Search

Tandem Knoevenagel-Michael addition of diethyl malonate to nitro-substituted benzaldehydes was found to proceed in a mild and convenient process. The H-1 NMR spectra of the products showed significant changes according to the position of the nitro group. Conformational analysis calculations confirmed that in all cases, a structure containing a mirror plane occurred at energies near the ground state. However, for the meta and ortho substituted products, increased steric crowding resulted in decreased rotational freedom of the ethyl substituents. Consistent with the observation of increased steric stress, molecular orbital calculations predicted a higher electrophilic reactivity of the ortho nitro substituted product. (C) 2022 Elsevier B.V. All rights reserved.

EgeUn###, Two novel copper(II) complexes, Cu2L2(bipy) and Cu2L2(H2O)(4)3H(2)O of Schiff base ligands derived from the condensation of L-tert-leucine and L-isoleucine with 2,4-dihydroxybenzaldehyde, are synthesized and characterized by single crystal X-ray diffraction. Compounds crystallize in the orthorhombic crystal system. The Cu2L2(bipy) complex has a distorted square planar geometry with an N2O2 coordination environment. Water is contained in supramolecular network pores. On the other hand, in the Cu2L2(H2O)(4)3H(2)O complex, both copper atoms adopt a five-coordinated distorted square-pyramidal geometry with an NO4 coordination environment and guest water molecules form a 1D water chain. Both complexes build a 2D supramolecular network., Dokuz Eylul UniversityDokuz Eylul University [2010.KB.FEN.13], We acknowledge Dokuz Eylul University for the use of the Agilent Xcalibur Eos diffractometer (purchased under University Research Grant No: 2010.KB.FEN.13).

WOS: 000403692800006, Four new chiral Schiff base ligands (3a-4a, 3b-4b) have been prepared using aminoisopropylidene derivatives of glucose and aminochloralose derivatives of mannose. The synthesized compounds 1 and 2 were characterized by nuclear magnetic resonance (H-1 and C-13 NMR), Fourier transform infrared spectroscopy (FTIR), UV/visible spectroscopy, and elemental analysis. A total of eight Schiff base compounds (3a-6a, 3b-6b) were tested for antimicrobial activity against Escherichia coli ATCC 12228, Staphylococcus aureus ATCC 6538, Klebsiella pneumoniae CCM 2318, Pseudomonas aeruginosa ATCC 27853, Salmonella typhimurium CCM 5445, Enterococcus faecalis ATCC 29212, Bacillus subtilis ATCC 6633, and Candida albicans ATCC 10239 and exhibited a range of activities.

Cycloheptatrienyl-bridged RuRh and RuIr pentacarbonyl complexes were found to undergo metal–carbon and carbon–carbon bond-forming reactions with hexafluoro-2-butyne to afford products in which coupling of the alkyne and cycloheptatrienyl group had occurred. Reaction of the RuRh complex occurred readily at room temperature whereas the RuIr complex required thermal activation of 100 °C, which resulted in incorporation of two alkyne units into the product.

Ozdemir, Namik/0000-0003-3371-9874; KOZ, GAMZE/0000-0003-3276-1413 WOS: 000275769700007 The title complex, trans-diaqua{5,5'-[(E,E)-pyridine-2,6-diylbis(methylidynenitrilo)]bis-[pyrimidine-2,4 (1H,3H)-dionel)}cobalt(II) bis(hexafluorophosphate) dihydrate [Co(C15H11N7O4) (H2O)(2)]center dot 2(PF6)center dot 2(H2O), has been synthesized, and characterized by IR spectroscopy and single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2(1)/c with a = 10.7301(4) angstrom, b = 12.0537(3) angstrom, c = 21.6030(9) angstrom and beta = 109.392 (3)degrees. In the title complex, the Co2+ centre is seven-coordinated in a slightly distorted pentagonal-bipyramidal geometry, with the two water O atoms located in the apical positions, and the pyridine N atom, the two imine N atoms and two carbonyl O atoms of the uracil groups located in the equatorial plane. The positions of fluorine atoms in the hexafluorophosphate groups were disordered. The charge is balanced by two PF62- anions. In addition to the molecular geometry from X-ray experiment, theoretical studies have been carried out on the structures of the pentagonal-bipyramidal [Co(L)(H2O)(2)](2+) and [Zn(L)(H2O)(2)](2+) cations using the Hartree-Fock (HF) and density functional theory (DFT-B3LYP) methods in conjunction with effective core potential basis set (LANL2DZ) to clarify the solid state behaviour of these cations. Besides, frontier molecular orbitals (FMO) analysis and natural bond orbital (NBO) analysis of [Co(L)(H2O)(2)](2+) cation are presented here together with vibrational frequencies and gauge including atomic orbital (GIAO) H-1 and C-13 NMR chemical shift values of the pentadentate ligand calculated at HF and DFT (B3LYP) levels with 6-31G(d) basis set. (C) 2009 Elsevier B.V. All rights reserved. Research Centre of Ondokuz Mayis UniversityOndokuz Mayis University [F-461] This study was supported financially by the Research Centre of Ondokuz Mayis University (Project No.: F-461). Gamze Koz sincerely thanks TUBITAK (the Scientific and Technical Research Council of Turkey) for their bursary support.

