New Azacycles by One-Pot Three-Component Hantzsch-Like Synthesis of Tetra(hexa)azacyclopenta[a]anthracenes, Tetraazaindeno[5,4-b]fluorenes, and Oxatetraazacyclopenta[m]tetraphenes.

New Azacycles by One-Pot Three-Component Hantzsch-Like Synthesis of Tetra(hexa)azacyclopenta[a]anthracenes, Tetraazaindeno[5,4-b]fluorenes, and Oxatetraazacyclopenta[m]tetraphenes (H. Butenschön, I. A. Abdelhamid et al.) #OpenAccess Multicomponent reactions (MCRs) are envisaged as an entry point for the synthesis of heterocyclic compounds with interesting biological activities. An efficient approach to annelated tetra(hexa)azacyclopenta[a]anthracenes, tetraazaindeno[5,4-b]fluorenes, and oxatetraazacyclopenta[m]tetraphene was accomplished using a three-component reaction involving 7-amino-2-methyl-3-phenylpyrazolo[1,5-a]pyrimidin-5-one with aromatic aldehydes and the corresponding active 1,3-dicarbonyl compounds (namely, dimedone, 1,3-dimethylbarbituric acid, 1,3-indanedione, and 4-hydroxycoumarine). The reactions were conducted in glacial acetic acid at reflux for 5 h to give the desired products in good yields (62-83 %). The chemical constitutions of all new products were confirmed spectroscopically.

Tetracyanobutadiene Bridged Push-Pull Chromophores: Development of New Generation Optoelectronic Materials.

This review describes the design strategies used for the synthesis of various tetracyanobutadiene bridged donor-acceptor molecular architectures by a click type [2+2] cycloaddition-retroelectrocyclization (CA-RE) reaction sequence. The photophysical and electrochemical properties of the tetracyanobutadiene bridged molecular architectures based on various moieties including diketopyrrolopyrrole, isoindigo, benzothiadiazole, pyrene, pyrazabole, truxene, boron dipyrromethene (BODIPY), phenothiazine, triphenylamine, thiazole and bisthiazole are summarized. Further, we discuss some important applications of the tetracyanobutadiene bridged derivatives in dye sensitized solar cells, bulk heterojunction solar cells and photothermal cancer therapy.

Synthetic Applications of Oxidative Aromatic Coupling-From Biphenols to Nanographenes.

Oxidative aromatic coupling occupies a fundamental place in the modern chemistry of aromatic compounds. It is a method of choice for the assembly of large and bewildering architectures. Considerable effort was also devoted to applications of the Scholl reaction for the synthesis of chiral biphenols and natural products. The ability to form biaryl linkages without any prefunctionalization provides an efficient pathway to many complex structures. Although the chemistry of this process is only now becoming fully understood, this reaction continues to both fascinate and challenge researchers. This is especially true for heterocoupling, that is, oxidative aromatic coupling with the chemoselective formation of a C-C bond between two different arenes. Analysis of the progress achieved in this field since 2013 reveals that many groups have contributed by pushing the boundary of structural possibilities, expanding into surface-assisted (cyclo)dehydrogenation, and developing new reagents.

Charge Transport through Ferrocene 1,1'-Diamine Single-Molecule Junctions.

The charge transport through ferrocene 1,1'-diamine (FDA) molecules between gold electrodes is investigated using the mechanically controllable break junction technique combined with a theoretical framework of density functional theory simulations to understand the physics of these molecular junctions. The characteristic conductances of the molecule are measured at low bias as well as current-voltage (IV) characteristics. By fitting the IV characteristics to the single-level model, the values for the position of the molecular level, mainly responsible for the transport, and its coupling to the leads, are obtained. The influence of the binding sites, molecular conformation, and electrode distance are systematically studied from a theoretical perspective. While a strong dependence of conductance on the adsorption geometry is found, the decrease of conductance as a function of electrode distance arises mainly from a decrease of coupling strength of the molecular electronic orbitals through a reduced overlap and, to a lesser extent, from a shift of their alignment with respect to the Fermi energy.

Comparison of oxidative aromatic coupling and the Scholl reaction.

