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Decomposition of the polycation Al 13 O 4 (OH) 24 (H 2 O) 12 7+ (Al 13) promoted by ligand is a vital subject to advance our understanding of natural and artificial occurrence and evolution of aluminum ions, especially in the case of acidic condition that dissolved Al3+ species can be released from the Al-bearing substances. However, the microscopic pathway of synchronous proton-promoted and ligand-promoted decomposition process for Al 13 is still in the status of ambiguity. Herein, we applied differential mass spectrometry method and DFT calculation to study the initial detailed process of Al 13 decomposition under the presence of proton and salicylic acid (H 2 Sal). Mass results showed that the mononuclear Al3+-H 2 Sal complexes dominated the resulting Al species, whereas the monodentate complex Al 13 HSal6+ was not observed in the spectra. The difference of decomposition levels between the ligand/Al ratio 0.2 and 0.5 cases revealed that proton and ligand performed synergistic effect in initial Al 13 decomposition process, and the proton transfer determined the ring closure efficiency. The ring closure reaction is the prerequisite for the collapse of Al 13 structure and detachment of the mononuclear complex. DFT calculations reveal that hydrogen bond plays an important role in inducing the formation of chelated complex accompanying proton transfer. Attachment of protons at the bridging OH− can elongate and weaken the critical bond between targeted Al3+ and µ 4 -O2- resulting from delocalization of electron pairs in the oxygen atom. These results demonstrate the detailed mechanism of Al 13 composition promoted by ligand and proton, and provide significant understanding for further application and control of Al 13. [Display omitted] [ABSTRACT FROM AUTHOR]

• T3P® was used in a Robinson – Gabriel synthesis. • Efficient synthesis of bacterial and unnatural 5-(3-indolyl)oxazoles. • Avoid the use of toxic and hazardous water scavengers. In the present work, a propylphosphonic anhydride (T3P®) assisted Robinson–Gabriel cyclization of N -acyl-β-oxotryptamines for the synthesis of 2-substituted-5-(3-indolyl)oxazoles has been developed. The reactions proceeded smoothly in acetonitrile under microwave irradiation, and the product isolation required only an extraction and subsequent crystallization; no chromatography was necessary. The desired products were obtained in good to excellent yields. [ABSTRACT FROM AUTHOR]

[Display omitted] Cyclohex-2-enones have aroused great interest among chemists due to their wide natural occurrence and readily accessible functionalizations. Therefore, multiple synthetic methods have been developed for the construction of the cyclohex-2-enone ring. It has been found that some derivatives with a cyclohex-2-enone structure as the core nucleus exhibit a wide range of pharmacological activities, including anti-cancer, anti-bacterial, anti-inflammatory, anti-oxidative and anti-neuropathic properties. In this mini review, we summarize the synthetic methodology and exploration of biological activities of cyclohex-2-enone derivatives based on literatures especially reported in recent several years, which provides a reference for the comprehensive and systematic study of these compounds for medicinal purposes. [ABSTRACT FROM AUTHOR]

Abstract N -aminopyridyl ketone salts were reacted with formamide to yield heteroaromatic pyrido[2,1- f ][1,2,4]triazinium salts. Upon storage of these products in the presence of water, formation of covalent hydrates have been observed. Reaction of the same starting compound with urethane yielded 3-chloropyrido[2,1- f ][1,2,4]triazinium salt which readily reacted with secondary amines to afford 3-amino derivatives. An analogous ring closure reaction of 2-formylaminomethyl- and formaminobenzylpyridine allowed the synthesis of the partially reduced 3,4-dihydropyrido[2,1- f ][1,2,4]triazinium compounds. The cyclization procedure was also applied for the synthesis of the related pyrimido[2,1- f ][1,2,4]triazinium salt. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Heterocyclic nucleus plays a fundamental role in the medicinal chemistry and serves as a key template for the development of various therapeutic agents including broad spectrum antibacterial drugs. In an effort to develop new antibacterial agents, a bicyclic twelve-membered heterocyclic nucleus derived from coumarin was prepared by an uncomplicated method. The rate of ring closure for this nucleus, which was given the name coumacine, in addition to two of its derivatives was monitored spectroscopically and this rate followed zero order kinetics. The chemical structures of the synthesized products were established by detecting their physicochemical properties and analyzing their IR, 1H NMR and 13C NMR spectra. The in vitro antibacterial activity of coumacines was evaluated via agar dilution method against different standard aerobic and anaerobic bacterial strains using ciprofloxacin and metronidazole as positive controls, respectively; the results indicated that coumacine I has an excellent broad spectrum antibacterial activity against the tested bacterial strains with percentage of growth inhibition approximating to those of positive controls. [ABSTRACT FROM AUTHOR]

