidine, 4,6-dichloro-5-methyl-2-(2-pyridyl)pyrimidine, and 4,6-dichloro-5-phenyl-2-(2-pyridyl)pyrimidine produces new Ru(II) mixed-ligand complexes. These complexes exhibit maximum photo- and chemical stability and high absorptivity. The above complexes have been characterized using IR, ¹H and ¹³C NMR, electronic absorption spectroscopy, and elemental analysis.     

The 6Li,6Li-INADEQUATE Experiment: A New Tool for 1D- and 2D-NMR Studies of Organolithium Compounds

The 1D- and 2D-⁶Li, ⁶Li-INADEQUATE experiments are described as new tools for the detection of scalar coupled nonequivalent ⁶Li nuclei in organolithium clusters. Practical applications of these sequences are demonstrated for the ⁶Li-NMR spectra of (E)-1-lithio-2-(2-lithiophenyl)-1-phenylhex-1-ene ( 1 ) and (E)-2-lithio-1-(2-lithiophenyl)-1-phenylpent-1-ene ( 2 ), where signals due to dimers and monomers can be distinguished. The performance of the 2D-⁶Li, ⁶Li-INADEQUATE and the ⁶Li, ⁶Li-COSY-45-LR experiment are compared. The ⁶Li chemical shifts of 1 and 2 are discussed.     

Some reactions of 1-lithio-2-n-butyl-1,2-dihydropyridine. VI. Synthesis of β-substituted pyridines

Reaction of the ambident anion 1-lithio-2-n-butyl-1,2-dihydropyridine ( 1 ) with several electrophilic reagents has been investigated. Direct methods for the introduction of amino, bromo, β-pyridyl, arylselenyl, alkanesulfonyl and methyl substituents into the β-position of pyridine are described.     

Indole related compounds. Reaction of 1-protected-indoles with pyridine substrates

The products resulting from the reactions of 1-benzenesulfonyl-2-lithioindole and 2-lithio-1-methylindole with different pyridine substrates (pyridine, 1-methoxy-pyridinium salt and 2-bromopyridine) have been studied. The use of lithiocyclohexylisopyropylamide as a lithiating agent of indoles has been investigated. The preparation of four of the possible benzenesulfonyl derivatives of 2-(2′ -pyridyl)indole is described.     

Pyridine-substituted hydroxythiophenes. V. Preparation of 5-(2-, 3-and 4-pyridyl)-2-hydroxythiophenes

5-(2-, 3- and 4-Pyridyl)-2-t-butoxythiophenes have been prepared in very good yields by Pd(0) catalyzed cross-coupling of the three isomeric bromopyridines with 5-trimethylstannyl-2-t-butoxythiophene derived from 2-bromothiophene via 2-t-butoxythiophene. Dealkylation of 5-(2-, 3- and 4-pyridyl)-2-t-but-oxythiophenes with boron trifluoride etherate in dichloromethane at room temperature led to predominant formation of rearranged products, 5-(2- and 3-pyridyl)-3-t-butyl-3-thiolene-2-ones, together with a small amount of 5-(2- and 3-pyridyl)-2-hydroxythiophenes as a mixture of two tautomeric keto forms in the case of the 2-pyridyl and the 3-pyridyl isomers, and exclusive formation of rearranged product in the case of the 4-pyridyl isomer. However, dealkylation of 2-methoxy-5-(2-, 3- and 4-pyridyl)thiophenes, prepared similarly to the 5-(2-, 3- and 4-pyridyl)-2-t-butoxythiophenes, with boron tribromide under the same reaction conditions as above resulted exclusively in the tautomeric mixture of 5-(2- and 3-pyridyl)-3-thiolene-2-ones and 5-(2- and 3-pyridyl)-4-thiolene-2-ones in the case of the 2-pyridyl and 3-pyridyl isomers. In the case of the 4-pyridyl isomer polymerization took place.     

Determination of technetium based on quenching of the fluorescence of some organic compounds,with application to vegetation

Technetium is an effective quencher of the fluorescence produced by 2,5-diphenyloxazole (PPO), 1,4-bis(4-methyl-5-phenyl-2-oxazolyl)benzene (POPOP) and 2,2′-pyridil [1,2-dioxo-1,2-bis(2-pyridyl)ethane]. Spectrofluorimetric procedures for 0.01–12 μg Tc ml^?1 with PPO and 0.1–12 μg ml^?1 with 2,2′-pyridil, and a spectrophotometric method for 1–15 μg ml^?1 are described. The distribution of technetium in vegetation is measured by applying the PPO method.     

