Synthesis and anion recognition properties of 8,8′-dithioureido-2,2′-binaphthalene

A novel artificial receptor based on 2,2′-binaphthalene skeleton bearing two thiourea groups was prepared via nickel(II)-catalyzed homocoupling of the corresponding bromide. The receptor showed high binding ability for F⁻ and AcO⁻ in acetonitrile.     

Anion recognition by 2,2′-binaphthalene derivatives bearing urea and thiourea groups at 8- and 8′-positions by UV-vis and fluorescence spectroscopies

Synthesis and anion recognition properties of 2,2′-binaphthalene derivatives bearing two thiourea (1) and urea (2) groups at 8- and 8′-positions were studied. The structure of receptor 1 was determined by X-ray crystallography. UV-vis spectra of the receptors showed characteristic changes around 300-400 nm through isosbestic points upon the addition of biologically relevant anions such as acetate, dihydrogenphosphate, and chloride in MeCN and DMSO due to restriction of the rotation around the single bond connecting two naphthyl moieties by cooperative guest binding of two recognition sites. Job’s plots showed 1:1 complexation for guest anions. The fluorescence quantum yields of free form of 1 and 2 in MeCN were determined to be 0.021 and 0.57, respectively. The fluorescence intensities of the receptors diminished upon the addition of anions in MeCN. The association constants of receptors 1 and 2 were one or two orders of magnitude greater than the corresponding monothiourea and urea receptors 3 and 4 indicating cooperative hydrogen bonding with guest anions. The selectivity trends of association of anions were F⁻>AcO⁻>H₂PO₄⁻>Cl⁻>>HSO₄⁻≈NO₃⁻≈Br⁻≈I⁻ for 1, and F⁻>AcO⁻≈Cl⁻>H₂PO₄⁻>Br⁻>HSO₄⁻>I⁻≈NO₃⁻ for 2. Receptor 2 showed remarkable Cl⁻ selectivity presumably owing to suitable orientation for effective hydrogen bond formation with Cl⁻.     

UV-vis and fluorescence spectroscopic detection of anions by the conformational restriction of 2,2′-binaphthalene derivatives bearing thiourea groups through a methylene spacer

Novel fluorescence receptors, 2 and 3 based on 2,2′-binaphthalene possessing thiourea moieties via a methylene spacer have been synthesized. Hydrogen bonds of NH groups of thiourea moieties with acetate anion were confirmed by ¹H NMR study in MeCN-d₃. These receptors showed characteristic UV-vis spectral changes through isosbestic points on complexation with anions inspite of lacking conjugation between the chromophore and the binding sites in polar organic solvent such as acetonitrile. The UV-vis spectral changes arise from the conformational restriction of the 2,2′-binaphthyl skeleton on the complexation. The receptors exhibit high selectivities for AcO⁻ and F⁻. The fluorescence intensity of the receptors decreases with the increasing amount of the AcO⁻, however, addition of F⁻ induces a different change in its fluorescence spectrum, in which shorter emission of the receptors decreases with the increase in F⁻ concentration, while the longer emission of the receptors increases through an isoemissive point in MeCN. The results suggest that favorable dual-wavelength ratiometric fluorescence measurement can be conducted by the receptors for F⁻.     

A new series of potentially hexadentate ligands derived from 2,2′-bipyridine

Reaction of 2,2′-bipyridine-6-carboxaldehyde with the appropriate aliphatic diamine in MeOH and subsequent reduction with NaBH₄ gives the new, potentially hexadentate, ligands N,N′-bis(2,2′-bipyridin-6-ylmethyl)ethane-1,2-diamine (bmet), N,N′-bis(2,2′-bipyridin-6-ylmethyl)propane-1,3-diamine (bmpp) and N,N′-bis(2,2′-bipyridin-6-ylmethyl)hexane-1,6-diamine (bmhx). The syntheses and characterisation of these ligands are reported; the ligands are isolated as the hydrochloride salts, with purification effected by either recrystallisation or cation exchange chromatography. [Co(bmet)](ClO₄)₃ · H₂O is obtained on reaction of bmet · 4.25HCl · 2.5H₂O with Na₃[Co(O₂CO)₃] · 3H₂O, and X-ray structural analysis shows this to have a pair of very short Co–N bonds. The synthesis and characterisation of the first coordination complex containing 6-(aminomethyl)-2,2′-bipyridine (amb) is also described.     

A convenient synthesis of 2,2′-bipyridine derivatives

Picolinates 7 were prepared from the corresponding α-chloro-β-keto-esters 6. Esters 7 were converted into 2,2′-bipyridine derivatives 10 via triazines 9 using an aza Diels-Alder reaction.     

