Volume 37, Issue 6

The reaction of 1,4-dibromobutane with bis(diphenylphospliino)methane (1) yields two products, one of which is identified as butane-1,4-bis[diphenyl(diphenylphosphinomethyl)-phosphonium bromide] (3 a). Transylidation of this bis-phosphonium salt using two equiv-alents of (CH 3 ) 3 P = CH 2 affords the bis-ylide [CH 2 CH 2 P(C 6 H 5 ) 2 = CH-P(C 6 H 5 ) 2 ] 2 (4) in high yields. This conversion can be reversed on treatment of 4 with etheral HCl (to give 3b). Methylation of 4 with CH 3 I occurs at phosphorus, however, and produces the bis-semiylide salt (5), [CH 2 CH 2 P(C 6 H 5 ) 2 CHP(C 6 H 5 ) 2 CH 3 ] 2 2 ⊕ 2I⊖. Transylidation of 5 (again with (CH 3 ) 3 P = CH 2 ) leads to the bis-carbodiphosphorane (6), [CH 2 CH 2 P(C 6 H 5 )2 = C = P(C 6 H 5 ) 2 CH 3 ] 2 . All compounds were characterized by elemental and detailed NMR analyses. The second product of the above quaternisation reaction is a cyclic bis-phosphonium salt (2) with a seven-membered ring structure.

The red, diamagnetic complex [Mo(NO)(terpy)(CN)(HNO)] • 2H 2 O crystallizes in the triclinic space group P1̅(C 1 i -No2) with cell constants a = 867.1(3), b = 1008.4(4), c = 1095.6(3) pm, a = 73.64(3)°, β = 83.54(3)°, γ = 83.16(3)°, and Z = 2. The final R value of the single crystal X-ray analysis is 0.063 for 1922 unique reflections. The structure consists of neutral complexes of [Mo(NO)(terpy)(CN)(HNO)]. The geometry about the molybdenum is a distorted pentagonal bipyramid with a linear NO and CN group in the axial positions, a triclentate terpyridine ligand and an O,N-coordinated HNO 2- ligand in equatorial positions.

The acceptor number AN and the polarity parameters Z and E T (30) were determined for a series of alcohols applied as media in the study of kinetic solvent effects. The alcohols thus characterized are methanol, ethanol, 1-propanol, 1-butanol, 2-butanol, 2-methyl-2-butanol, 3-pentanol, 2-chloroethanol, 2-methoxyethanol, 2-phenylethanol, 2-cyanoethanol, benzyl alcohol, 3-ethyl-3-pentanol, 2,4-dimethyl-3-pentanol, and 3-ethyl-2,4-dimetliyl-3-pentanol. In addition, AN was determined for 1,2-dichloroethane and Z for the binary solvent mixtures methanol/2-methyl-2-butanol, ethanol/2,2,2-trifluoroethanol. and methanol/pyridine. The data obtained are correlated and the parameters AN, Z, and E T (30) are critically compared.

The new compound Rb 2 SnO 2 was obtained as a light yellow powder by heating mixtures of the binary oxides (RbO 0.48 + SnO, Rb: Sn = 2:1) under argon (sealed Ag cylinders, 600 °C, 3d). Subsequent annealing (550 °C, 8d and 500 °C, 17 d) led to light yellow transparent single crystals. Rb 2 SnO 2 is extremely sensitive to moisture and decomposes into black products. It crystallizes orthorhombicly in the space group P2 1 2 1 2 1 -D 4 2 , with a = 5.76 1 , b = 7.49 3 , c= 11.16 7 Å, Z = 4, d rö = 4.43 and d pyk = 4.46 gcm -3 , R= 11.8 and Rw = 12.0%. Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, and the Madelung Part of Lattice Energy, MAPLE, have been calculated. Isotypic K 2 SnO 2 was obtained similarly as a brown powder, a = 5.57 9 , b = 7.24 6 , c = 16.74 4 Å.

The crystal structure of 2 SbBr 3 · biphenyl consists of pyramidally shaped SbBr 3 molecules and planar biphenyl molecules which form a centrosymmetric complex through bonding of the Sb atoms to the phenyl rings. The distance of the Sb atoms to the phenyl ring planes is 323 pm. Taking into account intramolecular bonds Sb-Br at an average of 250.9 pm, an intermolecular Sb···Br contact at 369.5 pm and the π-donor-acceptor inter-action the Sb coordination is distorted ψ-octahedral. The structure is discussed with regard to related compounds.

PPh 4 [VOBr 4 ] was prepared by the reaction of PPh 4 Br with VOBr 3 in CH 2 Br 2 solu-tion. The structure of the dark violet crystals was determined with X-ray diffraction. PPh 4 [VOBr 4 ] crystallizes in the space group P4/n with the lattice constants a = 1275.9 and c = 784.5 pm with two formula units per unit cell. The structure type corresponds to the frequently encountered AsPh 4 [RuNCl 4 ] type. The VOBr 4 - ion forms a square pyramid; the V = O bond has a length of 155 pm. In the IR spectrum, the V -O stretching vibration appears at 922 cm -1 .

