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The gas phase pyridine synthesis process is usually carried out in a fluidized bed reactor. The contact efficiency between the reactants and the catalysts has great influence on the reactor performance. In this paper, three fluidized bed reactors with different flow patterns were used to investigate the contact efficiency. The superficial contact efficiency index (SCEI) was defined and used in this paper to quantify the contact efficiency inside these reactors. To obtain the values of the SCEI, the ideal reactor model was constructed. The results showed that the SCEI average value decreased as the flow pattern shifted from fast fluidization to bubbling fluidization; these values were 0.86, 0.55, and 0.19 for the fast fluidized bed reactor, turbulent fluidized bed reactor, and bubbling fluidized bed reactor, respectively. An empirical correlation was proposed in this paper to predict the SCEI under different operating conditions. The model prediction results agreed well with experimental results with an average prediction error of 8%. [ABSTRACT FROM AUTHOR]

A Co‐catalyzed enantioselective desymmetric [2+2+2] cycloaddition for synthesis of pyridines with all‐carbon quaternary carbon centers has been developed. The regio‐ and enantioselectivities are controlled by the inherent nature of terminal alkynes and the substituents on the bisoxazolinephosphine ligands. Pyridines with 5‐substitutents could be obtained with >20:1 regioselectivity and up to 94 % ee when terminal alkyl, alkenyl or silyl alkynes and DTBM/Ph‐based NPN* ligand L6 were used. Terminal aryl alkynes and Ph/Bn‐based ligand L4 leads to formation of pyridines with 6‐substitutents in up to 99 % ee. [ABSTRACT FROM AUTHOR]

N‐heterocyclic carbene‐catalyzed activation of ynals for rapid synthesis of pyridine derivatives with important utilities has been reported. This successful strategy using NHC‐bound alkynyl acyl azolium as the key intermediate further improved the application of N‐Ts 2‐aminoacrylate as a nucleophile. Importantly, this work introduces an ester substituent to pyridines that could be easily transformed to other functional groups. [ABSTRACT FROM AUTHOR]

We synthesised palladium and platinum complexes possessing cyclic and acyclic pincer‐type polyaromatic ligands and investigated their structural effect on the catalysis. The pincer‐type bis(6‐arylpyridin‐2‐yl)benzene skeleton was constructed via Kröhnke pyridine synthesis under transition metal‐free conditions on gram‐scale quantity. Ligand structure significantly influenced catalytic activity toward the platinum‐catalysed hydrosilylation of diphenyl acetylenes, despite the ligand‐independence of the conformations and electronic properties of these complexes. [ABSTRACT FROM AUTHOR]

The catalytic effects of two forms of nano‐TiO2, which are prepared via an ordinary or a magnetized process, are investigated in the synthesis of pyridine dicarbonitriles by one‐pot multicomponent reaction of 4‐methyl thiophenol, malononitrile, and aryl aldehydes. The results have shown that both prepared nano‐TiO2 exhibited high catalytic activities toward the synthesis of pyridine dicarbonitrile derivatives but the nano‐TiO2, which is prepared via a magnetized process, has shown better catalytic activity. Furthermore, this new catalytic method for the synthesis of pyridine dicarbonitriles provides rapid access to the desired compounds in high yields and so a simple work‐up procedure in the presence of water at room temperature. Therefore, this method represents a significant improvement incompatible of the other methods that are available for the synthesis of pyridine dicarbonitriles. [ABSTRACT FROM AUTHOR]

A convenient and efficient strategy has been devised for the synthesis of bipyrido‐fused coumarins employing Kröhnke's pyridine synthesis approach. In the present work, 4‐hydroxycoumarins 1a–d were reacted with appropriate chalcones 2a–c to afford desired bipyridyl‐fused coumarins 3a–l. The structures of all the newly synthesized compounds 3a–l were ascertained by IR, 1H NMR, 13C NMR, mass spectral data, and elemental analyses. The compounds were further evaluated for their antimicrobial response against representative panel of pathogens, and the results thus obtained were compared with those of standard drugs. Few of the derivatives 3c, 3f, and 3i exhibited promising potency. [ABSTRACT FROM AUTHOR]

An efficient copper‐catalyzed cyclization of acetophenone and ammonium acetate with release of methane has been developed for the synthesis of polysubstituted pyridines. A series of 2,4,6‐triphenyl‐pyridines has been produced in good yields. This synthetic method is sustainable, simple, and environment‐friendly. [ABSTRACT FROM AUTHOR]

A facile approach to access polysubstituted pyridine derivatives starting from Baylis‐Hillman adducts is disclosed. The reactions proceeded smoothly by sequential AlCl3‐catalyzed condensation/aza‐Wittig/isomerization reactions, leading to the target products at room temperature within 24 h in moderate to good yields. Furthermore, the final products were evaluated in mycelial growth tests against Pythium dissimile, Botryotinia fuckeliana and Zymoseptoria tritici and showed potential activities. [ABSTRACT FROM AUTHOR]