The reaction of 1-azirines with 2-pyridyl isothiocyanate: Possible approaches to benzodiazepine and benzodiazepine derivatives

The structure of the dimer ( 5 ) from 2-pyridyl isothiocyanate ( 1 ) has been confirmed by ¹³C nmr spectral studies. The cycloaddition of 2-pyridyl isothiocyanate with 1-azirines results in the formation of thiazoles ( 10 ). Thermal decomposition of the vinyl azide ( 14 ) gives the pyrrole ( 15 ) and the pyridazine ( 16 ) instead of 2-(2-pyridyl)-1-azirine ( 12 ).     

The exchange of chloro and ethoxy groups upon the addition of dimethylchlorosilane to vinyldimethylethoxysilane

The addition of dimethylchlorosilane to vinyldimethylethoxysilane in the presence of chloroplatinic acid yielded 1,2-bis(dimethylchlorosilyl)ethane, 1-(dimethylchlorosilyl)-2-(dimethylethoxysilyl)ethane and 1,2-bis(dimethylethoxysilyl)ethane. The formation of three products is explained on the basis of chloro-ethoxy exchange reactions. Equilibration of the dimethylchlorosilane-vinyldimethylethoxysilane system was investigated using ¹H NMR and gas-liquid chromatography. The equilibrium constants indicated near random behavior for the substituent exchange.     

Reactions of 2-chloro-2-(4-pyridyl)propane with nucleophiles. Substitution on tertiary carbon

The reaction of 2-chloro-2-(4-pyridyl)propane ( 2 ) with lithium 2-propanenitronate affords the C-alkylation product 2-nitro-3-(4-pyridyl)-2,3-dimethylbutane ( 3 ), the Michael-adduct 2-nitro-2-methyl-4-(4-pyridyl)pentane ( 4 ), 4-isopropenylpyridine ( 5 ) and 2-(4-pyridyl)-2-propanol ( 6 ). Of these four products, only the formation of 3 is suppressed when the reaction is performed in the presence of radical inhibitors. The reaction of compound 2 with sodium azide gives the tertiary substitution product 2-azido-2-(4-pyridyl)propane ( 8 ). The reaction is not influenced by radical inhibitors. This is also the case in the reaction of 2 with sodium benzenethiolate, which affords 2-mercaptophenyl-2-(4-pyridyl)propane ( 9 ) and 1-mercaptophenyl-2-(4-pyridyl)propane ( 10 ). Compound 5 , the product of an E₂-type elimination is also formed in the azide and thiolate reactions. A Michael type addition of sodium benzenethiolate to 5 explains the formation of 10 . Similarly, generation of 5 in reactions of 2 with sodium methanethiolate and sodium cyanide accounts for the formation of 1-mercaptomethyl-2-(4-pyridyl)propane ( 11 ) and 3-(4-pridyl)butanenitrile ( 12 ), respectively.     

The influence of perchloric acid on 2,3-dimethylpyrazine and 1,2-bis(4-pyridyl)ethane: crystal structure and Hirshfeld surfaces analysis

2,3-Dimethylpyrazine and 1,2-bis(4-pyridyl)ethane are both N-containing aromatic heterocyclics with two N atoms approximately in the para position. We here report two compounds derived from these heterocyclics (compounds 1 and 2). Compounds 1 and 2 both form a 1:1 2,3-dimethylpyrazine:perchloric acid (PA) and 1,2-bis(4-pyridyl)ethane:PA cocrystal, respectively. Their crystal structures were characterized by single-crystal X-ray diffraction, which revealed that the C–H?O and N–H?O hydrogen bonding interactions were found to stabilize the crystal structure in compounds 1 and 2. However, PA plays a necessary role for the one-dimensional structure in 1 and the three-dimensional structure in 2. Hirshfeld surfaces and fingerprint plots were applied to get the same conclusion.