[Ni(C 2 H 5 N 4 O 2 ) 2 ] · HCl · H 2 O, C 4 H 10 N 8 NiO 4 · HCl · H 2 O, forms triclinic crystals, Mr = 347.36, P1̄, a = 7.219(2), b = 7.316(1), c = 11.797(3) Å, α = 73.89(2), β = 86.37(2), γ = 85.71(2)°, V = 596 Å 3 , Z = 2, d c = 1.93 Mgm -3 ; final R w = 0.028 for 1957 reflections. The planar complex molecules form equidistant stacks along b, with the molecular planes inclined at ~29° to the stacking axis. Molecules of adjacent stacks are linked along a by an intermolecular H bridge coexistins with the usual intramolecular H bridges. The analogous Pt complex, C 4 H 10 N 8 O 4 Pt · HCl · H 2 O, Mr = 483.74, a = 6.480(4), b = 16.115(5), c = 12.194(9) Å, β = 101.27(4)°, V = 1249 Å 3 , Z = 4, dc = 2.57 Mgm -3 , P2 1 /a, crystallizes in a columnar structure with a Pt-Pt separation of ~a/2 ≈ 3.24 Å. Due to twinning, faking orthorhombic symmetry, a complete structure determination was not possible.

Reductive dehalogenation of BiCl 3 with Na 2 W 2 (CO) 10 leads to Bi 2 [W(CO) 5 ] 3 (1), which contains an axial Bi 2 ligand side-on coordinated to three W(CO) 5 groups. The star-type arrangement of three metal carbonyl moieties around a Bi 2 axis with a very short Bi-Bi bond distance (281.8(3) pm) and a Bi 2 W 3 core of approximate D 3h symmetry is proved by an X-ray analysis (R 1 = 0.041). 1 is thus the highest homologue of a series of complexes X 2 [W(CO) 5 ] 3 (X = As, Sb, Bi) and is the first stable molecular compound to contain a Bi 2 ligand.

The He(I) and He(II) photoelectron spectra of M[Co(CO) 4 ] 2 and M[Mn(CO) 5 ] 2 complexes (M = Zn, Cd, Hg) are reported. Bands attributable to metal-metal bonds, metal d-levels and CO orbitals are assigned in agreement with a semi-ionic model, i.e. M 2+ and [M'(CO) n ] - . Relativistic effects prove to be important in assigning these ultraviolet photoelectron spectra.

cis-Chloro(2-N,N-dimethylaminophenyl)bis(triphenylphosphane)platinum(II) and cis-Bromo(2-N,N-dimethylaminophenyl)bis(triphenylphosphane)platinum(II) have been syn-thesized and converted to the corresponding trans-isomers. The crystal and molecular structure of imns-chloro(2-N,N-dimethylaminophenyl)bis(triphenylphosphane)platinum-(II) has been determined by X-ray diffraction. The molecular structure is discussed with respect to possible coordination of the ortho-located N,N-dimethylamino substituent with the central atom.

Water loss from protonated gaseous 1-decalon and 8α-methyl-1-decalon under the condition of chemical ionisation mass spectrometry proceeds via at least three distinct pathways, all of which commences with a [1.2]-hydrogen or [1.2]-methyl migration, thus giving rise to the formation of the central intermediate 10. H 2 O loss from 10 proceeds either directly, involving a hydrogen from the position (C-4a) (Scheme 3; pathway 10 →15 →16), or from the rearranged ions 17 and/or 20. The fact that eis-and trans-8α-methyl-1-decalones and their deuterated isotopomers behave essentially identical is explained by loss of the stereochemical integrity of the ring conjunction. The mechanistic features of this unusual process (Scheme 2) have been explored by semi-empirical MINDO/3 calculations for the model system 23 (Scheme 4). The calculations reveal that there are two competing pathways for CH 3 migration, one involving a sequence of [1.2]-shifts (23 →24 →25 →26→27), the other -being energetically less favoured -corresponds to a direct [1.3]-methyl migration (Scheme 6; 23 →33 →27), in which the methyl group migrates with retention of configuration. This process is symmetry forbidden. For the corresponding symmetry allowed [1.3]-methyl migration with inversion of configuration of the migrating group no pathway could be detected computationally. Both the experi-mental and theoretical investigations allow one to draw a detailed picture of H 2 O loss from protonated cyclic ketones in the gas phase. -The syntheses of the labelled substrates are described in detail.

Pyridinium Dithiocarboxylates, Picolinium Dithiocarboxylates Pyridinium and picolinium dithiocarboxylates, which can be readily obtained from the corresponding dithio acids and pyridine or picoline, were found to sublimate easily under the conditions of ca. 3 torr at room temperature.