Established strategies for discovering selective kinase inhibitors are target-centric as they often target certain structural or reactive features in the target kinase. In the absence of such prominent features, there is a lack of general methods for discovering selective inhibitors. Here we describe a new strategy that exploits conformational flexibility of kinases for achieving selective kinase inhibition. Through ring closure, we designed and synthesized a panel of isoquinoline-containing compounds as rigidified analogs of an amidophenyl-containing parent compound. These analogs potently inhibit kinases including Abl and BRAF but have diminished inhibition against some other kinases compared to the parent compound. Sequence analysis reveals that many of the kinases that are potently inhibited by the isoquonoline-containing compounds contain a long insertion within their catalytic domains. A crystal structure of one rigid compound bound to BRAF confirmed its binding mode. Our findings highlight the potential of a novel strategy of rigidification for improving the selectivity of kinase inhibitors. [ABSTRACT FROM AUTHOR]

Conjugate addition reactions of 2,4-pentandione, dibenzoylmethane and ethylacetoacetate to enones have been investigated using Amberlyst-15 or Amberlyst-15-DMAP acetate system as catalysts. When 2,4-pentandione reactions were carried out in the presence of Amberlyst-15, conjugate addition and/or conjugate-addition initiated ring closure products were obtained depending on the reaction conditions. However, unlike 2,4-pentandione, dibenzoylmethane gave only conjugate addition products with Amberlyst-15. When Amberlyst-15-DMAP acetate system was used, always only conjugate addition products were obtained with β-dicarbonyl compounds independent of the reaction conditions. [ABSTRACT FROM AUTHOR]

Novel approach to CF 3 -/CHF 2 -oxazoles was developed. The key reaction was oxidation of fluoroalkyl enamides with PhI(RCO 2 ) 2 . [ABSTRACT FROM AUTHOR]

Representatives of a new compound family, 9-aryl-5 H -imidazo[2,1- d ][1,2,5]triazepin-6(7 H )-ones have been synthesized. As structural analogues of biologically active 1-aryl-2,3-benzodiazepine-4-ones, these compounds are potential drug candidates in the diseases of the central nervous system. An efficient five-step synthesis starting from imidazole is described here for the preparation of the target compounds. Shorter routes have also been studied, however, these attempts failed. [ABSTRACT FROM AUTHOR]

An unprecedented and convenient synthetic approach to 2,3-dihydro-1 H -isoindol-1-one (isoindolinone) derivatives has been developed. The key and final step of the method is the reaction of N -alkyl- N -( o -bromobenzyl)benzamides with butyllithium in THF at −78 °C. The corresponding 2-alkyl-3-aryl-2,3-dihydro-1 H -isoindol-1-ones were produced in moderate-to-fair yields, probably via oxidation of the initially formed corresponding 2 H -isoindole derivatives with air during workup. [ABSTRACT FROM AUTHOR]

A novel and efficient one-pot method has been developed for the synthesis of 1-substituted-3,4-dihydro-β-carbolines from tryptamine and a wide variety of carboxylic acids. The reaction was successfully applied to the synthesis of an important alkaloid harmalan as well as dihydro-eudistomin-U. This represents the first case in which 1-propanephosphonic acid cyclic anhydride (T3P®) has been used in the Bischler–Napieralski reaction. Unexpectedly it was observed that less than two equivalents of the T3P® reagent were sufficient for the two consecutive reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] Benzo[ b ]thieno[2,3- c ]quinolines were synthesized via Pd-catalyzed ring closure reaction of the α-aminophosphonates obtained by the Kabachnik–Fields condensation of benzo[ b ]thiophene-2-carboxaldehydes, 2-iodoanilines and diethyl phosphite or dibenzyl phosphite. The intramolecular cyclizations remained incomplete under the conditions applied. The products were isolated in 11–42% yields, and the unreacted starting materials were recovered from the reaction mixture. [ABSTRACT FROM AUTHOR]

