bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation, Structure and Optical Properties of [CH3SC(NH2)2]3SnI5, [CH3SC(NH2)2][HSC(NH2)2]SnBr4, (CH3C5H4NCH3)PbBr3, and [C6H5CH2SC(NH2)2]4Pb3I10
Authors: Raptopoulou C. P. , Terzis A. , Mousdis G. A. , Papavassiliou G. C. 
Published: August 2018

Abstract
The preparation, crystal structure and optical absorption spectra of [CH3SC(NH2)2]3SnI5 (1), [CH3SC(NH2)2][HSC(NH2)2]SnBr4 (2), (CH3C5H4NCH3)PbBr3 (3), and [C6H5CH2SC-(NH2)2]4Pb3I10 (4) are reported. The compounds 1, 2, 3 consist of MX6-octahedra (M = Sn, Pb, X = I, Br) forming one-dimensional single chains (compounds 1, 3) or double chains (compound 2). The compound 4 forms a two-dimensional inorganic network via corner sharing of three face sharing octahedral units. Because of their low-dimensional character, a blue shift of the excitonic absorption bands, in comparison to those of higher dimensionality systems, is observed.
A New Trinuclear Cyano-Bridged Sr-Fe(III) Complex, [Sr2(phen)4(H2O)3(NO3)Fe(CN)6] · H2O
Authors: Datta Amitabha , Karan Nirmal Kumar , Mitra Samiran , Malik K. M. Abdul 
Published: August 2018

1
A new cyano-bridged trinuclear complex [Sr2(phen)4(H2O)3(NO3)Fe(CN)6] · 1.25 H2O () (where phen = 1,10-phenanthroline) has been synthesised and its crystal structure determined. The structure features a central [Fe(CN)6]3- unit that links a [Sr(phen)2(OH2)2]2+ dication and a [Sr(phen)2(OH2)(NO3)]+ monocation via two trans cyanide bridges. In the dicationic part, the Sr centre achieves a pentagonal bipyramidal geometry whereas in the monocationic part, the Sr centre shows a square antiprismatic geometry. The presence of an extensive network of hydrogen bonds imparts the overall stability to the system.
Transition Metal-Gallium Ordering In HfCoGa2 And HfNiGa2
Authors: Schlüter Martin , Heying Birgit , Pöttgen Rainer 
Published: August 2018

Abstract
The gallides HfCoGa2 and HfNiGa2 were synthesized by arc-melting of the elements and subsequent annealing in glassy carbon crucibles. Their structures have been reinvestigated by X-ray diffraction on powders and single crystals: I4mm, a = 1222.4(1), c = 812.0(1) pm, wR2 = 0.0766, 1464 F2 values, 64 variables, BASF = 0.41(2) for HfCoGa2 and a = 1224.0(2), c = 809.3(2) pm, wR2 = 0.0609, 1499 F2 values, 63 variables for HfNiGa2. In contrast to a previous investigation (Dopov. Akad. Nauk Ukr. RSR, Ser. A, 51 (1988)) we observe a fully ordered arrangement of the transition metal and gallium atoms. The crystal chemistry of these gallides is briefly discussed.
Hydroxyurea Analogues of Fosmidomycin
Authors: Kurz Thomas , Geffken Detlef , Wackendorff Claudia 
Published: August 2018

Abstract
Benzyloxyureas (4) have been prepared by reactions of diethyl 3-benzyloxyamino-propyl-phosphonate (3) with isocyanates, potassium cyanate or 1,1’-carbonyldiimidazole / methylamine. Conversion of phosphonic esters 4 into phosphonic acids 6 by means of bromotrimethylsilane and catalytic hydrogenation of 4, 6 afforded the target compounds 5, 7.
Novel Asymmetrical Dianionic Polyimido-Sulfur(IV)-Ylides
Authors: Selinka Carola , Stalke Dietmar 
Published: August 2018

