0000000000059945
AUTHOR
Roland Fröhlich
Synthesis, reactions and structural features of monofluorinated cyclopropanecarboxylates
Abstract Monofluorinated cyclopropanecarboxylates are available in racemic or optically active form by transition metal-catalyzed reactions of vinylfluorides with diazoacetates. From α-fluorostyrene and tert-butyl diazoacetate in the presence of 2 mol% of an enantiopure bis(oxazoline) copper complex, a 81:19 mixture of tert-butyl trans- and cis-2-fluoro-2-phenylcyclopropanecarboxylates was obtained with high enantiomeric excess (ee) of 93 or 89%, respectively. The corresponding racemic ethylesters were used as starting materials for the synthesis of carboxamides, of the cis- and trans-isomers of analogues of tranylcypromine, an anti-depressive drug and several of its homologous fluorinated …
Zirconocene complexes bearing novel 3-dimethylamino-1,2-dihydropentalene derived ligand systems.
Coupling of the N,N-dimethylacrylamides 6a-c with cyclopentadienide resulted in the formation of the substituted 3-dimethylamino-1,2-dihydropentalnenes 2a-c. Deprotonation followed by metallation with CpZrCl(3)·DME gave the substituted zirconocenes 12a-c. The reaction of 3-dimethylamino-1-methyl-dihydropentalene 2a with ZrCl(2)(NMe(2))(2)·2THF resulted in a unique coupling between a pair of the aminodihydropentalene derivatives to yield an unsymmetrically bridged novel ansa-zirconocene framework (9a). Treatment of the 1,1-dimethyl-substituted substrate 2b with this Zr-amido reagent in contrast resulted in a clean deprotonation and formation of the unbridged bis(dimethylaminohydropentalenyl)…
Crystal Structures and Thermal Behavior of Bis(dibenzyldimethylammonium) Tetrabromometallates(II) [M = Mn(II), Co(II) and Zn(II)] and Their Solvates
Six new A2MBr4 structures [A = dibenzyldimethylammonium cation,M = Mn(II), Co(II) or Zn(II)] were crystallized with or without solvent molecules from acetonitrile, methanol and/or aqueous solutions. The isomorphous compounds [(Bz2Me2N)2][MnBr4]·CH3CN·H2O (1) and [(Bz2Me2N)2]-[ZnBr4]·CH3CN·H2O (4) crystallize in the triclinic space group P1̄ from acetonitrile solutions. The solvent molecules participate in the hydrogen bonding network inside the crystal structure. [(Bz2Me2N)2][CoBr4]·0.5CH3CN (2) crystallizes from an acetonitrile solution in the monoclinic space group P21/c. The solvent molecules fill the voids of the crystal structure. Compound 2 is isostructural with the previously reporte…
Asymmetric Homoaldol Reactions with Cyclohex-2-enylN,N-Diisopropylcarbamate: Kinetic Resolution, Elucidation of the Stereochemical Course and Applications in the Synthesis of Hexahydroisobenzofuran-4-(1H)-ones
Enantio-enriched cyclohex-2-enyl N,N-diisopropylcarbamate (5) is stereospecifically deprotonated by sec-butyllithium/(–)-sparteine (9) to form the configurationally stable lithium complex 7·9. A kinetic resolution of rac-5 by n-butyllithium/(–)-sparteine (9) yielded (R)-5 with up to 99 % ee. Electrophilic substitution with tin electrophiles proceeds in a anti-SE′ fashion as shown by chemical correlations. The synthesized allylstannanes 10 undergo a highly stereospecific TiCl4-mediated homoaldol reaction with various aldehydes, yielding syn-configured homoaldol products 12. These were transferred into all-cis-configured hexahydroisobenzofuran-4(1H)-ones 22 by BF3·OEt2-mediated reactions with…
Hierarchical, Lithium‐Templated Assembly of Helicate‐Type Complexes: How Versatile Is This Reaction?
