Volume 34, Issue 11

The covalent carbamoyl compounds η 5 -C 5 H 5 Ru(CO)(L)(CONH 2 ) (L = CO, MeCN, MeNC, PPh 3 , PEt 3 ) and η 5 -C 5 H 5 Os(CO) 2 (CONH 2 ) are formed by the reactions of the cationic complexes [η 5 -C 5 H 5 Ru(CO) 2 (L)] + (L = CO, MeCN, MeNC, PPh 3 , PEt 3 ) and [η 5 -C 5 H 5 Os(CO) 3 ] + with liquid NH 3 below 10 °C. In contrast, the reaction of [η 5 -C 5 H 5 Ru(CO) 2 (η 2 -C 2 H 4 )]PF 6 with liquid NH 3 yields the quarternary ammonium salt [η 5 -C 5 H 5 Ru(CO) 2 (CH 2 CH 2 ⊕ NH 3 )]PF 6 . With the cationic complexes {[η 5 -C 5 H 5 M(CO) 2 ] 2 (P̑P)} ++ (M = Fe, Ru; P̑P = Ph 2 PCH 2 CH 2 PPh 2 ) it was possible to prepare the dinuclear P̑P bridged carbamoyl derivatives [η 5 -C 5 H 5 M(CO)(CONH 2 )] 2 (P̑P).

The crystal structure of the monoclinic η5-C 5 H 5 RU(CO) 2 (CONH 2 ) has been determined by X-ray diffraction (space group P1̄ with Z - 4 and a = 1248,3 pm, b = 963,3 pm, c = 845,2 pm, α= 97,35°, β= 106,11°, and γ= 99,32°). The Ru is pseudo-octahedrally coordinated to the η 5 -C 5 H 5 ring, the two CO groups and the CONH 2 ligand with a planar RuC(O)N-moiety. Dimers are formed by N-H···O hydrogen bonds connecting the carbamoyl ligands of two molecules. Further hydrogen bonds link these dimers to form a helical chain.

Addition of permethylated triaminoiminophosphorane to silylated aminodiiminophosphorane yields an acyclic di(phosphazane)betaine. The structure was determined by X-ray crystallography.

The structure of α-MnSO 3 ·3H 2 O, space group P2 1 /n, Z = 4, D m = 2.42, Dx = 2.425gcm -3 , a = 6.6501(3), b = 8.9065(4), c = 8.7925(4) Å, β=96.105(3)°, was solved by the Patterson method and refined by Fourier and least-squares methods. All H atoms were located. The final R’s are 2.1/3.2% for the 1749 observed/2280 measured reflexions. Coordination of Mn is octahedral involving O atoms from three water molecules and three different sulfite groups. MnO 6 octahedra are linked through sulfite sulfur. The Mn-O distances range from 2.149(2) to 2.314(2) Å. The S-O distances of the sulfite group are 1.529(2), 1.529(2) and 1.544(2) Å. The first two are elongated by one, the latter by two H bonds. The O-S-O angles are 103.25(9), 104.18(9) and 104.35(9)°.

The preparation and characterization of 4,4′-bi-1,2,4-triazole is described. The compound is a strong, polydentate, polynucleating nitrogen donor. Two complexes, M(btr) 2 (NCS) 2 H 2 O M=Co, Ni, are described. The vibrational spectra of ligand and complexes are compared. A structure for the complexes is proposed.

The photolytical reactions of η 5 -C 5 H 5 Mo(CO) 3 CH 3 (1) or η 5 -C 5 H 5 W(CO) 3 CH 3 (2) with N 3 CO 2 C 2 H 3 (3) in CH 2 Cl 2 yield the “nitrene” complexes [(η 5 -C 5 H 5 JMoO)(μ-NCO 2 C 2 H 5 ) 2 (4), [(η 5 -C 5 H 5 )WO] 2 (μ-NCO 2 C 2 H 5 ) 2 (5) and [(η-C 5 H 5 JMoO] 2 (μ-NCO 2 H 5 )(μ-O) (6) together with some η 5 -C 5 H 5 Mo(CO) 3 Cl (7) and η 5 -C 5 H 5 W(CO) 3 Cl (8), proving that the solvent takes part in the reaction. Compounds 4, 5 and 6 contain bridging imido groups, arising from the capture of probably free nitrenes NCO 2 C 2 H 5 by organometallic species. Evidence for the presence of free nitrenes in the reaction medium is provided by the isolation of urethane (9), tetrachlorethene (10), 7 and 8 as secondary products.

Tetrachlorothallates MTlCl 4 (M=K, Rb and NH 4 ) crystallizing in the tetragonal CaWO 4 type were obtained by crystallization from highly concentrated aqueous TlCl 3 solutions containing small amounts of MCI. The structural parameters of NH 4 TlCl 4 were determined from single-crystal data. The indates MInCL 4 (M=K, Rb and NH 4 ) are isotypic. The vibrational spectra of the tetrachlorothallates were discussed.

