D. Ülkü

Synthesis of a water-soluble carbene complex and its use as catalyst for the synthesis of 2,3-dimethylfuran

Abstract 1,1′,3,3′-Tetrakis(p-dimethylaminobenzyl)-2,2′-biimidazolidinylidene, L2R (R=CH2C6H4NMe2-p) which contains four peripheral NMe2 substituents, was obtained from 4-dimethylaminobenzaldehyde by a three-step reaction sequence, and was used for the preparation of imidazolidin-2-ylidene Ru(II) and Rh(I) complexes 1 and 2. Etherial HCl readily protonates the NMe2 functionality on the carbene ligand of 1 to give the corresponding salt, 1′; whereas the reaction of 2 with HCl gave a hygroscopic and ill-defined rhodium species. In aqueous solution the salt 1′ is an efficient and active catalyst for intramolecular cyclisation of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran. The catalyst 1′ could be recovered by simple phase separation and the catalytic reaction was maintained for five different runs. All of the new compounds were characterised by elemental analyses, IR and NMR spectroscopy and the molecular structure of 1 was determined by X-ray crystallography.

cis-1,1'-Dimethyl-3,3'-diphenyl-2,2'-biimidazolidinylidene

The structure of the air-sensitive title compound consists of C20H24N4 molecules connected with a hydrogen bond. Neither the molecule as a whole nor the individual five-membered rings have a planar geometry. The dihedral angle between the best planes of the two phenyl rings is 50.87 (14)°. Weak intermolecular hydrogen bonding is observed between a C atom and an imidazoline N atom.

High temperature bromination VI: Bromination of benzobarrelene

Abstract The electrophilic addition of bromine to benzobarrelene in chloroform at 10° C followed by repeated chromatography combined with fractional crystallization allowed us to isolate ten products 12–21 Structural determination of these compounds revealed that the barrelene skeleton was rearranged completely. 18–21 are alcohol compounds which arise from hydrolysis of 12, 13, 14, and 15, respectively. High temperature bromination of benzobarrelene in decalin at 150 °C followed by repeated chromatography combined with fractional crystallization gave us 18 products. Nonrearranged products 24, 25, and 26 have been isolated in 50% yield. All compounds have been characterized properly, especially by 200 MHz 1H NMR and 50 MHz 13C NMR spectra. Furthermore, it has been concluded that high temperature bromination of bicyclic systems gives more non-rearranged products. If the molecule is more strained, the tendency to rearrange decreases as in the case of benzonorbornadiene.

Synthesis, spectroscopy, thermal behaviour and molecular structure of orotatotriethanolaminecopper(II) monohydrate

Abstract The orotatotriethanolaminecopper(II) monohydrate, [Cu(C5H2N2O4)(C6H15NO3)] · H2O, has been synthesized and characterized with physico-chemical methods (IR and UV-Vis spectroscopy, magnetic susceptibility, conductivity and thermoanalytical measurements) and X-ray diffraction. The structure derived from physico-chemical methods is consistent with that of the X-ray diffraction. The compound crystallizes in the monoclinic system, space group P21/n, with a = 8.6282(12), b = 16.9919(18), c = 10.6985(15) Å, β = 110.08(3)°, V = 1473.1(3) Å3, Z = 4. The copper atom is chelated by the deprotonated nitrogen pyrimidine atom and by the carboxylate oxygen atom of the orotate dianion ligand, and by the nitrogen and oxygen atoms of the triethanolamine ligand. The title compound has a distorted octahedral coordination geometry.

The first examples of di- and cis triaryl-3a,4,5,6-tetrahydroimidazo[1,5-b]isoxazoles and their ring-opening reactions

Abstract The Δ 3 -imidazoline 3-oxides 1 undergo diastereoselective cycloaddition with dimethyl acetylenedicarboxylate 2 to give 3a,4,5,6-tetrahydroimidazo[1,5- b ]isoxazoles 3 . Thermal and base induced ring-opening reactions of compounds 3 were demonstrated.