Synthesis and anion binding studies of a new crown ether containing 2,2′-biimidazole

A novel crown ether which incorporates the 2,2′-biimidazole moiety was prepared by cyclization of 1,1′-dibenzyl-1H,1′H-[2,2′]biimidazolyl-4,4′-dicarboxylic acid and 4,7,10-trioxa-1,13-tridecanediamine followed by removal of the benzyl groups. The diacid has been obtained by hydrolysis of the diester previously prepared by alcoholysis of the corresponding dicyano biimidazole. The cyano group is introduced by a palladium-catalyzed procedure starting from the corresponding dibromo biimidazole. The macrocyclic structure of the N-dibenzylated derivative of the receptor has been studied by X-ray diffraction. Binding constants for 1:1 biimidazole–anion complexation (K_assoc) are on the order of 10⁵ M⁻¹ for H₂PO₄⁻ and Cl⁻.     

Application of intramolecular cycloaddition/retro cycloaddition reactions for the synthesis of unsymmetrical 2,2′-bipyridine and 2-benzofuropyrazin-2-ylpyridine analogues

1,2,4-Triazines bearing cycloalkeno[c]pyridine substituents at the 5-position, 2a-d, prepared by an intermolecular Diels-Alder reaction of bi-5,5-triazines with cyclic enamines, were provided with an alkynyloxy or a 2-cyanophenoxy group at the 3-position of the triazinyl unit. A subsequent intramolecular Diels-Alder reaction of the former, followed by loss of N₂ leads to two new classes of 2,2′-bipyridine analogues containing different heterocyclic units, namely cycloalkeno[c]pyridine and 2,3-dihydrofuro- or 2,3-dihydropyrano[2,3-b]pyridine 8a-h; the intramolecular reaction of the 2-cyanophenoxy compound gives benzo[4,5]furo[2,3-b]pyrazine 10a-c.     

Sterically driven electronic properties of naphthalene- and anthracene-end-capped 2,2′-bipyridine luminophores: synthesis and density functional theory

Two naphthalene- and one anthracene-end-capped 4,4′-π-conjugated-2,2′-bipyridine chromophores have been synthesized via the Horner-Wordsworth-Emmons reaction protocol and their electronic absorption and emission properties have been examined. DFT and TD-DFT computational studies have been carried out in order to comprehend the role of steric factor over the electronic factor.     

Synthesis and characterizations of 3,3′-bis(diphenylphosphinoamine)-2,2′-bipyridine and 3,3′-bis(diphenylphosphinite)-2,2′-bipyridine and their chalcogenides

New bis(phosphinoamine) and bis(phosphinite) derivatives of 2,2′-bipyridine were prepared through a single step reaction of 3,3′-diamino-2,2′-bipyridine or 3,3′-dihydroxy-2,2′-bipyridine with diphenylchlorophosphine, respectively. Their P = E chalcogenides (E = O, S, Se) were also prepared. All the new compounds were characterized by elemental analysis, IR and NMR spectroscopies. The molecular structure of 3,3′-bis(diphenylthiophosphinite)-2,2′-bipyridine was elucidated by single-crystal X-ray crystallography.     

Derivatisation of peptides with osmium tetroxide, 2,2′-bipyridine: capillary electrophoretic and MALDI-TOF mass spectrometric study

Site-specific chemical modification is a useful technology in characterisation of proteins, but the number of chemical probes of the protein structure reacting with proteins under mild conditions in aqueous solutions is rather limited. Here we studied the reaction of osmium tetroxide, 2,2′-bipyridine (Os,bipy) with several peptides using capillary zone electrophoresis (CZE) and matrix-assisted laser desorption-ionisation-time-of-flight mass spectrometry (MALDI-TOF MS). Both techniques showed formation of a stable complex of Os,bipy with tryptophan residues. In CZE peaks with different migration times and UV-Vis spectra were observed. MALDI-TOF MS showed the formation of a product with characteristic isotopic pattern corresponding to the presence of osmium atom. Oxidation of cysteine and methionine side chains to cysteic acid and methionine sulfone by Os,bipy was detected by CZE and confirmed by MALDI-TOF and post-source decay (PSD) mass spectra. PSD showed specific shifts of molecular weights of the peptides and their fragments after the derivatisation. We believe that Os,bipy may become a useful agent in the characterisation of proteins.     

S-Transalkylation/ring closing metathesis as a route to azathiamacrocycles incorporating 2,2′-bipyridine subunits

A new route to cyclophanes 6a,b incorporating 2,2′-bipyridine subunits has been elaborated using as the key steps (1) S-transalkylation of 6,6′-bis(methylsulfanyl)-2,2′-bipyridines 2a,b with ethyl bromoacetate resulting in the formation of 6,6′-bis[(ethoxycarbonyl)methylsulfanyl]-2,2′-bipyridines 3a,b and (2) ring-closing metathesis of the corresponding alkenyl ethers 5a,b.     

Sequential homo-coupling Diels-Alder/retro Diels-Alder reaction of 5,5′-bi-1,2,4-triazine-containing thiamacrocycles as a new route to thiacrown ethers incorporating a 2,2′-bipyridine subunit

A new route to thiacrown ethers 5a-d and 6a-d incorporating a 2,2′-bipyridine subunit is elaborated using, (1) homo-coupling of 1,2,4-triazine sulfides 3a-d tethered to poly(ethylene glycol) chains with potassium cyanide and (2) Diels-Alder/retro Diels-Alder reaction with norbornadiene or 1-pyrrolidino-1-cyclopentene as the key steps.     

