Among the organic molecules, the so called push-pull or dipolar molecules (D-π-A) offer versatility of synthesis and ability to modulate their photophysical and photochemical properties.

The cyanoacetic acid moiety has been used extensively as the acceptor group in D-π-A molecules motivated by its easy/inexpensive synthesis and ability to simultaneously act as a strong electron withdrawing moiety, as well as a stable anchoring group in dye-sensitized solar cells (DSSCs).^[1]

Our previous work on the synthesis and characterization of D-π-A chromophores in which the donor part (D) is represented by a p-excessive five-membered heteroaromatic system (pyrrole or thiophene) functionalized by electron donor groups and the acceptor part (A) is a strong electron acceptor group (“classical” or an electron-deficient heterocycle) has shown that they exhibit excellent solvatochromic, photochromic, emissive properties, good photovoltaic efficiencies, exceptional thermal stabilities and good to excellent NLO responses.^[2]

In this work, we report the synthesis of new D-π-A chromophores functionalized with cyanoacetic acid as acceptor group, linked to the thienylpyrrole heterocyclic system, which plays the dual role of π-bridge and auxiliary donor group. Thienylpyrrolyl-cyanoacetic acid derivatives were obtained in excellent yields through a simple Knoevenagel condensation of the corresponding precursor aldehydes with cyanoacetic acid in acetonitrile at reflux, using piperidine as catalyst, and the optical and solvatochromic properties of the novel push-pull systems were evaluated.

References:

1. (a) Park, K.-W.; Serrano, L. A.; Ahn, S.; Baek, M. H.; Wiles, A. A.; Cooke, G.; Hong, J. Tetrahedron 2017, 73 (8), 1098-1104; (b) Ortega, E.; Montecinos, R.; Cattin, L.; Díaz, F. R.; del Valle, M. A.; Bernède, J. C. J. Mol. Struct. 2017, 1141, 615-623; (c) Zhang, L.; Cole, J. M. ACS Appl. Mater. Interfaces 2015, 7 (6), 3427-3455.
2. (a) Fernandes, S. S. M.; Castro, M. C. R.; Mesquita, I.; Andrade, L.; Mendes, A.; Raposo, M. M. M. Dyes Pigments 2017, 136, 46-53; (b) Fernandes, S. S. M.; Mesquita, I.; Andrade, L.; Mendes, A.; Justino, L. L. G.; Burrows, H. D.; Raposo, M. M. M. Org. Electron. 2017, 49, 194-205; (c) Garcia-Amorós, J.; Castro, M. C. R.; Coelho, P.; Raposo, M. M. M.; Velasco, D. Chem. Comm. 2016, 52 (29), 5132-5135; (d) Castro, M. C. R.; Belsley, M.; Raposo, M. M. M. Dyes Pigments 2016, 131, 333-339; (e) Pina, J.; Seixas de Melo, J. S.; Batista, R. M. F.; Costa, S. P. G.; Raposo, M. M. M. J. Org. Chem. 2013, 78 (22), 11389-11395; (f) Coelho, P. J.; Castro, M. C. R.; Fernandes, S. S. M.; Fonseca, A. M. C.; Raposo, M. M. M. Tetrahedron Lett. 2012, 53 (34), 4502-4506; (g) Pina, J.; de Melo, J. S. S.; Batista, R. M. F.; Costa, S. P. G.; Raposo, M. M. M. Phys. Chem. Chem. Phys. 2010, 12 (33), 9719-9725; (h) Batista, R. M. F.; Costa, S. P. G.; Malheiro, E. L.; Belsley, M.; Raposo, M. M. M. Tetrahedron 2007, 63 (20), 4258-4265.

Acknowledgements

Thanks are due to Fundação para a Ciência e Tecnologia (Portugal) for financial support through project PEst-C/QUI/UI0686/2011 (F-COMP-01-0124-FEDER-022716), FEDER-COMPETE and a post-doctoral grant to R.M.F. Batista (SFRH/BPD/79333/2011). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network, and was purchased with funds from POCI2010 (FEDER) and FCT.