2,2′‐Bipyridyls have been utilized as indispensable ligands in metal‐catalyzed reactions. The most streamlined approach for the synthesis of 2,2′‐bipyridyls is the dehydrogenative dimerization of unfunctionalized pyridine. Herein, we report on the palladium‐catalyzed dehydrogenative synthesis of 2,2′‐bipyridyl derivatives. The Pd catalysis effectively works with an AgI salt as the oxidant in the presence of pivalic acid. A variety of pyridines regioselectively react at the C2‐positions. This dimerization method is applicable for challenging substrates such as sterically hindered 3‐substituted pyridines, where the pyridines regioselectively react at the C2‐position. This reaction enables the concise synthesis of twisted 3,3′‐disubstituted‐2,2′‐bipyridyls as an underdeveloped class of ligands. [ABSTRACT FROM AUTHOR]

In this work, a calixarene based ionic liquid was successfully prepared and characterized by different techniques. This ionic liquid was used as an efficient catalyst for the synthesis of a series of polysubstituted pyridines from aldehydes, malononitrile, 1,3‐diketones and arylamines in water as a green solvent. Also, for the first time, symmetric and unsymmetric polysubstituted bis‐pyridines were obtained in high yields from diamines using this catalyst. Mild reaction conditions, high to excellent yields, easy work‐up, excellent activity and reusability of the catalyst are the key features of this method which make it an interesting and novel alternative for the synthesis of the above mentioned important heterocyclic compounds. [ABSTRACT FROM AUTHOR]

A highly efficient and flexible protocol for intramolecular annulation of exocyclic β‐enaminones has been disclosed for the synthesis of carbazolones and imidazo[1,2‐a]pyridines through a counter‐anion‐controlled free‐radical mechanism promoted by hypervalent iodine(III). The cooperative behavior of HTIB and AgSbF6 plays a crucial role in the intramolecular annulation process through C−C and C−N bond formation to give the desired products. The mechanistic insights suggest that the two competitive reactions involved in the system are guided by the nature of the counteranion, which determines the formation of the final products. A wide variety of carbazolones and imidazo[1,2‐a]pyridine molecules have been prepared and isolated in good to excellent yields. [ABSTRACT FROM AUTHOR]

A palladium‐catalyzed coupling between aryl halides and monocyclopropanated pyrroles or furans has been developed, leading to valuable six‐membered N‐ and O‐heterocycles. As the key step, a selective cleavage of the non‐activated endocyclic C−C bond of the 2‐heterobicyclo‐[3.1.0]hexane framework is achieved. The developed method offers access to highly functionalized piperidines, pyridines, and pyrans that are challenging to access by traditional methods. Heck‐type arylation of cyclopropanated furans and pyrroles proceeds with ring expansion via the unactivated cyclopropyl bond, giving rise to arylated diyhdropyridines, pyridines, and 2H‐pyrans. [ABSTRACT FROM AUTHOR]

With the aim of discovering a lead compound for pyridine‐based fungicide bearing adamantane moiety, a series of novel O‐alkyl/benzyl‐1‐(adamantan‐1‐yl)‐2‐(pyridin‐3‐yl)ethan‐1‐one oximes were synthesized from 3‐methylpyridine, ethyl (adamantan‐1‐yl)carboxylate, and alkoxyamine or benzoxyamine hydrochloride. The in vitro antifungal activity against four pathogenic fungi was evaluated, and some compounds exhibited good antifungal activity. Compounds 3d and 3f demonstrated strong activity against Sclerotinia sclerotiorum, with EC50 values of 11.25 and 12.87 μg/mL, respectively; 3b, 3c, and 3k had notable activity against Botrytis cinerea, with EC50 values of 12.78, 12.57, and 11.97 μg/mL, respectively. For Rhizoctonia Solani, 3d and 3g showed sufficient activity with EC50 values of 9.66 and 8.90 μg/mL, respectively. In addition, 3d and 3g demonstrated moderate activity against Colletotrichum orbiculare, with EC50 values of 14.32 and 15.83 μg/mL, respectively. A series of novel O‐alkyl/benzyl‐1‐(adamantan‐1‐yl)‐2‐(pyridin‐3‐yl)ethan‐1‐one oximes were synthesized, and their in vitro antifungal activities against four pathogenic fungi were evaluated. Compounds 3d and 3f possessed strong activity against Sclerotinia sclerotiorum; and 3b, 3c, and 3k had notable activity against Botrytis cinerea. For Rhizoctonia Solani, 3d and 3g showed sufficient activity. [ABSTRACT FROM AUTHOR]