WOS: 000351639400011, PubMed ID: 25830964, The synthesis, thermogravimetric and X-ray structure analysis of a highly unusual copper compound prepared from a chiral tridentate Schiff base ligand is reported. The title compound [CuL(H2O) 2] center dot [ CuL(H2O) 3] center dot H2O crystallizes in the orthorhombic crystal system in space group P2(1)2(1)2(1) with Z = 4. The two independent CuL(H2O)(n) complexes are present in the same unit cell, along with an uncoordinated water molecule. The five-coordinated copper(II) centre occupies a distorted square-pyramidal geometry whereas the six-coordinated copper(II) centre has a distorted octahedral geometry. The independent copper complexes and the uncoordinated water molecule are joined together with intermolecular hydrogen bonds in a two-dimensional supramolecular network which lies parallel to the ab plane., Dokuz Eylul UniversityDokuz Eylul University [2010.KB.FEN.13], This work has been completed at Dokuz Eylul University and is the subject of the forthcoming Ph.D. Thesis of Duygu Barut. The authors acknowledge Dokuz Eylul University for the use of the Agilent Xcalibur Eos diffractometer (purchased under University Research Grant No: 2010.KB.FEN.13).

Metal–halogen exchange between Ph2CuLi · LiCN and ortho-substituted aryl iodides or bromides may be used to conveniently afford substituted metallated aryls which can subsequently undergo reaction with electrophiles.

WOS: 000480363600623

Six tridentate Schiff base ligands containing tertiary butyl or benzyl substituents were prepared from chiral amino alcohols and salicylaldehyde derivatives. The ligands were employed as catalysts for the Cu(II) catalysed asymmetric Henry reaction. It was discovered that when different carboxylate salts were used instead of copper acetate as the Cu(II) salt, significant changes in the enantioselectivity of the reactions were observed. Addition of Cu(OAc)(2) to the ligand prepared from salicylaldehyde and a, a-diphenyl-tert-leucinol resulted in the formation of dark green crystals. X-ray structural analysis of these crystals showed that a square planar monomeric complex had been formed rather than the expected dimer. In the structure, the copper(II) centre is bonded to the tridentate ONO ligand and an acetate ion. There is a strong hydrogen bond between the protonated alcoholic oxygen of the Schiff base ligand and the uncoordinated acetate oxygen atom. These results, taken together, indicate that the carboxylate anion may be an important part of the active intermediate when this type of copper complex is used as a catalyst in the asymmetric Henry reaction.

Mild and efficient enantioselective Henry reactions of nitromethane with various aldehydes were catalyzed by a novel L-(+)-aspartic acid-derived Schiff base ligand in the presence of Cu(II) ions, affording the corresponding adducts in high yields (up to 96%) and enantioselectivities (up to 92% ee).

The reaction of lithium diarylcuprate(I) reagents with o-bromobenzoyl chloride has been investigated. In general, the reaction proceeds well to give synthetically useful o-bromobenzophenone derivatives as the major product. It is suggested that a minor substituent effect, whereby diarylcuprate reagents containing an ortho or meta substituent react more favourably, may be attributed to small changes in the structure of the organometallic reagent. Copyright © 2000 John Wiley & Sons, Ltd.

Experimental and theoretical evaluations have proven that very low fluorescence quantum yields of azlactones in solution are not caused by an efficient inter system crossing from S-1*(pi pi) to T*(n pi) states, but rather from solvation and steric effects, that result in non-planarity of the molecular system. High fluorescence quantum yields in the solid state are attributed to the planarity of the azlactone molecule upon packing into the crystal lattice. Supporting evidence was found upon observation of the excited state proton transfer (ESIPT) bands of fluorescence emissions of o-hydroxyarylidene derivatives. The photoinstability of azlactones in liquid states are attributed to photochemical E-Z isomerization and cleavage of the hetero ring alpha to the carbonyl group.

Cis-4a,10b-dihydrophenanthridine derivatives have been prepared in high yield via nucleophilic addition of a functionalised metalated arene to (benzene)tricarbonylmanganese(1+) hexafluorophosphate(1−) followed by reactivation, and intramolecular nucleophile addition.

A series of stable acyclic aminals derived from L-aspartic acid are synthesized and successfully applied as chiral ligands in the Cu(II)-catalyzed Henry reaction of nitromethane with various aromatic aldehydes.