The Suzuki-Miyaura cross coupling reaction is a very powerful tool for making of C–C bonds from organic halides and organoboron compounds [1]. This reaction, for which palladacycles have shown great catalytic activity [2] is widely employed in academic laboratories as well as in pharmaceutical industries to synthesize organic compounds or drugs such as Losartan [3], an antihypertensive medicine.

Iminophosphoranes are organic compounds of general composition R₃P=NR and can be used as in coordination and in organometallic chemistry [4]. The aim of this work is to study the catalytic activity of new palladium organometallic compounds derived from iminophosphorane ligands.

References

[1] N. Miyaura, K. Yamada, A. Suzuki; Tetrahedron Letters, 1979, 20, 3437 

[2] W.A. Herrmann, C. Brobmer, K. Öfele, C.-P. Reisinger, T. Priermeier, M. Beller, H. Fischer; Angew. Chem., 1995, 107, 1989

[3] Smith, G. B.; Dezeny, G. C.; Hughes, D. L.; King, A. O.; Verhoeven, T. R. J. Org. Chem. 1994, 59, 8151.

[4] Pingrong Wei, Katie T. K. Chan and Douglas W. Stephan; Dalton Trans., 2003, 3804

Acknowledgments

We wish to thank the financial support received from the Xunta de Galicia (Galicia, Spain) under the Grupos de Referencia Competitiva Programme Projects GRC2015/009.

The substituted amine-bis(phenol) compound N,N-bis-(4,5-dimethyl-2-hydroxybenzyl)-N(2-pyridylethyl)amine (H₂L) was prepared through a Mannich reaction utilizing two equivalents of a substituted phenol, two equivalents of formaldehyde and a single equivalent of a secondary amine. The organic compound, which may act as a tripodal ligand in coordination complexes, has been characterized by elemental analysis, IR, and ¹H and ¹³C NMR spectroscopies, mass spectrometry (ES) and X ray diffraction spectroscopy.

Thiosemicarbazone ligands are usually [N,S] donors rendering diverse coordination compounds and as [C,N,S] donors they give organometallic complexes. In this work, an unexpected isomerization of a C=N bond in a thiosemicarbazone is described.

The ligands used in this work have been synthesized by condensation reactions and the final product shows an E configured double bond as expected. However, after reaction with palladium salts, the structure of these ligands changes, to give complexes with a C=N Z configuration. This observation has been confirmed by X−ray diffraction studies.

It is not easy to change a double bond from E configuration to Z, therefore this achievement could open a door to investigate new synthetic pathways for isomerizing the C=N double bond in thiosemicarbazones and in related ligands.

1,5-Disustituted tetrazoles (1,5-DS-T) are useful heterocyclic moieties present in many bioactive compounds and drugs. Moreover, they are used as bidentate ligands in coordination chemistry, metal-organic framework science, bioimaging, photo-imaging, explosives, propellants, and high energy materials. In this work we report a series of ten new bis-heterocycles type spacer containing 1,5-disubstituted-1H-tetrazoles and furan, synthesized via Ugi-azide (UA) MCR in good to excellent yields (79-99%), using furfuryl amine as constant component and varying the aldehyde and isocyanide components in mild conditions. Additionally, the furan ring present in this bis-heterocycle has great importance in Diels-Alder cycloaddition reaction. As per our knowledge, there are no any previous reported methods available toward bis-heterocycles type spacer via UA.

The purpose of this paper was to study the curing kinetics of an epoxy system composed of  Diglicidil Ether of Bisphenol A (BADGE n = 0) epoxy resin and the meta-xylylenediamine (m-XDA) hardener with  nanoparticles of gold and nanoclay type montmorillonite. It is intended to be able to arrive at a kinetic equation that could describe reaction rateas a function of curing degree for all the conversion range, using the model proposed by Kamal et al.