Facile and efficient protocols for the synthesis of 2‐R‐6,8‐dinitro[1,2,4]triazolo[1,5‐a]pyridines from commercially available starting materials have been developed. The reactions proceed via cyclization of corresponding 3,5‐dinitropyridine‐2‐yl hydrazides or aldehyde 3,5‐dinitropyridine‐2‐yl hydrazones followed by in situ Dimroth rearrangement to provide these triazole fused bicyclic heterocycles in good yields under mild conditions. Another synthetic route to target N‐bridged dinitro[1,2,4]triazolo[1,5‐a]pyridines includes arylation of 5‐aryltetrazoles with 2‐chloro‐3,5‐dinitropyridine and subsequent thermal decomposition/cyclization. A series of 6,8‐dinitro[1,2,4]triazolo[1,5‐a]pyridines with variety of substituents in position 2 have been synthesized from readily available starting materials. General methods include acid‐catalysed cyclization of 3,5‐dinitropyridine‐2‐yl hydrazides and oxidation of aldehyde 3,5‐dinitropyridine‐2‐yl hydrazones to give mentioned dinitro compounds in moderate to excellent yields. [ABSTRACT FROM AUTHOR]

A general and efficient protocol was developed for the synthesis of polysubstituted pyridines from propargyl amines and unsaturated carbonyl compounds through a tandem condensation/alkyne isomerization/6π 3‐azatriene electrocyclization sequence. This process was found to be applicable to a wide range of readily available substrates (30 examples, up to 95 % yield) and could be readily performed on a preparative (20 g) scale. By taking advantage of this method for late‐stage pyridine incorporation, we successfully completed the collective total synthesis of suveoline, norsuveoline, and macrophylline. [ABSTRACT FROM AUTHOR]

The design and synthesis of homochiral double helicates are reported that are constructed by means of Ag‐induced supramolecular self‐sorting of saddle‐shaped cyclooctatetrathiophene‐based pyridine ligands (1 and 2). The intramolecular S⋅⋅⋅N interaction ensures that the thiophene and pyridine rings of ligands 1 and 2 are in coplanar and syn‐locked structures. In the presence of Ag+, the racemic ligands 1 and 2 only afforded homochiral double helicates, indicating effective chiral self‐sorting process under the influence of the S⋅⋅⋅N interaction. The X‐ray crystal structure of 12Ag2 reveals a pair of homochiral double helicates (R,R,R,R)‐12Ag2 and (S,S,S,S)‐12Ag2. Furthermore, chiral resolution of racemic ligand 1 was achieved by chiral‐phase HPLC, and the enantiomers and their corresponding enantiopure Ag complexes were characterized. Asyn‐locked strategy for the design of homochiral double helicates, (R,R,R,R)‐12Ag2 and (S,S,S,S)‐12Ag2, is presented based on chiral self‐sorting by utilizing the intramolecular S⋅⋅⋅N interactions, from chiral saddle‐shaped cyclooctatetrathiophene bearing pyridine groups [(R,R)‐1 and (S,S,)‐1]. [ABSTRACT FROM AUTHOR]

A systematic study of the synthesis and properties of 1‐aza‐, 4‐aza‐, and 1,4‐diaza[4]helicenes as well as the previously unknown S‐shaped double 1,4‐diaza[4]helicenes has been reported. The synthetic route to the aza‐ and diaza[4]helicenes involved an electrophile‐induced cyclization of 3(2)‐alkynyl‐2(3)‐(naphthalen‐1‐yl)azines (i.e., quinoxaline, pyrazine, pyridine), which were prepared in two steps from the commercially available ortho‐dihalo‐substituted azine. Trifluoroacetic acid (TFA) and ICl were used as electrophiles. The ICl‐promoted cyclization provided the 5‐iodo derivatives of the aza‐ and diaza[4]helicenes in yields of 47–71 %. The use of TFA as the electrophile afforded the helicenes along with isomeric products from an alternative cyclization and subsequent 1,2‐shift of the C–C bond (e.g., naphtho[2,1‐f]quinoxalines or naphtho[2,1‐a]phenazines, 87–89 % total yield, 1.5–1.8:1 ratio). The presence of an iodine substituent in the hetero[4]helicenes allowed for the introduction of an alkynyl group by using a Sonogashira reaction. The subsequent cycloizomerization upon treatment with TFA gave the S‐shaped double 1,4‐diaza[4]helicenes. The molecular structures and crystal packing of the synthesized hetero[4]helicenes relative to those of [4]carbohelicene have been discussed. [ABSTRACT FROM AUTHOR]

A new class of 2,6‐pyridine linked bis (oxadiazoles), bis (thiadiazoles), and bis (triazoles) were prepared from the synthetic intermediates pyridine‐2,6‐dicarbohydrazide, E‐aroylethenesulfonylacetic acid and E‐arylsulfonylethenesulfonylacetic acid adopting ultrasonication methodology and tested for their antioxidant activity. Among all the tested compounds 2,6‐(bis (2‐(4‐methylbenzoylethenesulfonylmethyl)‐1,3,4‐oxadiazol‐5‐yl))‐pyridine (7b) was found to be potential antioxidant agent. [ABSTRACT FROM AUTHOR]