Synthesis and crystal structure of two dimeric cadmium(II) complexes bonded with pseudohalides, 1.1 and 1.3 bonding

Abstract Two different complexes were obtained from (dmpp) and Cd(II) ions with the aid of pseudohalide ions in non-aqueous solvents. The dinuclear complex formed with thiocyanate ions show, using XRD, to posses two 1.3 bond μ bridges [CdL(SCN)2]2. The other dinuclear complex was also seen to form with cyanate ions but with the μ-bridge in a 1.1 position [CdL(OCN)2]. All Cd atoms are located in a distorted octahedral environment in 1 and 2 complexes. The Cd…Cda distances are 6.032(4) Å in 1 and 3.704(3) Å in 2, respectively. The N—C—S and O—C—N angles are approximately linear as 178.1(3) and 178.6(3)° in 1 and 177.2(5) and 176.9(7)° in 2, respectively. The Cd—(μN,S-NCS)2—Cda bonds form a zig-zag structure in 1 and the Cd—(μO,N-OCN)2—Cda bonds form a distorted square planar in 2.

Novel enantioselective synthesis of trans-α-(2-carboxycycloprop-1-yl)glycines: conformationally constrained l-glutamate analogues

Abstract d - and l -α-(2-carboxycycloprop-1-yl)glycines were synthesized from trans -1,3-di(2-furyl)propenone. Conversion of the double bond to a cyclopropane is followed by the formation of an oxime ether. Enantioselective reduction of the oxime ether, separation of diastereomers and oxidation of the furane rings gave enantiomerically pure d - and l -CCG I and CCG II. The structure of oxime 7b was determined by X-ray crystal structure analysis. The key step is the oxazaborolidine catalyzed enantioselective conversion of oxime ethers to amines.

Synthesis, crystal structure and electrochemical behaviour of [2,6-bis(3,5-dimethylpyrazolyl)pyridine](dithiocyanato)cobalt(II)

Abstract A mononuclear cobalt(II) complex, [Co(dmpp)(SCN)2], was synthesized using 2,6-bis (3,5-dimethylpyrazolyl)pyridine (dmpp) and thiocyanate anion (SCN), and characterized by IR spectroscopy and single-crystal X-ray diffraction. In addition, cyclic voltammetric studies have been performed. The complex crystalizes in monoclinic space group C 2/c, with unit cell dimensions a = 15.2469(15), b = 9.1120(9), c = 14.0302(11) Å, β = 95.823(3)°. The cell containes 4 molecules.

4-Chloro-2-(4-oxopent-2-en-2-ylamino)-phenol

In the title compound, C 11 H 12 ClNO 2 , there is an intramolecular hydrogen bond between the amino group and the carbonyl O atom [N...O 2.686 (3) A]. Additional intermolecular hydrogen bonds between the phenol O atom and the carbonyl groups of neighbouring molecules [O...O 2.634 (2) A] form a polymeric chain. The molecule is not planar. The dihedral angle between the aromatic ring and the bidentate Schiff base moiety is 44.51 (7)°. The characteristic Schiff base N-C bond length is 1.339 (3) A.

BROMINATION OF NAPHTHALENE AND DERIVATIVES : HIGH TEMPERATURE BROMINATION XI

Abstract Thermal and photobromination of naphthalene and derivatives have been studied. Several hexabromo- (12, 13, 16 and 17), and tetrabromotetralin derivatives (23, 24, and 25) have been obtained as the major products, besides bromonaphthalene derivatives. Base-promoted elimination reactions of 12, 13, 16 and 17 provided di- (8) tri- (10) and tetrabromo-naphthalenes (22). A convenient method was developed for the synthesis of 1,3-dibromonaphthalene (26) starting from (24). The structures of these products were determined by 1H-, 13C-NMR data and X-ray structural analysis.