The mononuclear complex [Dy(H₃L)(H₂O)(NO₃)](NO₃)₂ (Dy) and the heterotrinuclear compound [Zn₂Dy(L)(NO₃)₃(OH)]·3H₂O (Zn₂Dy·3H₂O) can be obtained with the same H₃L compartmental ligand. The single X-ray crystal structure of the both complexes shows a DyO₉ core but with different geometries: a muffin-like disposition in Dy and a spherical capped square antiprism in Zn₂Dy. The luminiscent characterisation of the metal compounds in methanol solution at 298 K shows a notable increase in the fluorescent emission of the heterotrinuclear complex respect to the mononuclear one, indicating that the presence of zinc improves significantly the fluorescent character of Zn₂Dy·3H₂O respect to Dy. Accordingly, Zn₂Dy·3H₂O could be a potential fluorescent probe for imaging applications.

The spiro-regioisomers 1a and 1b were synthesized from the xanthate-type precursor 2 via a free-radical mediated spirocyclization in different proportions depending on the reaction temperature, from 40:1 at -45 °C to 5:1 at 150 °C. The maximum proportion relationship value was 2:1 at 110-125 °C. We hypothesize that those proportion values are due to inherent stability of the involved free radicals. In the case of the product 1a, the intermediate is a very thermodynamically stable double allyl radical. In the case of the product 1b, the intermediate is an a,b,g,d-unsaturated carbonyl radical. The products 1a-b were fully characterized by ¹H and ¹³C NMR, FT-IR, HRMS, and even by X-ray analysis because adequate crystals were obtained for both products, (1a, CCDC: 1050852) and (1b, CCDC: 1050853) respectively.

Imidazole and its derivatives form an important class of heterocycles because of their abundance in naturally occurring molecules and broad medicinal applications. They possess activities such as antibacterial, antiinflammatory, antiallergic, analgesic, antifungal, kinase inhibition, antagonists, antitumor, and fungicidal actions. ¹­­­­

In the last decade, several methods have been reported for synthesis of highly substituted imidazole derivatives.² However, many of the reported synthetic protocols for the synthesis of imidazoles have limitations in terms of the use of excess amounts of toxic catalysts, formation of byproducts and unsatisfactory yields, lengthy reaction times, difficult work-up and significant amounts of waste materials. Therefore, development of new methodologies and introducing recoverable catalysts to overcome aforementioned disadvantages is still desirable and is in demand.

In continuation of our ongoing efforts^3-5 to develop efficient catalysts for different MCRs, we report herein the catalytic application of a 1,3,5-Tris (2-hydroxyethyl) isocyanurate-Cu(II) functionalized magnetic graphene (MGO-THEIC-CuII), as a new, highly efficient and recoverable catalyst, for the synthesis of 2,4,5-trisubstituted imidazoles derivatives under microwave irradiation.

Refrences:

 (1)Shirole, G. D.; Kadnor, V. A.; Tambe, A. S.; Shelke, S. N. Research on Chemical Intermediates 2017, 43, 1089.

 (2)Maleki, A.; Alrezvani, Z.; Maleki, S. Catalysis Communications 2015, 69, 29.

 (3)Dekamin, M. G.; Arefi, E.; Yaghoubi, A. RSC Advances 2016, 6, 86982.

 (4)Dekamin, M. G.; Eslami, M. Green Chemistry 2014, 16, 4914.

 (5)Dekamin, M. G.; Peyman, S. Z. Monatshefte für Chemie-Chemical Monthly 2016, 147, 445.

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The decomposition pathways of the anionic parts of the 5,5'-bitetrazole-related energetic salts are studied theoretically using highly-symmetric 5,5'-bitetrazole-1,1'-diide (point group D_2d) as a model compound. The relaxed scans for all the four symmetry unique bonds elongation have been performed at the wB97XD/6-311+G(d,p) level of theory. The results have revealed that the most preferable decomposition route is the C5—N1 bond elongation. Breaking of the bonds has been tracked using the QTAIM analysis at each point along the reaction coordinate. Another decomposition mechanism of 5,5'-bitetrazole-1,1'-diide can be triggered by its oxidation, which results in breaking of the N2—N3 bond.