Abstract: Abundant and inexpensive iron, readily catalyzed the oxidative tandem reactions of arylalkylketones and benzylamines using molecular oxygen as the green oxidant in one‐pot solvent‐free conditions. 2,4,6‐Triaryl pyridines containing a wide variety of functional groups are synthesized from easily available starting materials. The synthetic importance of this reaction protocol has been demonstrated by preparing topoisomerase I and II inhibitors, and other valuable pyridine derivatives. Key intermediates are isolated and a plausible mechanism has been proposed. [ABSTRACT FROM AUTHOR]

Abstract: A metal‐free one‐pot strategy has been developed for the synthesis of 3‐aryl[1,2,4]triazolo[4,3‐a]pyridines through an oxidative cyclization of 2‐(2‐arylidenehydrazinyl)pyridines by utilizing molecular iodine in DMSO. This is the first report on the synthesis of 3‐aroyl[1,2,4]triazolo[4,3‐a]pyridines directly from α‐aryl methyl ketones or ethyl benzoylacetate or styrenes or phenylacetylenes and 2‐hydrazinylpyridines via iodine promoted oxidative cyclization. The catalytic use of iodine makes this method quite simple, more convenient and economical. Moreover, this protocol showed broad substrate scope under mild reaction conditions and could override the usage of hazardous metal reagents. [ABSTRACT FROM AUTHOR]

N‐2‐amino‐4‐(furan‐2‐yl)‐5,6‐dimethylnicotinonitrile (4) was utilized as key intermediate for the synthesis of some new, pyridopyrimidine, benzo[1,5][g]oxazocine, naphthoquinone, and isoindole derivatives. The structures of the newly synthesized compounds were confirmed by elemental analysis, IR, 1H‐NMR, and mass spectral data. [ABSTRACT FROM AUTHOR]

Abstract: A new approach to generate 2,4,6‐trisubstituted pyridines was successfully developed based on the cyclization of α,β‐unsaturated oximes catalyzed by copper(I). The method takes advantage of the inherent properties of α,β‐unsaturated oximes to generate pyridines. In this transformation, α,β‐unsaturated oximes play dual roles in the formation of nucleophilic copper(II) enamide and as the acceptor in the Michael addition. [ABSTRACT FROM AUTHOR]

Abstract: A new method for the synthesis of imidazo[1,5‐α]pyridines, one of the most important N‐heterocyclic compounds due to their wide application, was reported in this study. Specifically, using I2 as a non‐metal catalyst and TBPB as an oxidant can efficiently facilitate the synthesis and avoid the use of a metal catalyst. The reaction between ethyl (E)‐2‐(benzylideneamino)acetate and pyridine represents an unprecedented 1,3‐diolar cycloaddition in highly straightforward process with great value. [ABSTRACT FROM AUTHOR]

Abstract: Substituted 1H‐1,2,3‐triazol‐4‐yl‐pyrrolo[2,3‐b]pyridines are efficiently prepared by a one‐pot coupling/cyclization/desilylation Cu alkyne/azide cycloaddition (CuAAC) sequence in the sense of a consecutive three‐component fashion. The key feature of this new de novo formation of azole and triazole anellation is the sequentially Pd/Cu‐catalyzed process employing tri(iso‐propyl)silyl (TIPS) butadiyne as a four‐carbon building block. In addition, the sequence can be expanded in a four‐component fashion also employing the in situ formation of the required azides. [ABSTRACT FROM AUTHOR]

Tetrahydropyridines are important heterocycles present in many molecules of natural and non‐natural origins that exhibit a wide array of biological activities. With several sp3‐hybridized carbon atoms in their structure, they often include one or several stereogenic centers, whose control represents a great synthetic challenge. For the past two decades, enantioselective organocatalysis has developed as a very powerful strategy to perform the synthesis of enantioenriched compounds, including heterocycles. In this Microreview, we wish to provide the readers with a general overview about the organocatalytic strategies that have been used to achieve the preparation of diversified families of tetrahydropyridines, thereby providing elements of reflection for further developments. [ABSTRACT FROM AUTHOR]

Abstract: Cu‐catalyzed redox‐divergent [3+3] coupling of oxime esters with β‐CF3 enones and acrylates is described. This redox‐neutral coupling with enones and acrylates affords trifluoromethylated pyridines and pyridones, respectively. Under reductive conditions, difluoromethylated pyridines, difluoromethlated pyridones, and trifluoromethylated dihydropyridones are obtained. The reactions occur under mild conditions with broad substrate scope and regio/redox selectivity. [ABSTRACT FROM AUTHOR]