Sulfurdiimides RN=S=NR react in donating solvents with two equivalents of lithiumalkyls to give the dimeric C,N-dilithium-methylenediimidosulfite solvent adducts [(Et2O)Li2{H2CS-(NSiMe3)(NtBu)}]2 (1) and [(thf)Li2{H8C4S(NtBu)2}]2 (2). Firstly, addition of a lithiumalkyl to sulfurdiimide gives the diimidosulfinates [RS(NR')2]- (1: R = Me, R′ = tBu, SiMe3; 2: R = nBu; R′ = tBu) while in a second step the α-carbon atom in R is metalated with one equivalent of lithiumalkyl to give the asymmetric S-ylides. The reaction of 3-bromothiophene with one equivalent of nBuLi and one of sulfurdiimide tBuN=S=NtBu resulted in the dilithium-3-thiophenylenediimidosulfite [(thf)Li2{(SC4H2)S(NtBu)2}]2 (3). It can be regarded
as the first example of a dianionic S(IV)-β-ylide. This class of compounds can be rationalised as sulfite analogues, where two oxygen atoms are isoelectronically replaced by a NR group each and the remaining oxygen atom is replaced by a CR2 group. The rich coordination chemistry of the triimidosulfites is extended by the introduction of a hard carbanionic centre.
(1,2-DAPH2)2Ge9(OH)4O18 · 2H2O: A New Microporous Germanate Based on the Interconnection of Ge9O18 Clusters Showing Reversible Water Emission and Uptake
Authors: Pitzschke Dragan , Näther Christian , Bensch Wolfgang 
Published: August 2018

Treatment of germanium dioxide with a 33% aqueous solution of 1,2-diaminopropane (DAP) under solvothermal conditions leads to the formation of colourless octahedral crystals of the novel germanate (1,2-DAPH2)2Ge9(OH)4O18 · 2 H2O. The compound crystallises in the orthorhombic space group Pbca, a = 14.4155(10), b = 12.9384(9), c = 14.5417(8) Å,V =2712.2 (3) Å3; Z =4. The structure consists of an anionic [Ge9(OH)4O18]4− framework with isolated [1,2-DAPH2]2+ cations and water molecules in the channels of the structure. The primary building units of the anionic framework are GeO4 tetrahedra, GeO5 trigonal bipyramids, and GeO6 octahedra. The asymmetric unit consists of two GeO5 units sharing a common edge to form a Ge2O8 unit. This Ge2O8 unit is corner-linked to two GeO4 tetrahedra, and finally one GeO4 tetrahedron is connected to a GeO6 octahedron by cornersharing. The connectivity yields a chain-like Ge5O19 fragment as a secondary building unit (SBU). The chain fragments are interconnected with each other forming the three-dimensional framework. Three types of channels with diameters ranging from 5.98 to 8.025 Å intersect the three-dimensional germanate network. Upon heating the compound decomposes in three steps starting at about 125˚C losing the water and the 1,2-diaminopropane molecules.
In situ X-ray diffraction experiments show that the water molecules are removed retaining the integrity of the skeleton of the material. The removal of H2O is accompanied with an anisotropic shrinkage of the structure. The original lattice parameters were obtained after the uptake of water.
Calculated NMR Parameters (Chemical Shifts and Coupling Constants) of Cyclic C4H2 and C4H4 Molecules Containing Carbene Centers, and of Some of their Boron Analoga, Using Density Functional Theory (DFT)
Authors: Wrackmeyer Bernd 
Published: August 2018