Cyclic polymers present a topology that differ significantly from their linear counterparts due to their circular structure and therefore, the lack of chain ends. These simple characteristics are responsible for important unique properties (e.g. lower intrinsic and melt viscosity, lower hydrodynamic volumes, slower degradation profiles, increased blood circulation times and more selective bioaccumulation) thanks to which the cyclic polymers are today a vanguard in macromolecular chemistry. However, the preparation of cyclic polymers with high topological purity and in large quantities is challenging, therefore demanding the continuous development of synthetic methods. Advances in organic chemistry and the development of new catalytic systems has allowed the field of cyclic polymers to expand enormously in recent decades. In this review, ring closure and ring expansion polymerization strategies are described along the milestones that have characterized the evolution of cyclic (bio)polymer chemistry over the years. We also focus on very recent advances and state-of-the-art techniques for the synthesis and purification of cyclic polymers and provide an overview of properties and applications of cyclic polymers in different fields. [Display omitted] [ABSTRACT FROM AUTHOR]

The first generation of 2-bromo-3-lithioquinolines can be achieved and they are utilized for the preparation of 3-substituted 2-bromoquinolines. Thus, 2-(2,2-dibromoethenyl)phenyl isocyanides are treated with butyllithium in THF at −78 °C to generate these novel lithium compounds, which are allowed to react with various electrophiles to afford the corresponding desired products in one-pot. [ABSTRACT FROM AUTHOR]

Abstract: A wide range of dimethyl 2-(5-aryl-5-oxopentyl)malonates was electrooxidized in methanol, in the presence of catalytic amount of potassium iodide, to give the corresponding dimethyl 2-aroylcyclopentane-1,1-dicarboxylates in high yields. The reactions were carried out under extremely mild reaction conditions, in which the optimal amount of electrolytic current ranged from 2.24 to 2.35Fmol−1. The reaction presumably proceeded via a two-electron oxidation process, in which iodide ions played an important role as the electron carrier between the anode and the substrate. [Copyright &y& Elsevier]

Abstract: Representatives of a new family, 1-aryl-3H-pyrrolo[2,1-d][1,2,5]triazepin-4(5H)-ones have been synthesized at our laboratory as bioisosters of biologically active 1-aryl-2,3-benzodiazepine-4-ones. The efficient synthetic route described applies the synthesis of 2-(2-aroylpyrrol-1-yl)acyl hydrazides followed by ring closure under acidic conditions. The N(3)-unsubstituted title compounds thus obtained can optionally be N-alkylated rendering the preparation of variously substituted derivatives possible. Scope and limitations of the new protocol and some interesting side reactions are also discussed in detail. [Copyright &y& Elsevier]

Abstract: Variously substituted 2-phenyl-1,3-dioxolanes and 2-(2-bromophenyl)-1,3-dioxolanes, prepared from the corresponding benzaldehydes, were lithiated ortho to the acetal group. Reaction of the lithio derivatives with sulfur dioxide led to the lithium sulfinate salts, which gave, upon oxidative chlorination with sulfuryl chloride, the corresponding benzenesulfonyl chlorides. Then, depending on the aromatic substitution pattern of the molecule, several protocols were elaborated for the functional group transformations leading to the target compounds. Ring closure was performed with hydrazine hydrate or acetylhydrazine, in the latter case with one-pot removal of the acetyl group. The 4-unsubstituted 2H-1,2,3-benzothiadiazine 1,1-dioxides thus obtained are potential drug candidates based on their structural similarity to biologically active phthalazinones. [Copyright &y& Elsevier]

Abstract: Monoindolizinylquinoxalinepodands, easily available from indolizinylquinoxalines and various dihalides, undergo smooth oxidative dimerization in the presence of molecular iodine to afford corresponding macrocycles in good yields in a short reaction time. The use of inexpensive and readily available molecular iodine makes this method quite simple, more convenient, and practical. In solution the title macrocycles exist in an equilibrium of several conformations arising from restricted rotation around the Ind–Qx bonds (ca. C2 symmetrical and nonsymmetrical forms). The population of the forms and exchange rate between them depends strongly on the spacer type (length). [Copyright &y& Elsevier]

