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.     

Investigation on the thermal degradation of acrylic polymers with fluorinated side-chains

The thermal degradation of poly-2,2′,3,3′,4,4′,5,5′,6,6′,7,7′,7″-tridecafluoroheptylacrylate and poly-2,2′,3,3′,4,4′,5,5′,6,6′,7,7′-dodecafluoroheptylmethacrylate has been studied in isothermal conditions at 450-750 °C using pyrolysis-gas chromatography. The type and composition of the pyrolysis products give useful information about mechanism of thermal degradation. It was shown that the main thermal degradation process for both polymers is random main-chain scission. The major degradation products for fluorinated polyacrylate are monomer, dimer, saturated diester, trimer, and corresponding methacrylate. The fluorinated polymethacrylate gives monomer as the main product of thermal destruction. As a result of side-chain reaction, the thermal degradation of the fluorinated polyacrylate also produces remarkable amounts of alcohol. On the other hand, the respective alcohol is only a minor component among the pyrolysis products of the fluorinated polymethacrylate. For both polymers, the main nontrivial degradation product coming from the alkyl ester decomposition is the corresponding fluorinated cyclohexane. The formation of the fluorinated cyclohexanes may be accounted for a nucleophilic bimolecular substitution pathway.     

One-pot synthesis of 5,5′-dibromo-2,2′-dipyridylacetylene and its boronic acid derivative

5,5′-Dibromo-2,2′-dipyridylacetylene was prepared from 2,5-dibromopyridine and (trimethylsilyl)acetylene via the new one-pot synthesis approach using a regioselective palladium-catalyzed coupling reaction with a 60% yield. Several protocols of lithium-halogen exchange were then attempted to synthesize 6,6′-(1,2-ethynediyl)bis[3-pyridylboronic acid] from 5,5′-dibromo-2,2′-dipyridylacetylene. The former was successfully obtained with a 54% yield by a reverse addition method using toluene and THF and it showed potential as a useful building block for cross-coupling reactions in the formation of carbon-carbon bonds.     

Facile acid-catalyzed condensation of 2-hydroxy-2,2′-biindan-1,1′,3,3′-tetrone with phenols, methoxyaromatic systems and enols

Various phenols, methoxy aromatic compounds, 3- and 4-hydroxycoumarins and enols smoothly condense with 2-hydroxy-2,2′-biindan-1,1′,3,3′-tetrone 1 in an acid medium producing 2-aryl/alkyl-2,2′-biindan-1,1′,3,3′-tetrones in high yields. The adducts of resorcinol, 1,3,5-trihydroxybenzene and α- and β-naphthols of 1 preferably remain in the intramolecular hemi-ketal form, confirmed by X-ray diffraction studies. On the other hand para and meta substituted phenols condense with 1 in an acid medium to produce 6 or 7 substituted 2′,4-spiro(1′,3′-indanedion)-indeno[3,2-b]chromenes in good yields.     

Efficient bimetallic titanium catalyst for carbonyl-ene reaction

A new family of achiral 3,3′,5,5′-tetrasubstituted-2,2′,6,6′-tetrahydroxy biphenyl ligand 4 was developed. The axial chirality of the ligand could be induced by the chelation of 2,2′,6,6′-tetrahydroxy groups with (R)-BINOL-Ti(OⁱPr)₂ to form an axially chiral bimetallic titanium catalyst 9. Compared with (R)-BINOL-Ti(OⁱPr)₂ catalyst, this novel catalyst 9 exhibited excellent activity and enantioselectivity for the carbonyl-ene reaction of methylstyrene and ethyl glyoxylate. 3,3′,5,5′-Tetrasubstituted groups showed a remarkable effect on both enantioselectivity and yield. With 9d prepared from 3,3′,5,5′-tetramethyl-2,2′,6,6′-tetrahydroxy biphenyl 4d as the catalyst, the best result, up to 97.6% ee and 99% yield, was obtained. Additionally, the bimetallic catalyst 9 also showed better catalytic capability than the corresponding monometallic catalyst.     