Does the dehydrogenative coupling of aromatic compounds mediated by AlCl3 at high temperatures and also by FeCl3, MoCl5, PIFA, or K3[Fe(CN)6] at room temperature proceed by the same mechanism in all cases? With the growing importance of the synthesis of aromatic compounds by double C-H activation to give various biaryl structures, this question becomes pressing. Since some of these reactions proceed only in the presence of non-oxidizing Lewis acids and some only in the presence of certain oxidants, the authors venture the hypothesis that, depending on the electronic structure of the substrates and the nature of the "catalyst", two different mechanisms can operate. One involves the intermediacy of a radical cation and the other the formation of a sigma complex between the acid and the substrate. The goal of this Review is to encourage further mechanistic studies hopefully leading to an in-depth understanding of this phenomenon.

One electron oxidation of triferrocenylmethanol: synthesis, metal atom dynamics, electron delocalization, and the crystal structure of [Fc3COH](+) PF6⁻.

The title compound 2 was prepared and its crystal structure was determined at 100 K. The neat solid was examined by temperature dependent (57)Fe Mössbauer effect (ME) spectroscopy over the interval 92 < T < 318 K, and evidences two diamagnetic Fe(II) sites and one paramagnetic Fe(III) site. The latter shows spin-lattice relaxation, but there is no evidence of electron delocalization among the three iron sites in the above temperature interval. The mean-square-amplitude-of-vibration of the diamagnetic iron site has been determined from the recoil-free fraction ME resonance, and compared to the neutral Fc(3)COH homologue (1). The ME dynamical data are in good agreement with the U(i,j) value at 100 K extracted from the crystallographic results. The ME parameters at 5 K have also been determined with the sample compound embedded in a paraffin wax matrix as well as pelletized with BN.

Transannular addition of phenols to 1,1'-dialkynylferrocenes: unanticipated formation of phenoxy[4]ferrocenophanedienes.

The reaction of some 1,1'-dialkynylferrocenes with a variety of phenols in the presence as well as in the absence of [Mo(CO)(6)] yields good to high yields of phenoxy[4]ferrocenophanedienes. Similar reactivity was observed with a thiophenol and with acetic acid. Reaction under basic reaction conditions led to the formation of the [4]ferrocenophanone 17. The phenoxy[4]ferrocenophanedienes obtained show dynamic behavior as a result of a torsional twist of the carbon bridge as indicated by the (1)H and (13)C NMR spectra. The reaction mechanism is discussed in view of recent related results of Sato et al. as well as of Pudelski et al. A vinyl cation intermediate is postulated in this context, whose relative stability is evident from the mass spectra of the compounds prepared.

Metal atom dynamics in four triferrocenylmethane derivatives and the crystal structure of Fc3COH.

The metal atom dynamics of four triferrocenylmethane derivatives have been elucidated, using temperature-dependent 57Fe Mössbauer effect (ME) spectroscopy. The hyperfine parameters (IS and QS) at 90 K are compared to each other and those of related ferrocenoids. The metal atom vibrational amplitudes as a function of temperature have been extracted from the ME recoil-free fraction data, and are compared to the X-ray U(i,j) values for two of the compounds. The single crystal structural data for triferrocenylmethanol have been determined at 173 and 295 K. The vibrational anisotropy of the metal atom for all of the compounds is negligibly small over the accessible temperature range.

(S(P),S(P))-(-)-(E)-1,2-Bis(methyl-phenyl-phosphino-yl)ethene.

The title compound, C(16)H(18)O(2)P(2), possesses two stereogenic P atoms and shows a distorted s-cis conformation of each O=P-C=C moiety. This has been suggested on the basis of the stereochemical result of 1,3-dipolar cyclo-additions with nitro-nes and is now confirmed by the present crystal structure analysis. There are two crystallographically independent molecules in the asymmetric unit.

Asymmetric 1,3-dipolar cycloaddition with a P-stereogenic dipolarophile: an efficient approach to novel P-stereogenic 1,2-diphosphine systems.

The asymmetric 1,3-dipolar cycloaddition of the P-stereogenic dipolarophile (S(p),S(p))-6 to C,N-diphenylnitrone (7) led to previously unknown P-stereogenic isoxazolinyl diphosphine dioxides (R(p),S(p))-8 in enantio- and diastereomerically pure form; their stereospecific reduction with Ti(OiPr)(4)/PMHS proceeds in high yield with retention of configuration at the phosphorus atoms to give enantio- and diastereomerically pure diphosphines, which are conveniently purified via the corresponding diphosphine-diboranes.

Photooxygenation of 5-dialkylamino-4-pyrrolin-3-ones. Synthesis of highly functionalized ureas, 2-oxazolidinones, and 2-oxazolinones.