Catechol ligands that bear carbonyl functions such as esters or aldehydes in the 3-position (1a–c-H2) form triple-stranded, helicate-type complexes [Li3(1a–c)6Ti2]– with titanium(IV) and the corresponding double-stranded compounds [Li2(1a–c)4B2] with boron(III) in hierarchical, lithium-templatedprocesses. The related 8-hydroxyquinoline ligands 2a,b-H can be used for the formation of similar complexes[Li3(2a,b)6M2]+ with cobalt(II), nickel(II), or zinc(II). A prerequisite for the formation of the lithium-bridged dimers is a negative charge of the mononuclear complexes, which are able to electrostatically attract the lithium cations and thus compensate the repulsion between the cations. (© Wi…
The role of cation⋯π interactions in capsule formation: co-crystals of resorcinarenes and alkyl ammonium salts
An unprecented dimeric capsular assembly of a tetramethylated C-hexyl resorcinarene and an expected one from unsubstituted C-butyl resorcinarene with tetramethylammonium cation are described. Surprisingly tetramethylated C-hexyl resorcinarene, with no apparent possibility for intra-capsular hydrogen bonds, forms a capsule which is held together solely by the cation⋯π interactions and the complementary geometry of the spherical guest cation and the concave resorcinarene host. The C-butyl resorcinarene capsule, as in the case of dimeric resorcinarene capsules reported earlier, is mediated viasolvent molecules and intra-capsular hydrogen bonds. We also report here two co-crystals of C-methyl r…
Versatile behavior of conjugated diynes with zirconocene reactive species
Thermal decomposition of Cp2ZrPh2 in the presence of the buta-1,3-diynes RC≡CC≡CR (R = Ph, SiMe3) can lead to seven- or five-membered metallacycles. In both cases a stable benzo-fused seven-membered zirconacyclocumulene arising from a 2-fold insertion of the triple bonds of the dialkyne in the in situ generated zirconocene benzyne is formed. In the case of Me3SiC≡CC≡CSiMe3 a second minor complex is isolated: a 3-alkynyl-substituted zirconaindene arising from a β monoinsertion of one acetylenic function of the conjugated diyne in the zirconocene benzyne. No stable 2-alkynyl-substituted zirconacycle was isolated. This α monoinsertion complex is an intermediate in the exchange of the metalated…
Zinc(II) complexes of amide- and urea-substituted 8-hydroxyquinolines
Abstract A series of amide- and urea-substituted 8-hydroxyquinoline ligands 1–6-H are used for the formation of zinc(II) complexes. Hereby in general 2:1 complexes are obtained and the X-ray structure of [(3)2Zn] reveals the presence of a coordination polymer in the solid state. Only the derivatives of 7-amino-8-hydroxyquinoline 4-H and 5-H form trinuclear hexa-helical 6:3 complexes which exhibit interesting structural and NMR and fluorescence spectroscopic properties.
Synthesis and X-ray structure of amide-based macrocycles, catenanes and pretzelane
The syntheses and crystal structure studies of amide-based catenanes derived from m-phenylene diacrylic acid and 5-acetoxy isophthalic acid (17% and 3% yield of 4a and 4b resp.) and octalactam macrocycles (21% yield of 3) are described. Hydrogen bonding patterns play a key role in the formation of the different conformations of octalactam 3. The crystal structures of 3 reveal a number of hydrogen-bonding interactions between the macrocycle and two different solvent molecules, which are presumably responsible for the different conformations. Furthermore, we report the X-ray structure of a catenane, which was converted into a “pretzelane” by bridging two phenolic hydroxy groups with a p-xylyl…
Shedding Light on the Interactions of Hydrocarbon Ester Substituents upon Formation of Dimeric Titanium(IV) Triscatecholates in DMSO Solution
Abstract The dissociation of hierarchically formed dimeric triple lithium bridged triscatecholate titanium(IV) helicates with hydrocarbyl esters as side groups is systematically investigated in DMSO. Primary alkyl, alkenyl, alkynyl as well as benzyl esters are studied in order to minimize steric effects close to the helicate core. The 1H NMR dimerization constants for the monomer–dimer equilibrium show some solvent dependent influence of the side chains on the dimer stability. In the dimer, the ability of the hydrocarbyl ester groups to aggregate minimizes their contacts with the solvent molecules. Due to this, most solvophobic alkyl groups show the highest dimerization tendency followed by…
Molybdenum Pentachloride Mediated Synthesis of Spirocyclic Compounds by Intramolecular Oxidative Coupling
The oxidative treatment of (m)ethyl 2-aryl cinnamates equipped with methoxy groups in position 4 of the phenyl moiety promote the formation of cyclohexadienone substructures. This dealkylative oxidative C–C coupling gives access to spirocyclic compounds and avoids the construction of the corresponding phenanthrenes. Furthermore, the transformation can be expanded to other spirocyclic systems.