Abstract
Singlet state structures of small, cyclic hydrocarbons which can result from the addition of molecular dicarbon (C2) to ethyne (HC≡CH) or ethene (H2C=CH2) have been calculated (B3LYP/6- 311+G(d,p) level of theory), and were found to contain carbene centres. Some structures of analogous boranes (replacement of the carbene centers by BH fragments) were also calculated. The computation of NMR parameters such as chemical shifts δ 13C and δ 11B, and coupling constants 1J(13C,1H), 1J(11B,1H), J(13C,13C) and J(13C,11B) shows that these data can be used for the discussion of the bonding situation. The presence of inverted carbene centers is clearly indicated by the increased 13C nuclear magnetic shielding. Scalar 13C-13C spin-spin coupling involving carbene centers are frequently dominated by spin-dipole and spin-orbital interactions.
A New Triterpenoid Saponin from Ononis spinosa and Two New Flavonoid Glycosides from Ononis vaginalis
Authors: Shaker Kamel H. , Dockendorff Katja , Bernhardt Mirko , Seifert Karlheinz 
Published: August 2018

Abstract
The new triterpenoid saponin 3-O-[α-L-rhamnopyranosyl-(1→2)-β -D-xylopyranosyl-(1→2)- β -D-glucuronopyranosyl]-3β ,22α-dihydroxyolean-13-en-11-one has been isolated from Ononis spinosa. The new flavonoid glycoside 3-O-[2-O-(E)-p-coumaroyl-β -D-galactopyranosyl]-7-O-β - D-glucopyranosylkaempferol and the new pterocarpan glucoside 3,4-di-O-β -D-glucopyranosyl-4- hydroxymedicarpin have been obtained from Ononis vaginalis. The structures were determined primarily by NMR spectroscopy. The assignment of NMR signals was performed by means of 1H-1H COSY, ROESY, TOCSY, HMQC HMQC-COSY and HMBC experiments.
Die Synthese von 2-Methyl-5-phenacyl-1,3,4-thiadiazolen / The Synthesis of 2-Methyl-5-phenacyl-1,3,4-thiadiazoles
Authors: Kantlehner Willi , Haug Erwin , Kinzy Willy , Scherr Oliver , Ivanov Ivo C. 
Published: August 2018

Keywords
2,5-Dimethyl-1,3,4-thiadiazole (1a) reacts which aromatic carboxylic acid esters 8a - u in the presence of excessive sodium hydride under condensation to give sodium enolates which afford on hydrolysis the phenacyl-1,3,4-thiadiazoles 9a - u. The action of aromatic carboxylic acid chlorides on 1a in the presence of triethylamine gives rise to the formation of mixtures of diacylated thiadiazole derivatives 16 and 18. In some cases the pure 3-acyl-phenacylidene-2,3-dihydro-1,3,4-thiadiazoles 16 can be isolated. Generally the compounds 16 are rearranged on heating in higher boiling solvents to give the enolbenzoates 18. Hydrolysis of the diacylated thiadiazoles 16 and 18 yields the phenacylthiadiazoles 9a, c, d, g - j, v, w.
Reactions of Quinolizine- and Pyridino[1,2–a]pyrimidine-3-diazonium Tetrafluoroborates with Aliphatic Amines
Authors: Rečnik Simon , Svete Jurij , Stanovnik Branko 
Published: August 2018

Keywords
Reactions of 1-cyano-4-oxo-4H-quinolizine-3-diazonium tetrafluoroborate (1a) and 4-oxo-4Hpyridino[ 1,2-a]pyrimidine-3-diazonium tetrafluoroborate (1b) with aliphatic amines 2a - g were studied. Treatment of heteroaryldiazonium salts 1 with secondary amines 2a - d afforded the corresponding N-alkyl-N’-heteroaryltriazenes 3a - h in high yields. On the other hand, reactions of 1a with aliphatic primary amines 2e - g resulted in an unexpected rearrangements into the corresponding picolinic acid N-alkylcarboxamides 4a - c.
Magnetic Properties and Crystal Structure of a CuIIGdIII Heterodinuclear Schiff Base Complex
Authors: Elmali Ayhan , Elerman Yalçın 
Published: August 2018