A simple procedure for derivation of octant rules for optically active molecules containing a chromophoric group is developed within the framework of Kuhn's classical model of coupled oscillators. The important feature in this derivation is the clue that the locus of the center of gravity of the atoms not belonging to the chromophoric group and the direction of maximum polarizability of this ensemble of atoms are not independent. The octant rule for carbonyl compounds arrived at by this procedure is in agreement with the empirical one. A newly derived rule for cis-azo compounds is verified by empirical data.

During thermal annealing of the frozen polycrystalline samples of aqueous carbohydrate (dextran, melibiose, maltose, glucose, and xylose) solutions y-irradiated at 77 K the formation of peroxy radicals by addition of oxygen to the primary carbon-based radicals was observed at 190-220 K by the ESR method.

The electric dipole moments of acetyldiazomethane (MeCOCHN 2 ) and 1-acetyl-1-diazo-ethane (MeCOMeN 2 ) between 10 and 70 °C have been measured. Using appropriate group and bond moments, the concentrations of the two rotamers present in each have been calculated and, hence, the equilibrium constant for the cis ⇆ trans equilibrium at the various temperatures. The change in standard enthalpy (⊿H°), standard free energy (⊿G°) and standard entropy (⊿S°) are reported for the conversion of one mole of cis isomer to trans isomer.

Liquid Crystals, Cyclohexyl-phenyl-pyrimidines, Dicyclohexyl-pyrimidines The synthesis and mesomorphic properties of three new classes of cyano-substituted cyclohexyl-phenyl-and dicyclohexyl-pyrimidines are reported. The compounds are colourless, chemically and photochemically stable and have wide nematic mesophases. The thermal compatibility of the new compounds with other nematic liquid crystals is excellent. The large static positive dielectric anisotropics are shown to depend strongly on the position and number of hydrogenated rings as well as on the alkyl chain lengths within a homologous series. The reported bulk viscosities vary considerably among homologues. Hydrogenating the ring adjacent to the cyano end group causes η to increase, whereas a considerable viscosity reduction compared to nonhydrogenated homologues was found by hydrogenating the ring adjacent to the alkyl end group. The measured refractive indices of the new compounds are comparable to those of biphenyls.

Diethoxybilirubin diethyl ester crystallises triclinic P1 with a = 13.903(5), b = 17.211(7), c = 9.831(5) Å, α= 110.07(3), β = 111.22(3), γ = 69.04(3)°, Z = 2, D x - 1.15 gcm -3 . The two pyrromethene systems of the tetrapyrrole are orientated almost perpendicular to one another (interplanar angle = 91.5°). Considerable bond delocalisation is observed within the individual pyrromethene units, which contain intramolecular N-H···N hydrogen bonds of length 2.73 and 2.80 Å. Parallel stacking of the chromophores is not observed in the crystal lattice.

endo-2-Dimethylphosphono-exo-2-hydroxy-(-)-camphane (2) is prepared and the structure confirmed by X-ray data. The complete assignment of the 13 C NMR spectrum of this conformationally rigid derivative leads to a Karplus-type function for the vicinal 3 J(CCCP) coupling constant in α-hydroxy phosphonates.

The 1,3-diphenylisobenzofuran oxidation reaction was investigated in methanolic and dodecylammonium propionate reversed micellar solutions using fluorescein sodium as photosensitizer. It was found that aniline remarkably enhanced the furan oxidation in methanolic solutions but inhibited it in reversed micellar solutions. This enhancement effect occurred more effectively at lower oxygen concentrations. It was proposed that, in the former solutions, the radical mechanism (Type I) might be involved in the furan oxidation in the presence of aniline besides singiet oxygen mechanism (Type II). The reversed micelle seems to inhibit the Type I reaction, resulting in no enhancement of the furan oxidation by aniline.

The solvent, temperature, concentration, pH, substitution as well as anion dependency were measured of the reaction rate constants for thermal cis→trans isomerization of quarternary stilbazolium salts (1). From the ionic conductance of 1 in the different solvents used the dissociation constants as well as the degree of dissociation were calculated according to the method by Shedlovsky. The rate of the cis→trans isomerization is extremely sensitive to the solvent. In protic solvents the reaction rate decreases linearly with increasing Z-values indicated by Kosower. In dipolar aprotic and non-polar solvents the reaction rate is independent of the solvent parameters. It is concluded that the thermal cis→trans isomerization of stilbazolium salts (1) in dilute solutions occurs within the cation independently of the anion. The enormous increase of the rate of isomerization from stilbenes and stilbazoles to stilbazolium salts as well as their strong dependency on the solvent is due to the positive charge in 1 and the associated specific solvation phenomena. A possible polar transition state is discussed.

The reaction of 5,5-diphenyl-γ-butyrolactone (3) with primary amines and ethyl γ-γ-diphenyl vinyl acetate with Aqu HBr in acetic acid served as examples for the exception to Baldwin rules for 5-exo-tet and 5-exo-trig ring closures. The structure of the reaction product of 3 with primary amines have been assigned on the basis of spectral data and conversion to γ-γ-diphenyl vinyl substituted acetamides, the authentic samples of which were prepared by an unambigous route of synthesis.