Abstract: Synthesis of O-perbenzoylated 3-(β-d-glucopyranosyl)-5-substituted-1,2,4-triazoles, precursors of potent inhibitors of glycogen phosphorylase, was studied by ring closures of N 1-acyl-carboxamidrazone type intermediates. Reactions of C-(β-d-glucopyranosyl)formimidate or C-(β-d-glucopyranosyl)formamidine with acid hydrazides as well as acylation of C-(β-d-glucopyranosyl)formamidrazone by acid chlorides unexpectedly gave the corresponding 1,3,4-oxadiazoles instead of 1,2,4-triazoles. The desired triazoles were obtained in reactions of C-(β-d-glucopyranosyl)formamidine or C-(β-d-glucopyranosyl)formyl chloride with arenecarboxamidrazones, and also in acylations of N 1-tosyl-C-(β-d-glucopyranosyl)formamidrazone with acid chlorides. Theoretical calculations (B3LYP and M06-2X DFT with the standard 6-31G(d,p) basis set) on simple model compounds with methyl and phenyl substituents to understand the bifurcation of the ring closure of N 1-acyl-carboxamidrazones indicated that in general the reaction led to 1,2,4-triazoles. However, the probability of the 1,3,4-oxadiazole forming pathway was shown to be significantly higher with N 1-benzoyl-acetamidrazones, which were closest analogues of the intermediates resulting in C-glucosyl-1,3,4-oxadiazoles. It was thereby demonstrated that the substitution pattern of the N 1-acyl-carboxamidrazones played a fundamental role in determining the direction of the ring closing reaction. [Copyright &y& Elsevier]

Abstract: A photo-activatable aziridinium precursor has been developed to investigate the possibility of a photo-initiated traditional nucleophilic reaction. The photolysis of a quaternary amine yields a tertiary amine and has allowed us to temporally control aziridinium formation and subsequent alkylation of a colorimetric nucleophilic reporter molecule. We have also used this photo-initiated reaction to alkylate a sulfhydryl group. This new photo-initiated alkylation strategy is water-soluble and expands the toolkit of photo-activated crosslinkers for protein labeling research. [Copyright &y& Elsevier]

Abstract: 2,2,5-Trisubstituted pyrrolidines of relevance to the core of kaitocephalin are readily available by an oxime ring closure using substrates derived from aspartic acid. [Copyright &y& Elsevier]

Abstract: A simple and efficient method for the synthesis of 2-(2-acylvinyl)-3-(5-alkyl-2-furyl)indoles by reductive recyclization of bis(5-alkyl-2-furyl)(2-nitroaryl)methanes is reported. This transformation was carried out by heating the substrates with SnCl2·2H2O in ethanol. The intermediate nitrosoarene moiety interacted with the furan ring via electrophilic nitrogen attack onto the C(2) position of the furan ring. It was shown that the related bis(5-alkyl-2-thienyl)(2-nitroaryl)methanes under the same reaction conditions failed to undergo the analogous recyclization and were transformed into bis(5-alkyl-2-thienyl)(2-aminoaryl)methanes. [Copyright &y& Elsevier]

Density functional theory (DFT) calculations of several 2-X-substituted phenyl cations (X = 2-CHO, 2-CH2OH, 2-CHS, 2-CHNH, 2-OCHNH, 2-SCHNH, 2-CHCH–CHCH2, 2-CHCH2 and 2-NO2) have been carried out in the gas phase and in acetonitrile (MeCN) at the B3LYP/6-31G(d,p) level of theory. The stationary point geometry of these aryl cations have been found to be in strong dependency of the medium. In the gas phase, unexpected behavior of considered aryl cations takes place resulting in the rearrangement or ring closure reaction. Such the cyclization reaction is proceeding via the nearby atom of the substituent which appears in relative vicinity (up to ∼3 Å) to the cationic center. Only in the case of 2-NO2 derivative, the geometry optimization has lead to rearranged quazi-quinoid structure of the cation that, obviously, takes place because of instability of the ring formed. Scan of the potential energy surface (PES) of 2-nitrophenyl cation has displayed no any reaction path leading toward the rearranged structure. Thus, the impossibility of existing of the singlet state of 2-nitrophenyl cation in the gas phase has been offered. The singlet–triplet transition of 2-nitrophenyl cation has been discussed in terms of the spin–orbit coupling (SOC) effects. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis of a series of benzo(iso)quinoline and phenanthroline derivatives has been achieved using an efficient one-pot procedure. It proceeds through a Suzuki–Miyaura cross-coupling followed by a Dieckmann–Thorpe ring closure under microwave irradiation and provides easy access to building blocks not readily available through other methods. [Copyright &y& Elsevier]