     

Thermal,spectroscopic, X-ray powder diffraction,and structural studies on a new Cd(II) mixed-ligand coordination polymer

A new coordination polymer derived from Cd(II) with both rigid and flexible spacer ligands trans-1,2-bis(4-pyridyl)ethane (bpa) and 4,4′-bipyridine (4, 4′-bipy), {[Cd(μ-bpa)(4, 4′-bipy)₂(H₂O)₂] · (ClO₄)₂} _n has been synthesized and characterized by elemental analysis, IR-, ¹H NMR spectroscopy and studied by thermal analyses as well as X-ray crystallography. The single crystal X-ray analysis shows that the complex is a 1-D polymer as a result of bridging 1,3-di(4-pyridyl)propane (bpa). The 1-D chains are further self-assembled into a 3-D network via hydrogen bonding and π–π stacking. In this structure the perchlorates fill the voids. Thermal studies of this polymer show step to step separating of ligands and counter ion at different temperatures.     

New mesogens with cubic phases: hydrogen-bonded bipyridines and siloxane-containing benzoic acids I. Preparation and phase behaviour

Several 4-(oligodimethylsiloxyl)alkoxybenzoic acids and their hydrogen-bonded complexes with 4,4-dipyridyl or 1,2-bis(4-pyridyl)ethane were prepared and their phase behaviour studied by DSC and polarized optical microscopy. The neat acids showed no liquid crystalline phases. The 4,4-dipyridyl complex of 4-(n-heptamethyltrisiloxyl)hexyloxybenzoic acid (Si3C6BA) exhibits an optically isotropic, highly viscous liquid crystalline phase below a smectic A phase. The 1,2-bis(4-pyridyl)ethane complex of Si₃C₆BA also shows an optically isotropic liquid crystalline phase above its smectic C phase. Its behaviour is similar to that of the well known cubic D phase found in 4-n-alkoxy-3-nitrobiphenyl-4-carboxylic acids. In the hydrogenbonded mesogens studied herein, the cubic phase appears to assemble spontaneously in order to take account of the chemical incompatibility between the siloxane moiety terminating the H-bonded complex and the stiff aromatic cores. The transition temperatures of the cubic phases in these materials is around 100^oC, hence they are amenable to a variety of physical measurements.     

α-(3-Pyridyl)malonates: preparation and synthetic applications

Alkylation of aromatic rings is a major challenge in organic syntheses since more complex carbon skeletons can be constructed. The alkylation of pyridine by nucleophilic aromatic substitution of the nitro group in methyl 3-nitro-4-pyridylcarboxylate (1) with malonic ester is reported. The versatility of the α-(3-pyridyl) malonic ester product (3) is demonstrated by the formation of a number of new 3-alkylated pyridines and new fused bis-heterocycles. cis 2-Halomethyl-4-(3-pyridyl)tetrahydrofuran products were selectively prepared. Exact ¹H and ¹³C NMR assignments of practically all products were obtained by a series of NMR experiments.     

Benzyne-mediated rearrangement of 3-(2-pyridyl)-1,2,4-triazines into 10-(1H-1,2,3-triazol-1-yl)pyrido[1,2-a]indoles

The reaction between 5-R-6-R¹-3-(2-pyridyl)-1,2,4-triazines and benzyne generated in situ in toluene under reflux results in the formation of 10-(1H-1,2,3-triazol-1-yl)pyrido[1,2-a]indoles 3 in up to 60% yields instead of the expected 3-R-4-R¹-1-(2-pyridyl)isoquinolines 2. The crystal structure of product 3c and the proposed mechanism for the formation of 3 are reported.     

Copper(II) complexes of a series of polypyridine ligands possessing a 1,2-bis(2-pyridyl)ethane common moiety: incorporation and hydrolysis of phosphate esters