A series of photoswitchable precursors based on [Fe(NCX)2L(L′)2], where X = S or Se, L is a bidentate ligand (phenanthroline or bipyrimidine), and L′ a monodentate ligand such as a pyridine or picoline derivative, were synthesized and their spin crossover (SCO) properties investigated in detail. The thermal and light‐induced magnetic properties of a family of [Fe(NCS)2L(py)2] [py = pyridine and L = bipyrimidine (1) or phenanthroline (phen) (2)] is reported. The [Fe(NCX)2(phen)(L′)2] compounds were further explored by changing the counteranion from NCS– to NCSe– (3) or by replacing pyridine with 4‐picoline (4) or 4‐ethylpyridine (5). Complexes 1–4 exhibit thermal and light‐induced SCO, while 5 remains in the high‐spin state. The kinetics governing the photoinduced back‐conversion was investigated for compounds 2 and 4. Complex 2 exhibits LIESST relaxation kinetics involving strongly cooperative (sigmoidal) behavior, whereas complex 4 displays a stretched exponential shape, typical for broad distributions of relaxation times. These results are discussed on the basis of the steric hindrance due to bulkiness and the electronic influence of the substituent effects on the magnetic and photomagnetic properties of mononuclear iron(II) complexes. [ABSTRACT FROM AUTHOR]

Abstract: The benzylic functionalization of alkylpyridines is an important pathway for pyridine derivatives synthesis. The reaction partners, however, were mostly limited to highly reactive polar electrophiles. Herein, we report a potassium amide‐catalyzed selective benzylic C−H bond addition of alkylpyridines to styrenes. Potassium bis(trimethylsilyl)amide (KHMDS), a readily available Brønsted base, showed excellent catalytic activity and chemoselectivity. A series of alkylpyridine derivatives, including benzylic quaternary carbon substituted pyridines, were obtained in good to high yield. Preliminary mechanistic studies revealed that the deprotonation equilibrium is probably responsible for the excellent selectivity. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of the unsymmetrically armed pincer PNNH (phosphine‐pyridyl‐pyrazole) ligand with FeCl2 yielded the five‐coordinate monomer [(PNNH)FeCl2], the NH proton of which captures THF through the formation of a hydrogen bond. Deprotonation of this NH functionality with Li[N(SiMe3)2] did not give the four‐coordinate [(PNN)FeCl], but instead retained LiCl to yield [(PNNLi)FeCl2], in which the lithium bridges between the pyrazolate β‐nitrogen and one of the chlorides on iron. One‐electron reduction of this compound under CO occurred with the loss of LiCl to form the square‐pyramidal monovalent iron in [(PNN)Fe(CO)2], which was characterized by IR, Mössbauer, and EPR spectroscopy, X‐ray diffraction, and DFT calculations. Cyclic voltammetry studies of [(PNN)Fe(CO)2] showed a reversible reduction wave and the reduction product was synthesized by using KC8. The product K[(PNN)Fe(CO)2] contains saturated, five‐coordinate Fe0; the (PNN)Fe subunit is anionic and the K+ cations cluster close to the pyrazolate side of the two CO ligands. Potassium electrophile complete its coordination sphere through interactions with the oxygen atom of a CO of a neighboring unit, thereby creating a polymeric chain. The reaction of [(PNN)Fe(CO)2] with HBpin (4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolane) resulted in the reduction of the metal center (by release of H2) and borylation of the pyrazole β‐nitrogen atom. This redox‐active addition of the H−B bond across the metal–ligand assembly is an unusual example of metal–ligand cooperativity and establishes a ligand that supports iron in three different oxidation states. [ABSTRACT FROM AUTHOR]

A simple method for the synthesis of highly functionalized 2‐amino‐6‐(methylthio)pyridine‐3,5‐dicarbonitriles is presented. In this method, pyridine derivatives are synthesized from the reaction of malononitrile, aromatic aldehydes, nitroketene dithioacetal in the presence of ethylene diamine. The notable features of this method are the simple Experimental procedure, short reaction time, and good yields. [ABSTRACT FROM AUTHOR]

5‐Methyl‐2,4‐dihydro‐3H‐pyrazol‐3‐one and/or 5‐methyl‐2‐phenyl‐2,4‐dihydro‐3H‐pyrazol‐3‐one was reacted with arylidenemalononitrile in the presence of sodium alkoxide to give 2‐amino‐6‐alkoxy‐4‐arylpyridine‐3,5‐dicarbonitrile 4a–e instead of the reported pyrazolo[3,4‐b]pyridine‐5‐carbonitriles. The same products 4a–e were prepared via reaction of arylidenemalononitrile with sodium alkoxide in an appropriative alcohol. However, the new synthetic route for preparation of their positional isomer 4‐amino‐6‐alkoxy‐2‐arylpyridine‐3,5‐dicarbonitrile 7a–j has been achieved via reaction of 2‐aminoprop‐1‐ene‐1,1,3‐tricarbonitrile with different aromatic aldehydes under the same conditions. [ABSTRACT FROM AUTHOR]

A Cu-catalyzed protocol for the synthesis of indolizine-containing diaryl- and triarylmethane derivatives through a 5- endo- dig cyclization of 2-(2-enynyl)pyridines, followed by a remote addition of nucleophiles, such as hydride and 2-naphthols, is described. [ABSTRACT FROM AUTHOR]