New indications for the potential involvement of C–F-bonds in hydrogen bonding
Abstract Solid state structures of a selection of 2-fluoro-2-phenylcyclopropane derivatives were examined by X-ray crystallography in order to identify short intermolecular contacts of C–F groups to H–X moieties (X=C, N). Particularly, several cis -configured fluorinated phenylcyclopropane derivatives showed extremely close intermolecular contacts. The shortest of such C–H⋯F–C-distances (2.17 A, C–F–H angle 162°) was found in (1 S ,2 R )-(2-fluoro-2-phenylcyclopropyl)methyl N -(4-bromophenyl)carbamate ( 8 ) and the closest N–H⋯F–C-interaction (2.01 A, C–F–H angle 167°) was found in (±)- cis -2-fluoro-2-phenylcyclopropyl carboxamide ( 4 ). Comparison of the structures of several of the fluor…
Crystal Structures and Thermal Behavior of Isostructural Bis(dibenzyldimethylammonium) Tetrachlorometallate [M = Mn(II), Co(II), Ni(II) and Zn(II)] Solvates Crystallized from Acetonitrile and/or Methanol Solutions
Five isostructural bis(dibenzyldimethylammonium) tetrachlorometallate solvate complexes [M = Mn(II), Co(II), Ni(II) or Zn(II)] were crystallized from acetonitrile and/or methanol solutions. The crystal structures are compared to those of the analogous, isostructural copper compounds (X = Cl or Br) reported earlier. The complexes crystallize in the monoclinic space group P21/n with Z = 4, and unit cell dimensions of a ≈ 14.1, b ≈ 16.1, c ≈ 15.7 °A and β ≈ 108 - 109°. The asymmetric unit of these compounds contains one MCl4 2− anion, two Bz2Me2N+ cations in theW-conformation and one half of a disordered solvent molecule (acetonitrile or methanol). The geometry of the MCl4 2− anion is close to…
Self-assembly of 2,8,14,20-tetraisobutyl-5,11,17,23-tetrahydroxyresorc[4]arene
We report herein the observation of a hexameric structure of a hydroxyresorc[4]arene in the solid state, enclosing a large interior space. This artificial molecular container is stabilized only by hydrogen bonds. The tendency to form aggregates in solution is demonstrated mainly by means of ESI-MS methods.
Synthesis of a tetradentate piperazine ligand and a structural study of its coordination compounds
Abstract A tetradentate ligand N,N′-bis(2-pyridylmethyl)piperazine (L1) and seven structures of its transition metal coordination compounds are described. Most of the compounds are of the general formula [M(L1)(NO3)2], with M=Cu2+, Co2+, Mn2+and Cd2+. In addition, a dimeric copper(II) compound, [Cu2(L1)(Ac)4](H2O)3, and polymeric silver(I) compounds, [Ag(L1)]n(NO3)n(EtOH)n and [Ag(L1)]n(SO3CF3)n, were formed. The overall structure of L1 in the metal complexes A–G varies with the size and electronic properties of the metal ions. Mononuclear complex A is a five-coordinated, B is a six-coordinated, and C and D are eight-coordinated metal complexes. The dinuclear Cu complex, E, is four-coordina…
CCDC 1415863: Experimental Crystal Structure Determination
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CCDC 1950786: Experimental Crystal Structure Determination
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CCDC 1919187: Experimental Crystal Structure Determination
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CCDC 1917460: Experimental Crystal Structure Determination
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CCDC 1415860: Experimental Crystal Structure Determination
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CCDC 1415861: Experimental Crystal Structure Determination
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CCDC 1427184: Experimental Crystal Structure Determination
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CCDC 1919188: Experimental Crystal Structure Determination
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CCDC 1919186: Experimental Crystal Structure Determination
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CCDC 1917415: Experimental Crystal Structure Determination
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CCDC 1415862: Experimental Crystal Structure Determination
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CCDC 1427185: Experimental Crystal Structure Determination
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CCDC 1419863: Experimental Crystal Structure Determination
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