Abstract: A straightforward, two-step synthesis of fluoro substituted chromeno[2,3-c]pyrazol- and [1]benzothieno[2′,3′:5,6]pyrano[2,3-c]pyrazol-4(1H)-ones, respectively, is presented. Hence, treatment of 1-substituted or 1,3-disubstituted 2-pyrazolin-5-ones with fluoro substituted 2-fluorobenzoyl chlorides or 3-chloro-6-fluoro-1-benzothiophene-2-carbonyl chloride using calcium hydroxide in refluxing 1,4-dioxane gave the corresponding 4-aroylpyrazol-5-ols, which were cyclized into the fused ring systems. 5-Fluorochromeno[2,3-c]pyrazol-4(1H)-one was obtained upon treatment of the 1-(4-methoxybenzyl) protected congener with trifluoroacetic acid. Treatment of 5-fluorochromeno[2,3-c]pyrazol-4(1H)-ones with methylhydrazine afforded novel tetracyclic ring systems such as 2-methyl-7-phenyl-2,7-dihydropyrazolo[4′,3′:5,6]pyrano[4,3,2-cd]indazole. Detailed NMR spectroscopic investigations (1H, 13C, 15N, 19F) with the obtained compounds were undertaken. [ABSTRACT FROM AUTHOR]

Abstract: The regiochemistry of nucleophilic substitution of 4-phenylsulfonyl tetrafluoropyridine with unequal bidentate nucleophiles was investigated. The first nucleophilic substitution occurs at the 2-position of the pyridine ring by nitrogen nucleophile site (secondary or primary amine) followed by intermolecular ring closure at the geometrically accessible 3-position of the pyridine ring (by S, O and N nucleophiles). From this investigation, difluorinated tetrahydropyrido[3,4-b][1,4]oxazine, thiazine and pyrazine scaffolds were synthesized very readily by a one-pot annelation reaction of 4-phenylsulfonyl tetrafluoropyridine with appropriate unequal bidentate nucleophiles. [Copyright &y& Elsevier]

Abstract: A one-pot synthesis of novel poly-substituted phenanthrenes is described in this article through a Suzuki–Miyaura cross-coupling followed by a Dieckmann–Thorpe ring closure under microwave irradiation. The selection of the appropriate starting materials allowed us to introduce diversity on various positions of the phenanthrene ring system. [Copyright &y& Elsevier]

Abstract: A simple and convenient route is presented for the preparation of regio- and stereoisomers of novel azepane β-amino esters, starting from bicyclic β-lactam isomers. The synthetic procedure consists of dihydroxylation of the olefinic bond of the alicyclic amino esters, followed by NaIO4-mediated cleavage of the diol intermediate and reductive ring closure, which furnishes novel regioisomeric 5-aminoazepane-4-carboxylate and 3-aminoazepane-4-carboxylates. This method also allows the preparation of amino esters with an azepane skeleton in enantiomerically pure form. [Copyright &y& Elsevier]

Abstract: An efficient synthesis of 9,10-disubstituted phenanthrenes is described in this Letter. These novel useful building blocks were obtained in a one-pot reaction including Suzuki–Miyaura cross-coupling followed by a Dieckmann–Thorpe ring closure under microwave irradiation. The selection of the appropriate reagents and the optimal reaction conditions to isolate the intermediate biphenyl compound or the final substituted phenanthrenes in high yields will be discussed in this Letter. [Copyright &y& Elsevier]

Abstract: A convenient synthesis of 3-arylbenzo[b]thiophenes utilizing an interrupted Pummerer reaction of 2-(1-arylvinyl)phenyl ethyl sulfoxides is described. Thus, treatment of these sulfoxides, which were readily prepared from 2-sulfanylphenyl ketones or 2-fluoro-5-methoxybenzaldehyde, with acetic anhydride at 100°C afforded 3-arylbenzo[b]thiophenes in reasonable yields. [Copyright &y& Elsevier]

Abstract: Trials to prepare 2-azidothiazole in the lab led extensively to the isolation of thiazolo-tetrazole. In this paper an attempt has been made to investigate theoretically the factors which govern this ring closure isomerization on a quantitative basis. The structural parameters of 2-azidothiazole molecule which lead exclusively to the formation of the tetrazole have been investigated. The process of rotation of trans- to cis-2-azidothiazole and the process of ring closure of cis-2-azidothiazole to thiazolo-tetrazole have been investigated at a B3LYP/6-311G∗∗ level of the theory. The transition state in each process has been confirmed through vibrational analysis. The energy and the optimized geometry of the transition state have been determined. Results of computations in this work indicated clearly that the factors which lead to ring closure of azidothiazole to thiazolo-tetrazole start with the electronic structure of the thiazole ring where S-atom is bonded while it is in the ground state i.e., no hybridization. This behavior leads to a bond angle Ch name="sbnd" />C of ∼88° and a push-up of the azide group. The low rotational barrier of the azido group in the isomerization and the significant increase of the dipole moment of the tetrazole isomer are determining factors in ring closure tautomerization. The low values of the energies of the transition states favor cyclization. [Copyright &y& Elsevier]