Abstract
The crystal structure and the magnetic properties of a heterodinuclear complex, [LCu(Me2CO)Gd(NO3)3]2 (L=N,N’-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane) are reported: [(C19H20N2O4)Cu(C3H6O)Gd(NO3)3]2, triclinic, space group P1, with a = 12.118.3(9), b = 13.562(3), c = 9.391(3) Å , α = 93.03(3), β = 107.65(2), γ = 73.07(2)°, V = 1406.0(7) Å3, Z = 1. The crystal structure consists of two independent binuclear CuIIGdIII complexes and two non-coordinating acetone molecules in the asymmetric unit. The central region of the complexs is occupied by CuII and GdIII ions which are bridged by two phenolato oxygen atoms of the ligand. The CuII ion is in a square-planar geometry and coordinated by four donor atoms of the ligand (N2O2). The GdIII ion is deca-coordinated. In addition to the two phenolate oxygen atoms, its coordination sphere contains two oxygen atoms of the OMe side arms of L and six oxygen atoms from the three bidentate nitrate ions. The average Cu···Gd separation is 3.375(2) Å . The χT versus T plots, χ being the molar magnetic susceptibility per CuIIGdIII unit and T the temperature, has been measured in the 4 - 347 K range. The values of the intrachain interaction parameters have been deduced from the magnetic data: J = 7.4 cm−1, gCu = 2.12, gGd = 2.06. This indicates a weak ferromagnetic spin exchange interaction between CuII and GdIII ions. The nature of the magnetic super-exchange interaction of the title compound is compared with similar CuIIGdIII heterodinuclear complexes.
Kristallzucht und Strukturaufklärung von K2[Pt(CN)4Cl2], K2[Pt(CN)4Br2], K2[Pt(CN)4I2] und K2[Pt(CN)4Cl2] · 2H2O/ Crystal Growth and Crystal Structure Determination of K2[Pt(CN)4Cl2], K2[Pt(CN)4Br2], K2[Pt(CN)4I2] and K2[Pt(CN)4]Cl2] · 2H2O
Authors: Mühle Claus , Karpov Andrey , Nuss Jürgen , Jansen Martin 
Published: August 2018

Abstract
Crystals of K2Pt(CN)4Br2, K2Pt(CN)4I2 and K2Pt(CN)4Cl2 ·2H2O were grown, and their crystal structures have been determined from single crystal data. The structure of K2Pt(CN)4Cl2 has been determined and refined from X-ray powder data. All compounds crystallize monoclinicly (P21/c; Z = 2), and K2Pt(CN)4X2 with X = Cl, Br, I are isostructural. K2Pt(CN)4Cl2: a = 708.48(2); b = 903.28(3); c = 853.13(3) pm; β = 106.370(2)°; Rp = 0.064 (N(hkl) = 423). K2Pt(CN)4Br2: a = 716.0(1); b = 899.1(1); c = 867.9(1) pm; β = 106.85(1)°; R(F)N′ = 0.026 (N’(hkl) = 3757). K2Pt(CN)4I2: a = 724.8(1); b = 914.5(1); c = 892.1(1) pm; β = 107.56(1)°; R(F)N′ = 0.025 (N’(hkl) = 2197). K2Pt(CN)4Cl2 ·2H2O: a = 763.76(4); b = 1143.05(6); c = 789.06(4) pm; β = 105.18(1)°; R(F)N′ = 0.021 (N’(hkl) = 2281). Raman and infrared spectroscopy data are reported.
Enzyme Inhibiting Terpenoids from Amberboa ramosa
Authors: Khan Sher B. , Malik Abdul , Afza Nighat , Jahan Nusrat , Haq Azhar U. , Ahmed Zaheer , Nawaz Sarfraz A. , Choudhary Mohammed Iqbal 
Published: August 2018