Two tetradentate ligands 1,2-bis[2-((dimethylamino)methyl)-6-pyridyl]ethane (L1) and 1,2-bis[2-(N-piperidinomethyl)-6-pyridyl]ethane (L2) and a hexadentate ligand 1,2-bis(2-((methyl(pyridylmethyl)amino)methyl)-6-pyridyl)ethane (L3) were prepared as part of a series of new polypyridine ligands possessing a 1,2-bis(2-pyridyl)ethane common moiety. L1 and L2 form mononuclear Cu(II) complexes [Cu(L)(Cl)](ClO4) [L = L1 (1) and L2 (2)], respectively. L3 forms a dinuclear Cu(II) complex [Cu2(L3)((PhO)2PO2)2](ClO4)2 (3) or a hexanuclear Cu(II) complex [Cu6(L3)3((PhO)PO3)4](ClO4)4 (4) in the presence of (PhO)2PO2- monoanion or (PhO)PO3(2-) dianion, respectively. The structures of 1-4 were determined by X-ray analysis. The structures in solution were investigated by means of FAB and CSI MS spectrometers. The structural flexibility of the common 1,2-bis(2-pyridyl)ethane moiety and of the pendant groups allows complexes 1-4 to adapt to the various structures. Each Cu ion in 1 and 2 adopts a square pyramidal geometry with one Cl ion and two pendant groups (L1 and L2) binding in a bis-bidentate chelate mode. There is no steric repulsion between the pendant groups, so that the ligands specifically stabilize the mononuclear structures. L3 binds two Cu(II) ions with two pendant groups in tridentate chelate modes and, with the incorporation of phosphate esters, various dinuclear units are formed in 3 and 4. In 4, a dinuclear unit of [Cu2(L3)]4+ links two dinuclear units of [Cu2(L3)(PhOPO3)2] with four (mu3)-1,3-PhOPO3(2-) bridges. The hydrolytic activity of 2 and a dicopper(II) complex of L3 was examined with tris(p-nitrophenyl) phosphate (TNP) as a substrate.     

13C NMR coupling constants in delocalized organo-alkali metal compounds. Models of polymerization systems

2,5-Diphenyl-2,5-dipotassiohexane, 2-lithio-4,4-dimethyl-2-phenylpentane, and 1-lithio-2,5,5-trimethylhexene-2 have been prepared, all labelled with¹³C in the position adjacent to the alkali metal atom. The¹³C NMR spectra of these compounds have been measured and the¹³CC coupling constants found for the charged atom. The first two compounds have coupling constants consistent with an sp² hybridized C_α, with relatively little effect of the charge on the coupling constant. The third compound, when dissolved in either THF or benzene, gave much smaller coupling constants, which are more difficult to interpret.     

Pyridine-substituted hydroxythiophenes. II. Alkylation of o-(2-, 3- and 4-pyridyl)-3-hydroxythiophenes: Regiospecific formation of o-pyridyl-3-alkoxythiophenes

The alkylation of o-(2-, 3- and 4-pyridyl)-3-hydroxythiophenes has been investigated. In the case of 4-(2-, 3- and 4-pyridyl)-3-hydroxythiophene systems, the soft alkylating reagent, methyl iodide, using sodium hydride as the base and dimethylimidazolidinone as the solvent, gave rise to a mixture of O-alkylated and O,C-dialkylated products in the proportions of 4.6–6.5 to 1. However, in the case of 2-(2-, 3- and 4-pyridyl)-3-hydroxythiophene systems, the same reaction conditions brought about exclusively O-alkylated compounds in yields of 45–53%. In both cases, the hard alkylating reagent, methyl p-toluenesulfonate, with the same base and solvent, only give O-alkylated compounds in yields of 51–77%. These latter conditions resulted in a good preparative route for the regiospecific formation of o-pyridyl-3-alkoxythiophenes by using ethyl 2-bromopro-pionate as well as methyl p-toluenesulfonate as alkylating reagents. The hydrolysis of the esters, derived from alkylation with ethyl 2-bromopropionate, has also been investigated.     

The mass spectra of some phenyl pyridyl ketones

The mass spectra of phenyl 2-pyridyl, phenyl 3-methoxy-2-pyridyl, phenyl 4-methoxy-2-pyridyl, phenyl 5-methoxy-2-pyridyl, phenyl 6-methoxy-2-pyridyl ketones, phenyl 3-pyridyl and phenyl 6-methoxy-3-pyridyl ketones, and phenyl 4-pyridyl ketone were studied. The major fragmentation pathway of all the ketones results in the formation of[C₆H₅CO]⁺ and [C₅H₄NCO]⁺ type ions. Another fragmentation path is the loss of carbon monoxide with formation of an [M ? CO]⁺ ion after skeletal rearrangement.     

Synthesis and Ldasic Properties of O,O,O-Triethyl-N-(2-Pyridyl) Imidophosphates

Abstract

The phosphorus (111) compounds are known to react readily with arylazides resulting in the formation of imi-dophosphorus compounds (Staudinger reaction)¹.

We nave obtained O,O,O-triethyl-Ii-(2-pyridyl)imido-pnosphates by the reaction of triethylphosphites with 2-pyridylazides (existing as tetrazoles) with a good yield.