Abstract: An efficient method to prepare 5, 9-cyclo-1, 11-oxido-pregn-16-ene-3, 20-dione in one pot was reported. Treatment of 9-bromide-11-hydroxypregna-1, 4, 16-trien-3, 20-dione with Raney Ni in absolute ethanol afforded 5, 9-cyclo-1, 11-oxido-pregn-16-ene-3, 20-dione by two annulation reactions in reasonable yield. The absolute configuration was also confirmed by X-ray crystal analysis. [Copyright &y& Elsevier]

Abstract: A short synthesis of alkyl 2-(bromomethyl)aziridine-2-carboxylates and alkyl 3-bromoazetidine-3-carboxylates was developed involving amination, bromination, and base-induced cyclization of alkyl 2-(bromomethyl)acrylates. These new small ring azaheterocyclic α- and β-amino acid derivatives are promising synthons as demonstrated by their transformation to 2-(aminomethyl)aziridine-2-carboxylates and 3-aminoazetidine-3-carboxylates. [Copyright &y& Elsevier]

Abstract: A straightforward synthesis of enantiopure (S)- and (R)-α-Tfm-pyroglutamic acid is reported. The strategy is based on the use of a chiral CF3-hydroxymorpholinone intermediate conveniently obtained from ethyl trifluoropyruvate-based chiral CF3-oxazolidines (Fox). The key step is an oxidative cyclization followed by a reductive cleavage of the (R)-phenylglycinol chiral auxiliary. [Copyright &y& Elsevier]

Abstract: One approach to designing RNA nanoscale structures is to use known RNA structural motifs such as junctions, kissing loops or bulges and to construct a molecular model by connecting these building blocks with helical struts. We previously developed an algorithm for detecting internal loops, junctions and kissing loops in RNA structures. Here we present algorithms for automating or assisting many of the steps that are involved in creating RNA structures from building blocks: (1) assembling building blocks into nanostructures using either a combinatorial search or constraint satisfaction; (2) optimizing RNA 3D ring structures to improve ring closure; (3) sequence optimisation; (4) creating a unique non-degenerate RNA topology descriptor. This effectively creates a computational pipeline for generating molecular models of RNA nanostructures and more specifically RNA ring structures with optimized sequences from RNA building blocks. We show several examples of how the algorithms can be utilized to generate RNA tecto-shapes. [Copyright &y& Elsevier]

Abstract: New examples of substituted thiazole derivatives carrying different heterocyclic ring systems at C-2 position were prepared via the reaction of several allenyl isothiocyanates with nucleophiles such as imidazoles, pyrazoles, benzimidazoles, indazole, 1,2,3-triazole, 1,2,4-triazole, and 1H-benzotriazole. Although these allenyl isothiocyanates are very reactive electrophiles and tend to polymerize, the yield of the thiazole products ranked between modest and very good. The regiochemistry of the reactions was proved by NMR and X-ray studies indicating that the attack of ambident nucleophiles proceeded very selectively. In some cases, however, the products were formed as mixtures of aromatic heterocycles and non-aromatic isomers. The latter could be rearranged to yield the uniform aromatic thiazoles. [Copyright &y& Elsevier]

Abstract: A new and convergent synthesis of the potent telomerase inhibitor RHPS4 is presented. The key step is the construction of the pentacyclic framework via an anionic ring closing cascade in which two new rings are formed. [Copyright &y& Elsevier]

Abstract: A simple strategy is presented for the introduction of a nitrogen atom into the carbocycle of an aminocyclopentenecarboxylic ester via dihydroxylation of the olefinic bond, followed by NaIO4-mediated cleavage of the diol intermediate and ring expansion, resulting in new regioisomeric 3-amino-4-piperidinecarboxylic acid derivatives. This method permits the preparation of amino esters with a piperidine skeleton in enantiomerically pure form. [Copyright &y& Elsevier]