Abstract
Two new cycloartane type triterpenes 1 and 2 have been isolated from Amberboa ramosa. Their structures were established as (22R)-cycloart-20, 25-dien-2α,3β ,22α-triol 1 and (22R)-cycloart-23- ene-3β ,22α, 25-triol 2 through spectroscopic studies including 2D-NMR. The known compounds 3,4-epoxyguaia-1(10), 11(13)-dien-6, 12-olide 3, and 5-hydroxy 7,8,2’,3’-tetramethoxyflavone 4 are also reported for the first time from this species. The compounds 1 and 2 displayed inhibitory potential against butyrylcholinesterase.
Oxotellurate(IV) der Lanthanide: I. Die isotype Reihe M2Te4O11 (M = La – Nd, Sm – Yb)
Authors: Meier Steffen F. , Schleid Thomas 
Published: August 2018

Abstract
The present work is the first comprehensive account of the knowledge acquired from single crystals of the isotopic series M2Te4O11 (M = La - Nd, Sm - Yb). In the crystal structure, the M3+ cation is coordinated by eight oxygen atoms in the shape of a distorted square antiprism. Out of these polyhedra a mesh-like [M2O16]14− layer parallel to the (001) plane is built via three common edges. The [Te4O11]6− double layers in turn build two tellurium-oxygen chains crosswise to each other. The construction of the tellurium-oxygen partial structure is, however, only possible taking the secondary Te-O contacts into consideration. In most oxotellurates(IV), three oxygen atoms are covalently bound to the Te atoms (d(Te-O) ≈ 180−200 pm; ψ1 tetrahedron). Another oxygen atom is found in the near vicinity at a distance of 230 to 280 pm. The significance of such secondary interactions for the stability of the crystal structures was recognized recently in theoretical as well as experimental investigations. All oxygen atoms with distances smaller than 280 pm are counted to the secondary coordination sphere. This limit may seem somewhat arbitrary but it accounts very well for the Te-O partial structure. The coordination sphere for the tellurium center is a ψ1 trigonal bipyramid including the stereochemically active electron pair (“lone pair”). A description of the crystal structure is also possible without this partial structure, however in the [TeO3+1]4− polyhedra above and below the meshes of [M2O10]14− layers are linked via Te2-O6-Te2 contacts only.
Isolation, Characterization and Crystal Structure of Natural Eremophilenolide from Ligularia sagitta
Authors: Li Lyi , Xu Li-Wen , Jiang Yan-Feng , Xi Chan-Juan , Wang Han-Qing , Suo You-Rui 
Published: August 2018

Abstract
A new eremophilenolide 1β ,10β -epoxy-6β -acetoxy-3β -angeloyloxy-8β -hydrox y-eremophil- 7(11)-en-8,12α-olide (1), together with liguhodgsonal (2), esculetin (3) and β -sitosterol (4), was isolated from the aerial parts of Ligularia sagitta. The structure of the new constituent (1) was elucidated by spectroscopic methods and confirmed by single-crystal X-ray diffraction.
Pyrrole Thioaldehyde Complexes of Nickel, Palladium and Platinum
Authors: Pogorzeleca Peter J. , Reid David H. , Tocher Derek A. , Wilton-Ely James D. E. T. 
Published: August 2018

Abstract
The coordination chemistry of the unusual, pyrrole-stabilised thioaldehyde molecules, 3,5-dimethylpyrrole-2-carbothioaldehyde (HSPyMeHMe) and 3,5-dimethyl-4-ethylpyrrole-2-carbothioaldehyde (HSPyMeEtMe) has been investigated with nickel, palladium and platinum in the complexes [M(κ2- SPyMeRMe)2] (M = Ni, Pd, Pt; R = H, Et). The structure of the cyclometallated derivative [Pd(η2- C,N-C6H4CH2NMe2)(κ2-SPyMeEtMe)] was determined by X-ray diffraction.
N-Aryl Anions: Half Way between Amides and Carbanions
Authors: von Bülow Rixa , Deuerlein Stephan , Stey Thomas , Herbst-Irmer Regine , Gornitzka Heinz , Stalke Dietmar 
Published: August 2018