4-Methyl-3-phenyl-2-thiazolidinethione was reacted with both photochemically and chemically generated singlet oxygen. Despite reaction conditions which were selected to favor oxidation of the sulfide group, both reactions afforded a single product arising solely from thiocarbonyl oxidation.

Substitution of the chloro group in 2-(2-chlorophenyl)-4,4-dimethyl-2-oxazoline to afford biaryls occurs upon reaction with either aryllithium reagents or aryl Grignard reagents. The reactions with Grignard reagents occur under similar conditions to a previously reported manganese-catalysed procedure. The reactions with lithium reagents, whilst not always affording greater yields of product than the Grignard reagents, involve much shorter reaction times and afford yields, which are comparable with those obtained from the corresponding fluoro derivative.

Several amino acids and their derivatives have been evaluated as organic catalysts for the nitroaldol reaction. It was found that when an unprotected amino group and an unprotected carboxylate group were present in the organocatalyst, both the nitroaldol reaction and subsequent elimination could occur to afford nitroalkenes from aromatic aldehydes and nitromethane. The best results were obtained by use of gamma-amino acids derived from l-glutamine. It is suggested that the amino group is important for intermediate Schiff base formation and that the free carboxylate group facilitates the elimination step.

Chiral tridentate Schiff base ligands were prepared from L-tert-Leucine and used as catalysts in the asymmetric Henry reaction in the presence of Cu(II) ions. Moderate enantiomeric excesses (up to 66%) and yields (up to 76%) of the desired b-nitroalcohols were obtained.

The regio- and enantioselective preparation of tricarbonyl(η 5 -6(S)-endo-methoxy-1(S)-ethoxycyclohexadienyl)iron(1+) hexaflourophosphate(1−) (3, R = OEt), via a biotransformation entry, is described. The optical purity of 3 (R = OEt), which is required as an intermediate for hippeastrine synthesis, was found to be > 98% e.e. by an NMR chiral shift method.

Using asymmetric Cobalt(III) salen catalysts, the ring-opening of epichlorohydrin by 2,3-dihydroxybenzal- dehyde and 2,4- dihydroxybenzaldehyde was found to occur at the phenolic groups most distant from the aldehydic group. Switching catalysts afforded a reversal in enantioselectivity. For 2,3-dihydroxybenzaldehyde and salicylaldehyde, addition of AlCl3 to the reaction mixture led to an increase in reaction rate without any decrease in product enantiopurity.

Aygun, Muhittin/0000-0001-9670-9062; Aygun, Muhittin/0000-0001-9670-9062 WOS: 000272570500010 Reaction of the tridentate Schiff base ligands obtained from 2,4-dihydroxybenzaldehyde and either L-iso-leucine or L-tert-leucine with Ni(NO3)(2) in methanol/water solution in the presence of base afforded dinickel complexes. The crystal structure of the product derived from L-tert-leucine has been determined by X-ray crystallography. The octahedrally coordinated two Ni centers were found to be bridged by a single carboxylate group in an extremely unusual non-planar fashion. A 2D supramolecular structure, constructed by infinite hydrogen-bonded complex sheets parallel to the ab-plane of the unit cell, arises from intermolecular O-H center dot center dot center dot O hydrogen bonds. (C) 2009 Elsevier B.V. All rights Ege University Faculty of ScienceEge University; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [107T778] The authors are grateful to Ege University Faculty of Science and to TUBITAK (Grant 107T778) for financial support of this work. The authors also acknowledge the Faculty of Arts and Sciences, Ondokuz Mayis University, Turkey, for the use of the Stoe IPDS-II diffractometer (purchased under Grant No. F.279 of the University Research Fund).

Ultraviolet irradiation of [Fe(η4-polyene)(CO)3] complexes [polyene = 1,3-butadiene (C4H6), cyclobutadiene (C4H4), 2,4-cyclopentadien-1-one (C4H4CO), cyclopentadiene (C5H6), 1,3-cyclohexadiene (C6H8), 1,3-cycloheptadiene (C7H10), 1,3-cyclo-octadiene (C8H12), or 1,3,5,7-cyclo-octatetraene (C8H8)] in frozen gas matrices at ca. 12 K results in two competing processes. One is partial dechelation of the polyene ligand to form [Fe(η2-polyene)(CO)3] species and the other is dissociation of a CO ligand to produce co-ordinatively unsaturated [Fe(η4-polyene)(CO)2] species. The photogenerated species were characterised by i.r. spectroscopy. Evidence is presented which indicates that [Fe(η2-polyene)(CO)3] species are responsible for s-cis⇄s-trans, ‘tub’⇄‘chair’, and π⇄σ rearrangements in [Fe(η4-C4H6)(CO)3], [Fe(η4-C8H8)(CO)3], and [Fe(η4-C4H4)(CO)3] respectively. The possibility of ring opening to form a metallocyclic intermediate is discussed in relation to the photoconversion of [Fe(η4-C4H4)(CO)3] into [Fe(η4-C4H4CO)(CO)3] in a carbon monoxide matrix. In a 13CO-doped methane matrix, facile 13CO/12CO exchange occurred for the Fe(CO)3 fragment of [Fe(η4-C4H4CO)(CO)3] but no exchange was found for the ketonic CO group. Ring-to-metal hydrogen migration forming [Fe(η5-C5H5)(CO)2H] and [Fe(η5-C7H9)(CO)2H] has been found to occur for [Fe(η4-C5H6)(CO)3] and [Fe(η4-C7H10)(CO)3] complexes via the co-ordinatively unsaturated fragments [Fe(η4-C5H6)(CO)2] and [Fe(η4-C7H10)(CO)2]. The intermediacy of η2-bound polyene species of the type [Fe(η2-polyene)(CO)4] has been established in the photodissociation of polyene ligands and the formation of [Fe(CO)5] in carbon monoxide matrices.