Abstract: The effects of substituents on the rate of intramolecular cyclization of the 2,5-hexadienyl radicals have been investigated computationally with DFT theory, using the UB3LYP functional. Various substituents – CN, NO2, CH3, NH2, and t-butyl – at various positions – C1, C5 and C6 – were considered in the calculations. An electron-donating substituent on the C1 position raises the radical SOMO energies to increase the interaction with the alkene LUMO, whereas an electron-withdrawing counterpart lowers the SOMO and increases the interaction with the alkene HOMO. Both interactions decrease the activation energies, by 0.9–10.2kcal/mol, and increase the rate of reaction rate, from 3 to 2.7×107 times. Similar results were obtained for the substituents at the C6 position, and the activation energies for the intramolecular cyclization were decreased by 0.2–4.8kcal/mol and the reaction rate increased from 2 to 2.8×103 times. The substituent at the C5 position favors the formation of a 6-endo product because of a steric effect. The effects of disubstituents at both C1 and C6 positions were also investigated; the results showed that the electron-withdrawing groups decrease most effectively the activation energies. The so-called captodative effect was also investigated. [Copyright &y& Elsevier]

Abstract: Structurally related sets of triazino-quinoline, triazino-isoquinoline and pyrido-triazine derivatives were synthesised and their binding interactions with central (CBR)- and peripheral-type (PBR) benzodiazepine binding sites have been characterised. Of 33 compounds tested, a new compound, 2-(4-methylphenyl)-3H- [1,2,4] triazino [2, 3-a] quinolin-3-one (1 g) showed the lowest CBR binding inhibition constant (Ki =42±9 nM) and the highest CBR over PBR selectivity (>1300). All but the 4-methylphenyl (1 g) structural modifications decreased the affinity and selectivity of the parent compound, 2-phenyl-3H- [1,2,4]triazino[2,3-a]quinolin-3-one (1d) (Ki =69±9 nM, selectivity >890). Molecular interactions between selected ligands (standards and triazine derivatives) and α1γ2 subunit-interface residues in a GABAA receptor extracellular domain homology model have been calculated. Comparing data with calculations confirmed hydrogen bonding to γ2Thr142 and hydrophobic interaction with α1His101 as being essential for high-affinity CBR binding. [Copyright &y& Elsevier]

Abstract: New synthetic pathways have been elaborated to 1-methyl-1H-pyridazino[3,4-b]indoles starting from halopyridazin-3(2H)-ones. Suzuki cross-coupling reaction of chloro, iodo, dichloro, and dibromo substituted pyridazin-3(2H)-ones with 2-pivaloylaminophenylboronic acid followed by hydrolysis of the amide and subsequent ring closure via condensation gave fused indoles. Some of these compounds showed biological activity as antitrypanosomal agents. [Copyright &y& Elsevier]

Abstract: A number of methods by which various functional groups that are attached at the Cp-rings of Group 4 bent metallocenes can be intramolecularly coupled to yield ansa-metallocenes are presented and discussed. These methods include pathways of metallacyclopentane formation from Cp-alkenyl moieties, olefin metathesis reactions between α-olefins attached at the Cp-ligands, photochemically induced [2+2]cycloadditions of substituted vinyl groups and Lewis acid- or Brønsted acid-catalyzed Mannich-type condensation reactions between 1-aminoethenyl functional groups at the bent metallocene framework. The latter reaction type was also used for the formation of functionalized [3]ferrocenophane systems that provided a convenient entry to the synthesis of a variety of useful optically active [3]ferrocenophane-based chelate ligands for applications in asymmetric catalysis. [Copyright &y& Elsevier]

Abstract: The new ring-fused azepino[5,6-b]indole derivatives 3, 4 and 5 were prepared from diene precursors 8, 9, 13 and 15 in fair yields via a final ring-closing olefin metathesis. [Copyright &y& Elsevier]

Abstract: p-Toluenesulfonyl chloride (TsCl)/NaOH has been introduced as reagent combination for the synthesis of 2-amino-oxa- or 2-amino-thiazolidines from N-(2-hydroxyethyl)-thioureas, but its general application in heterocycle synthesis has not been investigated. In this paper the convenient and efficient synthesis of a variety of 2-amino-substituted 1-aza 3-(aza, oxo or thio) heterocycles of different substitution and ring sizes is described. The application of polymer-supported TsCl facilitates work-up and renders the reaction conditions very suitable for parallel or robot synthesis. [Copyright &y& Elsevier]