α-(Thiocylthio)methylphenylketones, 2,4-Disubstituted 1,3-Thiazoles, Caesium Dithioates α-(Thioacylthio)methylphenylketones were found to be obtained in almost quantitative yields from caesium dithioates and a-phenacyl bromide. Refluxing of these ketones with ammonium acetate in gracial acetic acid affords the corresponding 2,4-disubstituted 1,3-thiazoles. While, the similar reaction of α-(thioisobutyrylthio)methylphenylketone gives the dithiafulvene (4).

The nitric oxide complex of hagfish hemoglobin exhibits electron spin resonance spectra centered around g = 2 with rhombic symmetry. The six coordinated spectrum is not influenced by protonation or presence of inositol hexaphosphate. Thus, the critical substitutions at E 7 (His → Gln) and E 11 (Yal → Ile) do not disrupt the proximal histidineiron bonds in the nitrosyl complex of this primitive hemoglobin, though the same type of substitution are known to cause destabilization of R quaternary structure in tetrameric mammalian nitrosylhemoglobins. This difference could be related to the difference in tension existing in the respective hemes of tetrameric and monomeric hemoglobins.

Preparation and purification of 3-acylates of ingenol (1a) structurally related to naturally occuring, irritant and cocarcinogenic principles are described. It is shown that 3-acylates partly rearrange to corresponding 5-acylates when they are chromatographecl. From the 3-acylates or from ingenol (1a) a mixed and a symmetric ingenol-3,20-diacylate is synthesized respectively. Ingenol-5,20-acetonide (2a) is rearranged to its ⊿ 7.8 -isomer 3b. Starting with 3b ⊿ 7.8 -isoingenol (3a) and the 3-tetradecanoate of ⊿ 7.8 -isoingenol (3d) are prepared. Most of the ingenol derivatives prepared are tested for their irritant activity on the mouse ear.

A reinvestigation of the reactivity of N-isopropylidene cyclohexylamine to methyl acrylate by GC-MS analysis has shown that the major product is the β-aminoester (9) formed by the N-alkylation of cyclohexylamine which may be generated by a dimerisation-elimination sequence. A number of other products resulting from N-and C-alkylation of the ketimine have been identified.

Keywords The synthesis of 11 -methoxynauclefine and 11 -methoxyrutaecarpine is described starting from harmaline.

PHI has recently been isolated from porcine duodenum as a new peptide factor with VIP-like activities. Its primary structure corresponds to a linear heptacosapeptide amide characterized by a remarkable sequence homology to the other known members of the glucagon family. The synthesis of this hormone candidate has been performed applying the strategy of overall acid-labile side-chain protection and the fragment condensation procedure. Upon assembly of the fragments to the fully protected heptacosapeptide amide, acidolytic deprotection with trifluoroacetic acid followed by purification of the resulting crude product via ion exchange chromatography and partition chromatography yielded synthetic PHI at a high degree of purity as judged from different analytical tests. Comparative analyses of the synthetic and natural product by means of chromatographic and biological assays confirmed the identity of the two PHI preparations.

N-Trifluoromethyl-S-trifluoromethylimidosulfurfluoride and chloride CF 3 NSX(CF 3 ) (X = F, Cl) were obtained from cyanogen fluoride and trifluoromethylsulfurtrifluoride and subsequent halogen exchange, respectively.

Diisobutylaluminum hydride i Bu 2 AlH reacts with N-heterocycles L (L = pyrazine, 2,2'-bipyridine, 4,4'-bipyridine) via single electron transfer to yield 1:1 radical complexes [L(Al i BU 2 )·].

The calcium isotope separation at a strongly acidic exchanger resin as a function of the concentration of a LiCl solution is investigated in column experiments. Whereas an enrichment of the heavier calcium isotopes in the solution phase is found with a 3 M LiCl solution, an inverse effect is obtained with 8 M and 12 M LiCl solutions. The separation effect e for the 12 M solution is found to be the highest calcium enrichment in a system without a complexing agent. The results are compared with those for other electrolyte solutions and can be explained by the anion/cation interactions.

The 13 C NMR parameters of the title compounds are assigned by heteronuclear triple resonance experiments 13 C{ 1 H, 11 B}. The magnitude of the coupling constants J( 13 C 11 B) corresponds roughly with J( 13 C 13 C). The chemical shifts δ 13 C reveal B-C(pp) π bonding which is, however, rather weak when compared with C + -C(pp) π bonding in phenylethynyl carbocations.

The ESR spectra of novel paramagnetic comple-xes between cis-dichlorodiammineplatinum(II) and cytosine or cytidine in aqueous solution are presented and discussed. The results imply a complex containing a binuclear metal-metal bonded platinum moiety with an unpaired electron spin delocalized over the dz 2 -orbitals.

A synthesis of vincamine (1) and eburnamo-nine (2) is reported which involves a new route to the key intermediate (8).