Three known furanoid diterpenes Teucrin P 1 (2), Teucrin H 3 (3) and Montanin B (4) have been isolated for the first time from the bitter fraction of the aerial parts of Teucrium polium L. In addition two new diterpenes of this type Teupolin I (5) and Teupolin II (6) have been also found in the plant extract. The structure and stereochemistry were established using spectral methods and chemical evidence.

UV irradiation of S-(3′-thienyl)2-chloro-thionicotinate (1) in benzene solution leads via dehydrohalogenation and cy clization in competition to α-cleavage to formation of thio-lactone 2 besides aldehyde 3 and disulphide 4. 2 contains a new heterocyclic ring system which has been confirmed by spectroscopic methods.

HPLC-Studies of the piperolide-containing fraction from piper sanctum revealed the presence of a new piperolide-like substance, which has been isolated by column-adsorption chromatography on silica-gel in a yield of 0.1 per cent. The substance has been identified as (5E)-piperolide by spectroscopic techniques and by transforming it into the tetrahydroderivative, threo-4, which had been correlated with threo-3, a derivative of known configuration [1]. The (E)-isomer may be an artefact produced from the (Z)-isomer by the action of light. Both isomers when dissolved in benzene or chloroform and exposed to light, yield an equilibrium mixture of 5Z : 5E isomers in the ratio 62:38. Dehydrogenation of either threo- or erythro-3 with DDQ gives nearly the equilibrium mixture of (5E)- and (5Z) -piperolides.

Condensation of aminomethy lene-malononitrile (1a) with aromatic aldehydes and dimethylformamide-dimethylacetal, resp., leads to benzylidene-malononitriles (2a, b) and to dimethylaminomethylene-malononitrile (2e), resp. A mechanism of this cleavage of a C=C double bond is discussed. Several substituted enaminonitriles (1e-i) are prepared and the reactivity against aldehydes is studied. Thus, condensation of 3-Amino-2-cyano-crotononitrile (1e) with aldehydes leads to 2-amino-4-phenyl-1,3-butadiene-1,1-dicarbo-nitriles (3). 4-Oxo-2-phenyl-1,2,3,4-tetrahydro-5-pyrimidine-carbonitriles (4) are yielded by the reaction of 3-amino-2-cyano-crotonic-carboxamide (1h) and 3-amino-2-cyano-cinnamamide (1i), resp., with aldehydes. Condensation of 1h and 1i with ethyl ortho-formate leads to 3,4-dihydro-4-oxo-pyrimidine-carbonitriles (6).

Quinolinium Salts, Redox Reactions Quaternary salts of 3-quinolinecarboxamide and 3-quinolinecarbonitrile react after addition of ZnCl 2 with ethanol (or 2-propanol) to the corresponding 1,4-dihydroquinoline and ethanol (or propanone). This hydride transfer can be achieved with aluminium-triisopropoxide, too. Lipophilic insertionproducts (4,5,7,8) react with ethanol (or 2-propanal) after ZnCl 2 addition to quinolinium-alcoxides, and then to the 1,4-dihydro-quinoline and ethanal (or propanone).

Quaternary isoquinolinium salts react with an equivalent amount of anionic bases to a cyclocondensate (3), which has lipophilic properties. Other carboxamides insert after deprotonation by potassium tert-butoxide the isoquinolinium ring, too. The resulting product 5 is stable. Aluminium-triisopropoxide can reduce substituted isoquinolinium salts. 3 and 5 react with 2-propanol and ZnCl 2 to give first a solution of isoquinolinium iso-propoxide and then in a redoxreaction the corresponding 1,2-dihydroisoquinoline. That are modelreactions for the enzymatically catalyzed alcoholoxidation by the coenzyme NAD + .

Methilation of the aetiobiliverdin-IV-γ-lactimether yields a lactam-N-methylated derivative the structure of which was proven by an ether cleavage and 1 H NMR spectroscopy. The configuration (Z,Z,Z) was deduced from 1 HNMR experiments. Photo-isomerization exclusively forms the (E,Z,Z) diastereomer. By conformational analysis using the LIS technique and correlations of UV-VIS spectra and PPP-type calculations a more or less helical arrangement for the two diastereomers was confirmed. The twisting is maximal at the methine single bond adjacent to the site of N-methylation, the overall geometry seems to be much more distorted than the non methylated derivatives.

A low temperature X-ray study of the enol of benzoylacetone indicates fixed positions of the C and O atoms within the enolic ring system and an extensive bond delocalisation over these atoms. The distribution of electron density between the two oxygen atoms shows that the enolic hydrogen is spread over a wide range. This is in accordance with a structural model proposed by de la Vega, whereupon the C and O atoms are kept fixed in their average positions during a tunneling process of the hydrogen between the two oxygen atoms. With this conception, the chemical shifts in the 17 O and 13 C NMR spectra, the 13 C 13 C spin coupling constants and the temperature independance of these values can be explained.

The migratory aptitude of halogens and simple nucleophilic substituents X in the molecular ions of alkynes 1-11 and alkenes 12-17 was investigated by electron-impact mass spectrometry using low and high resolution, metastable analysis and 2 H-labelling.

The infrared P 2 O 7 and COP vibrations of thiamine diphosphate tetrahydrate have been assigned by comparison with related species.