Bis adducts derived from a double Michael addition of rhodanine to an azo-ene system of two molecules of 1,2-diaza-1,3-dienes (DDs) have furnished the corresponding 2,3,5,6-tetrahydro-1 H-pyrrolo[3,4- c]pyridine-1,3,6-triones by means of a CS2 extrusion/double cyclization sequence. The incorporation of two units (4 and 2 atoms) of DDs into the fused bicyclic heterocycles represents a new application of this versatile class of molecules in heterocyclic synthesis. [ABSTRACT FROM AUTHOR]

Four series of new push-push-pull chromophores based on two types of heterocyclic cores, namely imidazo- [5,1,2-cd]indolizines and naphtho[1',2':4,5]imidazo[1,2-a]pyridines, and two types of linear p spacers, namely diphenylacetylene and biphenyl, were prepared. The two isomeric heterocyclic compounds were prepared by palladium-catalyzed double C-H functionalization reactions. Further palladium-catalyzed C-C coupling reactions allow the construction of diphenylacetylene and biphenyl spacers on the chromophores. Different electron-donors including NMe2, NPh2, and OMe and CN acceptors were incorporated into the chromophores. The corresponding donor- and acceptor-free compounds were also prepared for comparative studies. In the case of chromophores with strong NMe2 or NPh2 donors, a strong intramolecular charge-transfer (ICT) process occurs leading to fluorescence emission quenching in polar solvents. The use of a slightly weaker OMe donor together with the naphtho[1',2':4,5]imidazo[ 1,2-a]pyridine core allows to obtain an intense blue fluorescence with high quantum yield of up to 0.825. DFT and TD-DFT calculations offer satisfactory explanations to the observed photophysical data. [ABSTRACT FROM AUTHOR]

Partitioning of neutron-poisoning lanthanides from minor actinides in used nuclear fuel using liquid-liquid separation techniques with moderately soft Lewis basic heterocyclic scaffolds is an area of intense research focus. Nitrogen heterocycles have demonstrated potential for the selective separation of Am3+ from Eu3+ in separations processes. Improved synthetic strategies are required to access more diversified complexant scaffolds for further study. The present work describes an efficient synthetic strategy for the preparation of functionalized [2,2′]-bipyridinyl scaffolds using Pd catalysis to prepare the requisite starting material and telescoped condensation to afford direct access to hemi-1,2,4-triazinyl-[2,2′]-bipyridines with aliphatic character and potentially greater solubility in less polar diluents. Synthetic method development, optimization, and substrate scope are reported herein. [ABSTRACT FROM AUTHOR]

An efficient and facile synthesis of cyanopyridines via a one-pot four-component reaction of aromatic aldehydes, acetophenones, malononitrile, or 2-aminoprop-1-ene-1,1,3-tricarbonitrile in presence of sodium alkoxide or ammonium acetate under both microwave and thermal reaction conditions was introduced. [ABSTRACT FROM AUTHOR]

Self-assembly of 1:1:2 MII(BF4)2 (M=Zn or Fe), pyrazine-2,5-dicarbaldehyde ( 1) and 2-(2-aminoethyl)pyridine gave trimetallic triangle architectures rather than the anticipated tetrametallic [2×2] squares. Options for the nontrivial synthesis of 1 are considered, and synthetic details provided for both preferred routes. Rare cyclohelicate triangle architectures are observed for the pair of structurally characterized yellow-brown [Zn3 L3](BF4)6 and dark green [Fe3 L3](BF4)6 complexes of the neutral bis-terdentate Schiff base L. In order to form these pyrazine-edged triangles, the octahedral metal ions-with all 6 N-donors provided by the terdentate binding pockets of two L-are located 0.4-0.5 Å out of the plane of the bridging pyrazines, towards the center of the triangle. Density functional theory calculations confirm that simple particle counting entropic arguments, which predict triangles over squares, are correct here, with the triangles shown to be energetically favored over the corresponding squares. However, importantly, DFT analysis of these and related triangle versus square systems also show that vibrational contributions to entropy dominate and may significantly influence the preferred architecture, such that simple particle counting cannot in general be reliably employed to predict the observed architecture. [ABSTRACT FROM AUTHOR]

A new series of octahedral rhodium(III) complexes 1- 8 of the type [(L n)2Rh(dppz)]Cl ( n = 1-6) and [(L n)2Rh(dppz)](PF6) { n = 1, 7, 8; L = 2-phenylpyridine, with different modifications, as the C,N-chelating ligand; and dppz = dipyrido[3,2-a:2′,3′- c]phenazine} have been synthesized and fully characterized. The photophysical properties of the complexes have been investigated. The single-crystal X-ray diffraction structures of five complexes - [(L1)2Rh(dppz)](PF6), [(L2)2Rh(dppz)]Cl, [(L3)2Rh(dppz)](PF6), [(L4)2Rh(dppz)](PF6), and [(L8)2Rh(dppz)](PF6) - have confirmed the anticipated structure and have revealed the effect of substitution on the structure of the complex, which has been reasonably explained through experimental electrochemical characterization. The interaction of complexes 1- 8 with calf thymus DNA (CT DNA) has been verified by the fluorescent detection of ethidium bromide (EB) displacement studies. The result clearly suggests that the DNA-binding abilities of these Rh complexes are not only influenced by the DNA-intercalator dppz, but are also highly influenced by the electronic and steric properties of the C,N-chelating ligands. [ABSTRACT FROM AUTHOR]