Abstract
A ‘carbanion’ can coordinate to a metal like an ‘amide’ if there is a nitrogen atom present to withdraw electron density from the formally negatively charged carbon center. On the other hand, shifting the negative charge from the amido nitrogen atom to the carbon substituent should convert an ‘amidic’ into a ‘carbanionic’ coordination behavior. This seems feasible with various substituents at the aromatic ring in a primary amide. This paper is concerned with the influence of aromatic substitution, as well as with the nature of the metal ion on the coordination mode of an amide ligand. Discussed are the parent lithium anilide [(thf)2LiNH(C6H5)]2 (1), the pentafluorinated lithium anilide [(thf)2LiNH(C6F5)]2 (2) and the lithium amino benzonitrile [(thf)2LiNH(C6H4
pCN)]2 (3). All amide ligands coordinate the lithium cation exclusively with their amido nitrogen atom. In the dimeric structure of 1 the atom can be regarded to be sp2-hybridized. Fluorine substitution of the ring results in a slightly more pronounced coupling of the negative charge to the aromatic ring. A para-nitrile group further enhances quinoidal perturbation of the C6-perimeter from six-fold symmetry. Consequently, the ipso- and ortho-carbon atoms of the ring are partially negative charged. Those carbon atoms are only attractive for the soft rubidium cation in an aza allylic coordination in [(thf)2RbNH(C6H4
pCN)]n (4) but not to the hard lithium cation.
Oxidative Addition of Methyl Iodide to Dinuclear Gold(I) Amidinate Complex: Schmidbaur’s Breakthrough Reaction Revisited with Amidinates
Authors: Abdou Hanan E. , Mohamed Ahmed A. , Fackler John P. 
Published: August 2018

Abstract
Oxidative-addition of methyl iodide, CH3I, to the dinuclear gold amidinate [Au2(o-Me2-form)2] in THF generates a metal-metal bonded Au(II) product, formulated as [Au2(o-Me2-form)2CH3I], in quantitative yield under nitrogen at 0 °C and in absence of light. The product is characterized by 1H NMR, elemental analysis and preliminary X-ray crystallography.
(EtZn)4Zn2(PSitBu3)4 – a Homometallic Phosphanediide of Zinc with a Novel Zn6P4 Cage
Authors: Westerhausen Matthias , Sapelza Gerhard , Zabel Manfred , Pfitzner Arno 
Published: August 2018

Abstract
The metalation of tri(tert-butyl)silylphosphane with diethylzinc yields quantitatively the title compound tetraethyltetrakis(tri(tert-butyl)silylphosphanediido)hexazinc (1) with a novel Zn6P4 cage with two Zn2P2 rings interconnected by two zinc atoms.
The Zinc Aqua Complex of a Tetrapodal Pentaamine Ligand and its Reactivity towards Carbon Dioxide
Authors: Pitarch López Jesús , Heinemann Frank W. , Grohmann Andreas 
Published: August 2018

Abstract
In the context of derivatisation studies of the pentaamine ligand 2,6-C5H3N[CMe(CH2NH2)2]2 (2-(6-(1,3-diamino-2-methylpropan-2-yl)pyridin-2-yl)-2-methylpropane-1,3-diamine, 1), we explored its zinc(II) coordination chemistry. With ZnBr2 in hot aqueous ethanol, in the absence of Lewis acid, the aqua complex [Zn(1)(H2O)]Br2 (2) is obtained, in which the pentaamine ligand acts as a square-pyramidal coordination cap. Single crystal structure data for the dihydrate of 2 are reported. In methanol solution, the complex is reactive towards carbon dioxide, and spectroscopic data (IR, 13C NMR) indicate the reversible formation of the dinuclear methyl carbonate complex [(Zn(1))2(μ2-(η1-O,η1-O)O2COCH3)]Br3.
2′-Oxoethyl Flavin Revisited
Authors: Svoboda Jiří , König Burkhard , Sadeghian Keyarash , Schützb Martin 
Published: August 2018