5-Dialkylamino-4-pyrrolin-3-ones, available from cyclocondensation of amidines with dimethyl acetylenedicarboxylate (DMAD), undergo rapid singlet oxygenation to give highly functionalized ureas by way of a 1,2-dioxetane cleavage of the initially formed [2 + 2] cycloadducts. These latter compounds undergo cyclization to 2-oxazolidinones in MeOH. Catalytic hydrogenation of the ureas in EtOAc gives 2-oxazolinones. The DBU-DMAD adduct undergoes photooxygenation by an entirely different pathway to give a large ring heterocycle.

The first cyclopentadienylalkylphosphane nickel chelates: synthesis, structures, and reactions.

The first cyclopentadienylalkylphosphane nickel chelate complexes are reported. The anionic ligand obtained by reaction of spiro[2.4]hepta-4,6-diene with lithium di-tert-butylphosphide was treated with NiCl2 to yield [eta(5):kappa(1)-(di-tert-butylphosphanylethyl)cyclopentadienyl]chloronickel(II). From this complex, some acetonitrile-stabilized cationic complexes were obtained by reaction with the respective silver salts in acetonitrile. Methyl- and alkynylnickel chelates were prepared by reaction of the chloronickel complex with methyllithium and by copper-mediated coupling with terminal alkynes, respectively. Some of the complexes prepared were investigated by X-ray crystallography or cyclic voltammetry. The alkynylnickel chelates undergo cycloaddition reactions with ethoxycarbonylisothiocyanate or tetracyanoethylene, and the cyclobutenes obtained undergo ring opening to the corresponding dienes. The study includes an NMR spectroscopic investigation of the two conformers of one of these dienes.

Unanticipated formation of ortho-sulfone substituted phenols by anionic thia-Fries rearrangement of (aryl triflate)tricarbonylchromium complexes.

Tricarbonylchromium complexes of aryl triflates undergo base-mediated anionic thia-Fries rearrangements to generate push-pull substituted [ortho-hydroxyaryl(trifluoromethylsulfonyl)phenol]tricarbonylchromium complexes under very mild reaction conditions.

Syntheses and structures of sterically congested linear and branched cobalta[n]triangulanes.

Treatment of {eta(5):eta(1)[2-(di-tert-butylphosphanyl-P)ethyl]cyclopentadienyl}cobalt(I) chloride (5) with methylenecyclopropane (3) or bicyclopropylidene (4), as well as with their spirocyclopropanated analogues methylenespiropentane (7), cyclopropylidenespiropentane (10), or 7,7'-bi(dispiro[2.0.2.1]heptylidene) (15) in the presence of sodium amalgam at -50 degrees C, furnished the stable cobalt complexes 6, 9, 8, 11, and 16, respectively, in 72, 83, 84, 86, and 54 % isolated yield, respectively. The complexes 14 and 16 were also obtained by ligand exchange of the ethene complex {eta(5):eta(1)[2-(di-tert-butylphosphanyl-P)ethyl]cyclopentadienyl}(eta(2)-ethene)cobalt(I) (12) with 13 and 15 in 79 and 52 % yield, respectively. The X-ray crystal-structure analyses of complexes 9, 14, and 16, as well as the NMR-spectroscopic data of all complexes, reveal that they can be regarded as linear and branched cobalta[n]triangulanes. The thermal stability of complexes 6, 8, and 9 up to 109, 145, and 160 degrees C was determined by differential thermal analysis-thermogravimetry (DTA-TG) analysis.

The synthesis and properties of bis-1,1'-(porphyrinyl)ferrocenes.

Ferrocene-bridged bisporphyrins have been synthesized by the condensation of corresponding dipyrromethane-derived diols with a bisdipyrromethane. Purification of the final compounds has been achieved without chromatography. The specific geometry of these bisporphyrins makes them valuable starting points for building complex molecular and supramolecular structures. In particular it provides a core to which multiple sites of attractive intermolecular interactions can be attached thereby creating compounds predisposed to form complex networks by association. We have studied the structure of bis-1,1'-(porphyrinyl)ferrocenes by 1H NMR, UV-Vis and electrochemistry. Results have shown that complex dynamic processes occur in these molecules (which may involve conformers, formation of H-aggregates and tautomers) and that they have non-typical electrochemical behaviour.

The first cobalt catalyzed [2 + 2 + 2] alkyne cyclotrimerization in aqueous medium at room temperature.

Chelate complex 1 (5 mol%) was found to catalyze the [2 + 2 + 2] cyclization of terminal alkynes in good yields in a 80/20 mixture of water and ethanol at room temperature without further activation.