The highly regiospecific synthesis and crystal structure determination of 1,1′-2,5′ substituted ring-locked ferrocenes

1,1′-Ferrocene biscarboxaldehyde (1) has been prepared and the aldehyde groups were subsequently protected with acetal groups to produce 1,1′-bisacetalferrocene (2). A ring-locked ferrocene was synthesised by further derivatisation of the cyclopentadiene rings at the 2,2′ positions with phosphine substituents to produce 2,2′-bis-(acetal)-1,1′-diphenylphosphinoferrocene (3), which was subsequently coordinated to either a nickel chloride (5) or nickel bromide (6) metal centre. The ring-locked ferrocene complexes produced 2,5′-bis-(acetal)-1,1′-diphenylphosphinoferrocene substitution patterns. The acetal protecting groups of 2,2′-bis-(acetal)-1,1′-diphenylphosphinoferrocene were removed to produce 1,1′-bis-carboxaldehyde-2,2′-diphenylphosphinoferrocene (4). The Cp rings of 1,1′-bisacetalferrocene were also further derivatised at the 2,2′ positions with a silane to produce the ring-locked 1,1′-siloxane-2,5′-bisacetalferrocenophane (7). The acetal protecting groups were removed from this to produce 1,1′-siloxane-2,5′-ferrocenophanecarboxaldehyde (8). For both the phosphine and siloxane electrophiles, the substitution on the Cp rings gives chiral products (obtained as racemic mixtures). Due to the highly regioselective nature of the reaction and diastereoselectivity in the products only C₂-symmetric compounds were observed without the presence of meso diastereoisomers. Subsequent ring-locking forced the Cp rings to rotate, leading to 1,1′-ring-locked ferrocenes with 2,5′-arrangement of the acetal groups (i.e. on opposite faces of the ferrocene unit).     

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.     

New optically active organoantimony (BINASb) and bismuth (BINABi) compounds comprising a 1,1′-binaphthyl core: synthesis and their use in transition metal-catalyzed asymmetric hydrosilylation of ketones

Racemic 2,2′-bis[diarylstibano]-1,1′-binaphthyls [(±)-BINASbs] and 2,2′-bis[di(p-tolyl)bismuthano]-1,1′-binaphthyl [(±)-BINABi], which are the antimony and bismuth congeners of BINAP, have been prepared from 2,2′-dibromo-1,1′-binaphthyl (DBBN) via 2,2′-dilithio-1,1′-binaphthyl intermediate by treatment with the appropriate metal halides [(p-Tol)₂SbBr, Ph₂SbBr and (p-Tol)₂BiCl]. The optical resolution of the (±)-BINASbs could be achieved via the separation of a mixture of the diastereomeric Pd-complexes derived from the reaction of (±)-BINASbs with di-μ-chlorobis{(S)-2-[1-(dimethylamino)-ethyl]phenyl-C¹,N}dipalladium(II). Optically active (R)-BINASb and (R)-BINABi could be also obtained from optically active (R)-DBBN by the same procedure. The enantiopure BINASbs have been shown to be effective chiral ligands for the rhodium-catalyzed asymmetric hydrosilylation of ketones.     

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.     

A simple synthetic approach to homochiral 6- and 6′-substituted 1,1′-binaphthyl derivatives

Various homochiral binaphthyl derivatives having functional groups at the 6-position are important key intermediates for the immobilization of binaphthyl compounds on various solid-supports and have been prepared from commercially available 1,1′-bi-2-naphthol via controlled monopivalation of the 2-hydroxyl group and electrophilic aromatic substitution at the 6-position. (S)-2,2′-Bis-((S)-4-alkyloxazol-2-yl)-6-(2-methoxycarbonyl)ethyl-1,1′-binaphthyls (6-functionalized (S,S)-boxax)) were prepared and immobilized on various polymer supports including PS-PEG, PS, PEGA and MeO-PEG resin.     

On the oxidative coupling of N,N-disubstituted 2-aminothiophenes—synthesis of N,N′-persubstituted 5,5′-diamino-2,2′-bithiophenes

The oxidative coupling of N,N-disubstituted 2-aminothiophenes performed by several heavy-metal free oxidizing agents gives rise to the formation of N,N′-persubstituted 5,5′-diamino-2,2′-bithiophenes which are of interest as hole-transport materials for optoelectronic applications.     

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.     

