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Facile synthesis of 4,5-dihydro-1,3,4-thiadiazoles by 1,3-dipolar cycloaddition of thioisomunchnones
No full textThe present paper summarizes a straightforward synthesis of 4,5-dihydro-1,3,4-thiadiazoles by the 1,3-dipolar cycloaddition of thioisomunchnones. These reactions have been carried out in dichloromethane and are essentially complete within 60 min at room temperature. Under such mild conditions the asymmetric version has been explored as well. Unequivocal structure elucidation has been accomplished by means of one- and two-dimensional NMR techniques as well as X-ray structure analysis
Synthesis and characterization of adducts of bis(O,O '-ditolyl/dibenzyl dithiophosphato)cobalt(II) with pyridine: Crystal structures of [Co{S2P(OC6H4Me-p)(2)}(2)(C5H5N)(2)] and [Co{S2P(OC6H4Me-p)(2)}(2)(NH3)]
No full textBis(O,O'-ditolyl/dibenzyl dithiophosphato)cobalt(II) complexes with pyridine ligands of the type [Co{S2P(OR)(2)}(2)(C5H5N)(2)] (R = o-, m-, p-C6H4Me, CH2Ph) have been synthesized by the reaction of CoCl2(C5H5N)(2) and the corresponding ammonium salt of O,O'-ditolyl/dibenzyl dithiophosphate in methanol. These newly synthesized adducts were characterized by elemental analysis, IR, UV-Vis spectroscopy, magnetic susceptibility measurements and single crystal X-ray diffraction. These structures confirm that in the pyridine complex the geometry around the cobalt metal centre is distorted octahedral, and in the amine complex it is distorted trigonal bipyramidal
Samarium diiodide-mediated intramolecular cyclodimerisation of bis-alpha,beta-unsaturated carbonyl compounds
No full textSamarium(II) diiodide-mediated intramolecular cycloclimerisation of simple bis-enones and -enoates in THF/MeOH has been investigated. Spirocyclic and elaborated polycyclic products, including stereodefined cis-bicyclo[3.3.0]octane and trans-bicyclo[4.3.0]nonanes, are obtained in synthetically useful yield
Synthesis of the non-adjacent bis-THF core of cis-sylvaticin using a double oxidative cyclisation
No full textA short synthesis of the non-adjacent bis-THF core of the Annonaceous acetogenin cis-sylvaticin (1) is described. C-2 Symmetrical (Z,E,E,Z)-and (E,E,E,E)-tetraenes 5 and 6 were synthesised in six and three steps respectively from (1E,5E,9E)-cyclododeca-1,5,9-triene. Subsequent permanganate promoted asymmetric bi-directional oxidative cyclisation of tetraene 5 was used to create the non-adjacent bis-THF core of 1, installing seven of the nine stereogenic centres present in the natural product in a single step. Desymmetrisation of the oxidative cyclisation product by mono-tosylation gave access to a C11-C32 fragment of cis-sylvaticin
Synthesis and spectroscopic characterization of tris(O,O '-ditolyl dithiophosphato) arsenic/antimony/bismuth(III) compounds: Crystal structures of [As{S<sub>2</sub>P(OC<sub>6</sub>H<sub>4</sub>Me-m)<sub>2</sub>}<sub>3</sub>]·0.5C<sub>6</sub>H<sub>14</sub>, [Sb{S<sub>2</sub>P(OC<sub>6</sub>H<sub>4</sub>Me-m)<sub>2</sub>}<sub>3</sub>] and [Bi{S<sub>2</sub>P(OC<sub>6</sub>H<sub>4</sub>Me-m)<sub>2</sub>}<sub>3</sub>]
No full textArsenic(III), antimony(III) and bismuth(III) compounds of the type, [M{S2P(OR)2}3] (where M = As, Sb and Bi; R = o-, m-, p-C6H4Me) were obtained by reactions of MCl3 with ammonium salts of the corresponding O,O'-ditolyl dithiophosphate on refluxing in benzene. These compounds were characterized by elemental analysis, IR, H-1 NMR and P-31 NMR spectroscopy. The single crystal X-ray structures of three representative compounds were determined. [As{S2P(OC6H4Me-m)2}3] · 0.5C6H14 crystallizes as triclinic in the space group P (1) over bar with a = 10.9396(1), b = 14.1891(2), c = 17.5359(2) angstrom, alpha = 70.731(1), beta = 84.734(1), gamma = 74.205(1)degrees, Z = 4,V = 2472.37(5) angstrom(3). [Sb{S2P(OC6H4Me-m)2}3] and [Bi{S2P(OC6H4Me-m)2}3] both crystallize as monoclinic in the space group P2(1) with a = 12.4520(3), b = 22.8760(5), c = 16.2165(4) angstrom, beta = 93.022(1)degrees, Z = 4, V = 4612.9(2) angstrom(3) and with a = 12.4903(2), b = 22.9554(4), c = 16.1032(3)angstrom, beta = 92.4300(10)degrees, Z = 4, V = 4612.96(14) angstrom(3), respectively. In all three molecules, the central metal atom is surrounded by all six sulfur atoms of the three chelating anisobidentate O,O'-ditolyl dithiophosphate groups in a pseudo trigonally distorted octahedron with a lone pair positioned on one of the triangular octahedral faces. The three metal sulfur bonds adjacent to the lone pair (capped face) are longer than the three furthest from the lone pair (uncapped face). Inter-ligand angles between the longer bonds are greater than those between the shorter bonds
Thionation of mesoionics with isothiocyanates: evidence supporting a four-step domino process and ruling out a [2+2] mechanism
No full textMesoionic heterocycles derived from 1,3-thiazolium-4-olates (thioisomunchnones) undergo thionation with aryl isothiocyanates to afford the corresponding 4-thiolate derivatives. Here, we document this transformation in detail, giving a crystallographic characterization of the solid-state structures. From the mechanistic viewpoint, the formal thionation process could be consistent with a [2 + 2] reaction of the exocyclic C-O bond of the thioisomunchnone with the C=S double bond of the isothiocyanate moiety, which would be competing with a (3 + 2) process as usual in mesoionic rings. Theoretical computations at the [B3LYP/6-31G(d):PM3] level, in which only bond-forming and bond-breaking reactions and neighboring atoms are treated at the DFT level, do reproduce the experimental results and rule out the expected pathway. Calculations instead suggest the existence of a four-step domino pathway through several polar intermediates that agrees with the electronic nature of the substituents involved. The mechanistic hypothesis has further been corroborated by an experiment with isotopically C-13-labeled PhNCS that unambiguously shows the way in which the exchange reaction occurs
Dimeric supramolecular motifs of two carboxylate-guanidinium compounds
No full textThe structures of N-benzyl-N'-{6-[(4 carboxylatobenzyl)aminocarbonyl]-2-pyridylmethyl}guanidinium, C23H23N5O3, (I), and N-[2-(benzylaminocarbonyl)ethyl]-N'-{6-[(4-carboxylatobenzyl)aminocarbonyl]-2-pyridylmethyl}guanidinium monohydrate, C26H28N6O4·H2O, (II), both form three-dimensional supramolecular hydrogen-bonded networks based on a dimeric primary synthon involving carboxylate-guanidinium linkages. The differences in the geometries and hydrogen-bonding connectivities are driven by the additional methylpropionamide group and water of crystallization of (II
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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