The present work investigates the possibility of using 2'-oxoethyl flavin (2) as a starting material for the construction of more complicated flavin-based molecules. 2'-Oxoethyl flavin (2), prepared by oxidative degradation of commercially available riboflavin 1, is however a rather untypical aldehyde. It prefers the hydrated gem-diol form 4 in aqueous solution. Ab initio electronic structure calculations, carried out at the level of Møller-Plesset perturbation theory of second order (MP2), predict the existence of an intramolecular hydrogen bond between one of the hydroxy groups of the diol and the N1 atom of the flavin skeleton. This result is supported by 1H NMR measurements which indicate an interaction between the hydroxy groups and the conjugated ring system. We postulate that this rather strong intramolecular hydrogen bond is the origin of the enhanced stability of the gem-diol over the aldehyde form 2.
Synthetic applicability of 2'-oxoethyl flavin 2 is limited by low solubility in most organic solvents and sensitivity to basic conditions. The aldehyde functional group is surprisingly reluctant to nucleophilic attack, and several reactions quite typical for aldehydes failed. Nevertheless, reductive amination led to the expected secondary amine 7. Solubility of the molecule thus increased, and a new amino group was introduced.
1,3-Dipolar Cycloadditions of (1Z,4R*,5R*)-4-Benzamido-3-oxo- 5-phenylpyrazolidin-1-ium-2-ides to Ethyl Propiolate
Authors: Pezdirc Lidija , Stanovnik Branko , Svete Jurij 
Published: August 2018

Abstract
1,3-Dipolar cycloadditions of (1Z,4R*,5R*)-4-benzamido-3-oxo-5-phenylpyrazolidin-1-ium-2- ides 3a - e to ethyl propiolate (4) were studied. The reactions were carried out in anisole under reflux and in anisole under microwave irradiation at 150°C. All reactions were quite non-selective and furnished mixtures of isomeric cycloadducts, 5, 5′ , 6, and 6′ , with ethyl (1S*,6R*,7R*)-6-benzamido-1- (4-nitrophenyl)-5-oxo-7-phenyl-1,5,6,7-tetrahydropyrazolo[1,2-a]pyrazole-2-carboxylates 5a - e as the major isomers. Pure major isomers 5a - e were obtained in low to moderate yields upon thorough chromatographic workup (CC followed by MPLC). The structures of cycloadducts 5, 5′ , 6, and 6′ were determined by 1H NMR and NOESY spectroscopy.
Diverse Reactivities of Acetylenic Iminium Salts Toward 1,3-Oxazolium-5-olates (Münchnones)
Authors: Gerster Holger , Maas Gerhard 
Published: August 2018

Abstract
The acetylenic iminium salts [(c-C3H5)C≡C-C(Ar)=N+Me2]OTf, Ar = phenyl (1a) or 2- thienyl (1b), both react in different ways with three mesoionic münchnones, namely 3-methyl-1,3-oxazolium-5-olate (2), 3-methyl-2-phenyl-1,3-oxazolium-5-olate (6) and 3-methyl-2-phenyl-4- trifluoroacetyl-1,3-oxazolium-5-olate (9). With 2, a [3+2] cycloaddition reaction followed by extrusion of CO2 yields pyrroles 5a, b. In the case of 6, the new münchnones 7a, b are obtained which result from an electrophilic substitution at C-4 by the acetylenic iminium cation. In contrast to 1a, b, the 4,4-but-2-yne 1-iminium salt 1c reacts with münchnone 6 to form pyrrole 8. Finally, the reaction of 1a, b and 9 affords (6-oxo-6H-pyran-3-yl)methylene iminium salts 10a, b under microwave heating conditions. The structures of pyrrole 5a, münchnone 7a, and trifluoromethyl-substituted pyranone 10a were established by single-crystal X-ray diffraction analysis.