Development of metal complex imprinted solid-phase microextraction fiber for 2,2'-dipyridine recognition in aqueous medium

In this paper, a novel metal complex imprinted polymer (CIP) coated solid-phase microextraction (SPME) fiber was prepared which could recognize the complex template [Cu(OAc)₂(2,2′-dipyridine)] in aqueous medium. The saturating adsorption capacity of CIP-coated fiber was 2.2 and 2.6 times greater than those of molecularly imprinted polymer (MIP) coated fiber and nonimprinted polymer (NIP) coated fiber, respectively. Extraction conditions that influenced the recognition performance of CIP-coated fiber were investigated including pH, extraction solvent, metal ion species, etc. The ligand selectivity was also evaluated and discussed. The results demonstrated that CIP-coated fiber had better binding affinity for 2,2′-dipyridine compared to its structure analogues. The recognition ability of CIP coating was stable and effective in aqueous medium while MIP coating showed weak imprinting effect due to disturbance from protic solvent. 2,2′-dipyridine extracted by CIP-coated fiber using HPLC/UV detection resulted in a linear range of 10-200 μg/L with a detection limit of 2.0 μg/L. The proposed method was successfully applied to the analysis of 2,2′-dipyridine in spiked tap water, laboratory wastewater and human urine samples with recoveries 80.3-103.3% and RSDs 5.5-8.9%.     

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.     

Facile synthesis of 6-iodo-2,2′-dipivaloyloxy-1,1′-binaphthyl, a key intermediate of high reactivity for selective palladium-catalyzed monofunctionalization of the 1,1′-binaphthalene core

A high-yielding procedure for selective monoiodination of 2,2′-dihydroxy-1,1′-binaphthyl (BINOL) is reported. 6-Iodo-2,2′-dipivaloyloxy-1,1′-binaphthyl, obtained in three steps starting from BINOL in 88% overall yield, proved to be a highly efficient substrate in various palladium-catalyzed coupling (Stille, Heck, Sonogashira, and Suzuki coupling) and carbonylation reactions compared to the analogous 6-bromo derivative.     

A simple and environmentally benign synthesis of polypyridine-polycarboxylic acids

An oxidation method using dilute nitric acid solutions under solvothermal conditions has been developed to synthesise a series of polypyridine-polycarboxylic acids. It has been successfully applied to a range of methyl substituted polypyridines including symmetrical and asymmetrical 2,2′-bipyridines; 2,2′:6′,2″-terpyridines and; 2,2′:6′,2″:6″,2?-tetra-pyridines and yields crystalline polypyridine-polycarboxylic acids in a single step. Simple product recovery through filtration yields a recyclable filtrate. More forcing conditions led to demethylation of the polypyridine ligand most probably via decarboxylation. This simple approach avoids potentially harmful metal-based oxidants and negates any issues associated with the disposal of their resultant (hazardous) waste.     

The relevance of the fluorine interactions in the supramolecular structure of a complex constructed from copper(II) hexafluoroacetylacetonate and the 4′-(3-pyridyl)-2,2′:6′,2″-terpyridine ligand. Novel C-F/π synthons involving the π-system of the terpyridine moieties and those of the hexafluoroacetylacetonate chelate rings

Reaction of 4′-(3-pyridyl)-2,2′:6′,2′′-terpyridine (pyterpy) with Cu(hfacac)₂ (hfacac = hexafluoroacetylacetonate) led to the formation of the novel compound [Cu₃(hfacac)₄(μ-pyterpy)₂][Cu(hfacac)₃]₂ (1). The structure is composed of a trinuclear [Cu₃(hfacac)₄(μ-pyterpy)₂]²⁺ cation and two [Cu(hfacac)₃]⁻ anionic species. The cation consists of a chain of three Cu^II atoms connected by bridging pyterpy ligands. The [Cu(hfacac)₃]⁻ anions have the hfacac ligands coordinated in their usual chelating manner through their carbonyl O donors. Besides the coulombian forces, the ionic species are fixed by C-H?O, C-H?F, F?F and a variety of unusual inter-ion C-F?π interactions that control the packing motif. These π-interactions involve the terpyridine groups from the pyterpy ligand and the five-membered rings of the chelating hexafluoroacetylacetonate anions.     

Synthesis of new fluorescent 2-(2′,2″-bithienyl)-1,3-benzothiazoles

Bithienyl-1,3-benzothiazole derivatives were synthesised by reacting various 5-formyl-5′-alkoxy- or 5-formyl-5′-N,N-dialkylamino-2,2′-bithiophenes with ortho-aminobenzenethiol in good to excellent yields. Evaluation of the fluorescence properties of these compounds was carried out. They show strong fluorescence in the 450-600 nm region, as well as high quantum yields and large Stokes’ shifts.     

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.     

A simple synthesis of 2,2′-bipyrroles from pyrrole

2,2′-Bipyrroles, which are obvious precursors for the synthesis of 2,2′-bipyrrole-based natural products, are synthesized in three steps from pyrrole employing known pyrrolyl ketoalcohols by a sequential alcohol oxidation and Paal-Knorr pyrrole synthesis.