New diquat derivatives based on [1,2,3]triazolo[1,5- a]pyridine and [1,2,3]triazolo[1,5- a]quinoline have been synthesized in excellent yields. To evaluate the effect of the alkyl bridge length, ethane and propane dibromo alkane substrates were used for their synthesis. Theoretical calculations predicted a very small energetic barrier between the two possible enantiomers P ( Ra) and M ( Sa), which makes them very difficult to resolve. Thermal denaturation studies, UV/Visible spectroscopy, and fluorescence titrations with ct-DNA evidenced the intercalation of the quinoline derivatives in DNA. [ABSTRACT FROM AUTHOR]

A simple and convenient procedure for the preparation of some unknown 2,3-disubstituted 5-iodo-1 H-pyrrolo[2,3- b]pyridines from readily available starting materials by Fischer indole cyclization in polyphosphoric acid is described. The present methodology provides an alternative synthetic approach to the synthesis of 5-iodo-7-azaindole scaffold. All synthesized compounds were characterized by IR, MS, 1H and 13C NMR, and elemental analysis. [ABSTRACT FROM AUTHOR]

A synthesis of bis(dihydropyridine-3,5-dicarbonitrile) by a three-component reaction of one equivalent of bis-cyanoacetamides with two equivalents of both arylaldehydes and malononitrile in ethanol-containing piperidine is reported. Bis-cyanopyridones could also be obtained by the condensation of bis-cyanoacetamides with substituted arylidenemalononitriles in the presence of piperidine, chitosan, or montmorillonite as basic catalysts. The cytotoxicity of the synthesized products against the heterogeneous human epithelial colorectal adenocarcinoma cell line (Caco-2) was assessed by WST-1 assay with concentration dependent cellular growth inhibitory effect especially for compounds 5l, 5h, and 5d. The dose response curves indicate that IC50 were 87 ± 3.11 μg/mL, 104 ± 4.78 μg/mL, and 108 ± 5.12 μg/mL, respectively. [ABSTRACT FROM AUTHOR]

A series of some substituted diethyl 4-(2-chloroquinolin-3-yl)-2,6-dimethylpyridine-3,5-dicarboxylates has been synthesized from substituted diethyl4-(2-chloroquinolin-3-yl)-1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylates (1,4-DHPs) by treating the latter with SiO2-HNO3 which proved to be a better oxidant in terms of product yield, reaction time, and cost. Further, these compounds were screened for their antimicrobial activity. All the diethyl 4-(2-chloroquinolin-3-yl)-2,6-dimethylpyridine-3,5-dicarboxylates exhibited more potent activities than the corresponding 1,4-DHPs. Further, docking simulation of the most active and least active compounds 3e and 2e into Escherichia coli topoisomerase II DNA Gyrase B was also performed. [ABSTRACT FROM AUTHOR]

Salts of anionic silver(I) clusters with the carba- closo-dodecaboranylethynyl ligand were obtained from {Ag2(12-C≡C- closo-1-CB11H11)} n, selected pyridines, and [Et4N]Cl or [Ph4P]Br. Salts of octahedral silver(I) clusters [Et4N]2[Ag6(12-C≡C- closo-1-CB11H11)4(4-X-C5H5N) x] were formed with pyridine (X=H, x=8), 4-methylpyridine (X=Me, x=8), and 4-cyanopyridine (X=CN, x=10). In contrast, 3,5-lutidine (3,5-Me2Py) did not result in salts of dianionic clusters, even in the presence of excess of [Et4N]Cl or [Ph4P]Br; instead salts of monoanionic AgI7 clusters, [Et4N][Ag7(12-C≡C- closo-1-CB11H11)4(3,5-Me2Py)9] and [Ph4P][Ag7(12-C≡C- closo-1-CB11H11)4(3,5-Me2Py)13] were obtained. The AgI7 cluster is pentagonal bipyramidal in the former, but is an edge-capped octahedron in the latter. The 4-methylpyridine and 3,5-lutidine complexes show green phosphorescence at room temperature. Although argentophilic interactions give rise to sufficient spin-orbit coupling for intersystem crossing S1→T n and moderate-to-high radiative rate constants, time-resolved measurements indicate that the quantum yields are greatly influenced by the pyridine ligands, which mainly determine the non-radiative rate constants. In addition, the crystal structures of [Ag16(12-C≡C- closo-1-CB11H11)8(Py)9.25(CH3CN)2(CH2Cl2)0.75] ⋅CH2Cl2, [Ag8(12-C≡C- closo-1-CB11H11)4(Py)12], [Ag10(12-C≡C- closo-1-CB11H11)4(4-MePy)10Br2], [Ag7(12-C≡C- closo-1-CB11H11)3(4- tBuPy)11Cl] ⋅(4- tBuPy), and [Ag9(12-C≡C- closo-1-CB11H11)4(3,5-Me2Py)11Cl] were elucidated. [ABSTRACT FROM AUTHOR]