A convenient synthesis of pyridine and 2,2′-bipyridine derivatives

α-Chloro-α-acetoxy-β-keto-esters 9 were readily prepared from β-keto-esters 6 in good overall yields. These compounds reacted as α,β-diketo-ester equivalents 2 with amidrazones 1 yielding triazines 3, generally in good yields. Picolinates 10 provided an alternative source of α,β-diketo-ester equivalents 2 when treated with copper(II) acetate. A ‘one-pot’ reaction of the α,β-diketo-ester equivalents 2 with amidrazones 1 in the presence of 2,5-norbornadiene 5 in boiling ethanol yielded the pyridines 4 and 2,2′-bipyridines 4 (R¹=2-pyridyl) directly without the need to isolate the corresponding triazines 3. Triazine 3c reacted with the aza-dienophiles 13 and 17 affording the products 16 and 18, respectively, in good yields.     

A novel approach to conformationally strained 2,2′-bipyridine thiacrown ethers and their chiral sulfoxides by sequential homo-coupling/DA-rDA reaction of 5,5′-bi-1,2,4-triazine-containing thiamacrocycles

The synthesis of conformationally strained 2,2′-bipyridine thiamacrocycles 5, 6, 9, 10 and their chiral sulfoxides 11-14 is elaborated using, (1) homo-coupling of 1,2,4-triazine sulfide 3 with potassium cyanide and (2) Diels-Alder/retro Diels-Alder (DA-rDA) with 2,5-norbornadiene or 1-pyrrolidino-1-cyclopentene as the key steps. The crystal structure determinations of 4-6 and the theoretical calculations at DFT/B3LYP/6-311G^∗∗ level were conducted thus establishing conformational preferences of the target thiamacrocycles     

A facile S-transalkylation of 2,2′-bipyridine alkyl sulfides—a new tool for the synthesis of annulated biheterocycles

A simple and efficient synthesis of annulated 2,2′-bipyridinium salts with attached dihydrothiazole or dihydro-1,3-thiazine rings has been developed through tandem S-transalkylation/intramolecular ring closure of 2,2′-bipyridine alkyl sulfides. The structures were confirmed by X-ray crystallographic analysis.     

Barium ion sensing by a 2,2′-binaphthalene derivative bearing two monoaza-15-crown-5 ethers

A novel fluoroionophore 1 based on 2,2′-binaphthalene bearing two monoaza-15-crown-5 ethers at 8- and 8′-positions was prepared. UV-vis and fluorescence responses of 1 upon the addition of alkali and alkaline earth metal cations were evaluated in 15% MeOH-MeCN. Receptor 1 showed unique response for Ba²⁺ due to the formation of an intramolecular sandwich complex.     

Synthesis and properties of 4,4′-bipyridine based tetracationic carbazolophanes

The precyclophane derived from 3,6-bis(bromomethyl)-9-ethylcarbazole and 5 equiv of 4,4′-bipyridine underwent macrocyclization on quaternization with various dibromides including 3,6-bis(bromomethyl)-9-ethylcarbazole to give carbazole-paraquat, self-complementary, cyclophanes revealing distinct charge-transfer and electrostatic interactions. The macrocyclic carbazolophane 1 was also obtained by a one-pot quaternization technique using equimolar amounts of 3,6-bis(bromomethyl)-9-ethylcarbazole and 4,4′-bipyridine.     

A simple one-pot synthesis of functionalised 6-(indol-3-yl)-2,2′-bipyridine derivatives via multi-component reaction under neat condition

A series of 4-aryl-6-(1H-indol-3-yl)-2,2-bipyridine-5-carbonitrile derivatives were synthesized via a one-pot multi-component reaction of aromatic aldehydes, 3-(cyanoacetyl)indole and 2-acetyl pyridine in ammonium acetate by conventional heating and microwave irradiation under solvent-free condition. Also a series of 6,6′-di(1H-indol-3-yl)-4,4′-diaryl-2,2′-bipyridine-5,5′-dicarbonitrile derivatives were synthesized using cinnamils, 3-(cyanoacetyl)indole and ammonium acetate. The methodology affords high yields of product at short reaction time.     

Spectroscopic, thermal and structural studies of cocrystal of 2,2′-diamino-4,4′-bis(1,3-thiazole) with 4,4′-bipyridine, 1,2-bis(4-pyridyl)ethylene and 1,3-bis(4-pyridyl)propane

Three new cocrystals based upon 2,2′-diamino-4,4′-bis(1,3-thiazole) (DABTZ) with 4,4′-bipyridine (4,4′-bipy), 1,2-bis(4-pyridyl)ethylene (bpe) and 1,3-bis(4-pyridyl)propane (bpp): [(DABTZ) (4,4′-bipy)], [(DABTZ) (bpe)] and [(DABTZ) (bpp)] have been synthesized and characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR spectroscopy and studied by thermal and X-ray crystallography. Self-assembly of these compounds in the solid state is likely caused by both hydrogen bonding, and π-π stacking.