Reaction of C-2 substituted cyclohexenone with an enantiomerically pure α-bromopentenoate leads to enantiopure tricyclooctane, which can be transformed into a taxoid like compound having the typical bicyclo[5.3.1]undecane skeleton. [Copyright &y& Elsevier]

Suzuki coupling of 5-chloro-2-methyl-6-phenylpyridazin-3(2H)-one, 6-chloro-1,3-dimethyluracil and 2-chloropyrazine with protected aminoaryl boronic acids resulted in the corresponding pivaloylaminophenyl diazines which were transformed to diazino-fused indole and cinnoline derivatives. Suzuki coupling of 5-amino-6-chloro-1,3-dimethyluracil with 2-formylphenyl boronic acid afforded a novel pyrimidoisoquinoline ring system in a one-pot reaction. [Copyright &y& Elsevier]

Thermal properties of azidohetarenes without reactive ortho-substituents, obtained by DSC analysis, were compared with the DSC data of ortho-phenyl and ortho-acyl substituted azidohetarenes, which give ring closure reactions either to indoles or to five-membered heterocycles such as isoxazoles. The reaction temperatures and reaction enthalpies give both information to prepare the reaction conditions and important safety information and were, in addition, used to find out relations between the temperatures or enthalpies with the three different reaction mechanisms. [Copyright &y& Elsevier]

Suzuki cross-coupling reaction of 2-alkyl(methyl and benzyl)-5-chloro-4-methoxy- and 2-alkyl(methyl and benzyl)-4-chloro-5-methoxypyridazin-3(2H)-ones with 2-formylphenylboronic acid afforded the corresponding biaryl products which were cyclized with ammonia to yield hitherto undescribed pyridazino[4,5-c]isoquinolinones. Removal of the N-benzyl protective group in position 2 yielded the unsubstituted tricyclic pyridazinones. [Copyright &y& Elsevier]

[Display omitted] Complex assembly preferences and resultant spin state choice and Jahn-Teller distortion mode in twelve Mn(III) complexes of varying nuclearity with Schiff base chelate ligands of different sizes are compared. Mononuclear complexes Mn(5-F-Sal 2 323)]OTf (1), [Mn(5-F-Sal 2 323)]ClO 4 (2) and [Mn(5-F-Sal 2 323)]NO 3 , (3) with the 8-carbon R-Sal 2 323 chelate type show rare axial compression at room temperature and complexes (2) and (3) also show reversible thermal spin state switching from spin quintet to triplet states on cooling. The prevalence of atypical axial compression is further probed by single crystal diffraction studies on high spin mononuclear complexes (4)-(7) with the longer 9-carbon R-Sal 2 333 chelate series using [Mn(3-OEt-Sal 2 333)]BF 4 , (4) [Mn(3,5-diOMe-Sal 2 333)]BF 4 ·0.5PrOH, (5), [Mn(5-F-Sal 2 333)]BPh 4 , (6) and Mn(5-NO 2 -Sal 2 333)]BPh 4 , (7) as examples. Ring closure of both the 8-carbon R-Sal 2 323 and longer 9-carbon R-Sal 2 333 ligands was also observed yielding a ligand with a 6-membered ring in the mononuclear complex [Mn(3-OMe,5-NO 2 -Sal 2 3336R)]·0.07MeOH·0.93MeCN (8) in contrast to a protonated 5-membered ring in the dimeric complex [Mn 2 (5-Cl-Sal 2 323H5R) 2 ](ClO 4) 2 ·1.85EtOH·0.33MeCN, (9) with the R-Sal 2 323 chelate type. Finally comparison of the assembly modes of Mn(III) complexes of the 8-carbon R-Sal 2 323 and 9-carbon R-Sal 2 333 series with those of the shorter 7-carbon R-Sal 2 322 ligand series reveal that the mononuclear assembly mode is not favoured with the smaller chelate. Instead three dimeric or cluster complexes with rearranged ligands were recovered in low yield. The structures of these complexes [Mn 2 (5-NO 2 -Sal 2 3225R) 2 ]·2BuOH, (10), [Mn 2 (3,5-diBr-Sal 2 3225R)(3,5-diBr-Sal) 3 ]·0.7EtOH·2.61MeCN, (11) and [Mn 2 Na(3-NO 2 ,5-OMe-Sal 2 3225R)]ClO 4 ·0.5MeCN (12) are reported and compared with examples with the longer chain R-Sal 2 323 and R-Sal 2 333 chelate ligands. [ABSTRACT FROM AUTHOR]