A highly efficient one-pot synthesis of polysubstituted pyridine has been achieved through copper-catalyzed oxidative sp3 C−H coupling of acetophenones with toluene derivatives. Besides, the polysubstituted benzene was obtained through copper-catalyzed coupling of acetophenones. Both of the reactions exhibited a good functional group tolerance to produce a 2,4,6-triphenylpyridine or 1,3,5-triarylbenzene in high yields. Compared with previous methods, these transformations allow a highly flexible and efficient preparation of substituted pyridines and benzenes. [ABSTRACT FROM AUTHOR]

In order to study the influence of heterocyclic nuclei on the photochemical behavior of conjugated butadiene systems, novel butadiene derivatives E, Z- and E, E-2/3-[4-(2-vinylphenyl)buta-1,3-dienyl]thiophene as well as E, Z- and E, E-3/4-[4-(2-vinylphenyl)buta-1,3-dienyl]pyridine have been synthesized. The Wittig reaction was utilized in a two-step reaction course. During the first Wittig reaction, the corresponding aldehydes, namely 2/3-thiophenecarboxaldehyde and 3/4-pyridinecarboxaldehyde, reacted with formylmethylenetriphenylphosphorane to give the corresponding acrylaldehydes, which reacted with the diphosphonium salt of α,α′- o-xylenedibromide in the second Wittig reaction to give new butadiene derivatives. These butadiene derivatives afforded, by photochemical intramolecular cycloaddition, new fused tricyclic as well as tetracyclic derivatives. For the first time, a study of efficiency was conducted where the efficiency of intramolecular cycloaddition of these heterocyclic butadiene derivatives was investigated by simultaneous use of ferrioxalate and valerophenone actinometers. [ABSTRACT FROM AUTHOR]

Treatment of 2-cyano- N′-(1-(pyridin-2-yl)ethylidene)acetohydrazide 1 with aromatic/heterocyclic aldehydes 2a-f gave arylidene derivatives 3a-f. Polysubstituted pyridine derivatives 4a,b were prepared either from reaction of arylidene 3a,b with malononitrile or from reaction of acetohydrazide 1 with arylidenemalononitrile 5a,b. Cyclocondensation of acetohydrazide 1 with salicylaldehyde derivatives and acetylacetone furnished pyrido-coumarins 6,7 and 2-pyridone-3-carbonitrile 8, respectively. In addition, pyrido-thiazoles 13 and 15 were obtained through reaction of 2-(1-(pyridin-2-yl)ethylidene)hydrazinecarbothioamide 11 with hydrazonyl chlorides and α-haloketones, respectively. The structures of synthesized compounds were elucidated with spectral and elemental data. The antimicrobial activity of the synthesized compounds was studied. [ABSTRACT FROM AUTHOR]

10,15,20-Tris(pentafluorophenyl)-substituted NiII-porphyrin meso-oxy radical bearing two coordinating pyridines was synthesized as a stable radical with a quartet ground state ( S=3/2). X-ray structural analysis revealed that the NiII porphyrin moiety is fairly planar and the Ni−N bond lengths are considerably longer, indicating the high-spin state of the NiII center. The radical exhibited a quartet ground state, indicating the ferromagnetic interaction between the high-spin NiII center ( S=1) and the porphyrin meso-oxy radical ( S=1/2). [ABSTRACT FROM AUTHOR]

The photocatalyzed addition of several hydrogen donors (ethers, aldehydes, alkanes, amides) onto vinylpyridines was achieved. This approach provided access to alkylpyridines, which are important building blocks for the preparation of compounds with biological activity. The strategy was very simple and straightforward because it required only a small amount of a cheap decatungstate salt as photocatalyst. As an added advantage, the reaction could be performed under sunlight irradiation as well as under flow conditions. [ABSTRACT FROM AUTHOR]

4-Oxo-1-phenyl-4,7-dihydropyrazolo[3,4- b]pyridine-5-carbonitrile compound ( 4) was prepared by the reaction of 5-amino-3-methyl-1-phenyl pyrazole ( 1) with ethyl 2-cyano-3-ethoxyacrylate followed by cyclization using diphenyl ether. The pyrazolopyridinone compound 4 was converted to the chloropyrazolopyridine 5 by the reaction with phosphorus oxychloride. Compound 5 was used as a starting material to synthesize 3-amino-4-substituted pyrazolothienopyridine derivatives 10a-f and ethyl-3-aminopyrazolopyrrolopyridine-2-carboxylate 21, which were used as a versatile precursors for synthesis of poly-fused heterocyclic compounds. [ABSTRACT FROM AUTHOR]