The cycloheptatrienyl carbonyl anions (C{sub 7}H{sub 7})M(CO){sub 3}{sup {minus}} (M = Ru, 1b; M = Os, 1c) have been isolated and structurally characterized as their Ph{sub 4}As{sup +} salts. Both 1b and 1c crystallize in the centrosymmetric space group P{bar 1} with two molecules per unit cell. For 1b: a = 12.308 (4) {angstrom}, b = 12.017 (5) {angstrom}, c = 11.326 (4) {angstrom}, {alpha} = 71.18 (2){degree}, {beta} = 80.93 (2){degree}, {gamma} = 90.15 (2){degree}. For 1c: a = 12.314 (2) {angstrom}, b = 12.025 (2) {angstrom}, c = 11.331 (2) {angstrom}, {alpha} = 71.12 (2){degree}, {beta} = 80.87 (2){degree}, {gamma} = 90.08{degree}. The structures were refined to R(F) = 0.0567 and 0.0268 and R{sub w}(F) = 0.0575 and 0.0278 for 3,686 and 3,905 reflections with F > 3.0{sigma}(F) for 1b and 1c, respectively. In both cases the seven-membered ring is coordinated to the metal in an {eta}{sup 3} fashion. The low-temperature-limiting {sup 1}H and {sup 13}C NMR spectra of 1c have been obtained and show that the same bonding mode is also adopted in solution. A comparison of the spectroscopic, structural, and chemical properties for the series of complexes (C{sub 7}H{sub 7})M(CO){sub 3}{sup {minus}} (M = Fe, Ru,more » Os) is made and explained in terms of increasing metal basicity upon descending the triad.« less

Ozdemir, Namik/0000-0003-3371-9874 WOS: 000245469800008 PubMed: 17413216 The title compound, [Zn(C15H11N7O4)(H2O)(2)](NO3)(PF6)center dot 3H(2)O, contains a mononuclear zinc(II) complex. The Zn2+ centre is seven-coordinated in a slightly distorted pentagonal-bipyramidal geometry, with the two water O atoms located in the apical positions, and the pyridine N atom, the two imine N atoms and two carbonyl O atoms of the uracil groups located in the equatorial plane. The charge is balanced by PF6- and NO3- anions.

ortho -Substituted aryllithium and aryl Grignard reagents react with (benzene)manganesetricarbonyl cation ( 1 ) to give good yields of the expected ring adducts. The presence of the ortho substituent(s) appears to be necessary for the satisfactory outcome of the reaction with aryllithiums. This reactivity opens up the possibility of preparing novel heterocyclic structures via the initial reaction of 1 with functionalised metallated arenes.

The synthesis and spectroscopic properties of the cycloheptatrienyl bridged ruthenium-iridium complex (μ-C 7 H 7 )Ru(CO) 3 Ir(CO) 2 ( 2 ) is described. 2 undergoes phosphine substitution reactions with PPh 3 at Ir and with DPPM at both metal centers. Within the series of complexes (μ-C 7 H 7 )M(CO) 3 M′(CO)PPh 3 (M = Fe, Ru; M′ = Rh, Ir) the rate of intermetallic carbonyl exchange increases upon descending a triad for M and M′.

WOS: 000316587800010, A series of stable acyclic aminals derived from L-(+)-aspartic acid were synthesized in excellent yields (up to 96%) and characterized by spectroscopic methods. They were applied as enantioselective catalysts in Henry reactions of nitromethane with various aldehydes in the presence of Cu(II) ions, affording the corresponding adducts in high yields (up to 90%) and enantioselectivities (up to 92% ee)., Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [210T147]; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK), We are grateful to The Scientific and Technological Research Council of Turkey (TUBITAK) for their financial support (210T147). G. K. thanks TUBITAK for a postdoctoral fellowship.