Volume 55, Issue 1

The synthesis of alkylated η 5 -cyclopentadienylvanadium(V) complexes t C 4 H 9 N=VCp R Cl 2 (Cp R = C 5 H 4 R, C 5 H 3 R 2 , C 5 HMe 4 , C 5 Me 5 ) is described. The compounds have been investigated by 51 V NMR spectroscopy; the 51 V resonances are found downfield of the unsubstituted complex t C 4 H 9 N=V(η 5 -C 5 H 5 )Cl 2 . The deshielding of the 51 V nucleus increases with the number of substituents R

The crystal structures of two compounds containing enaminone heterodiene systems and forming intermolecular hydrogen bonds N-H·O are reported: 1) 3-ethoxycarbonyl-2-methyl-4-pyridone (hereafter ETPY) and 2) 3-ethoxycarbonyl-2-phenyl-6-methoxycarbonyl-5,6-di-hydro-4-pyridone (hereafter EPPY). The crystal packing is controlled by intermolecular hydro­ gen bonds N-H·O = C connecting the heteroconjugated enaminone groups in infinite chains. In ETPY crystals the intermolecular hydrogen bond involves the heterodienic pathway with the highest π-delocalization that is effective for a very short N·O distance of 2.701(9) Å (average from two molecules in the asymmetric unit). Probably due to the steric hindrance, the hydrogen bond in EPPY is formed following the heterodienic pathway that involves the ester C = O group, although π-delocalization along this pathway is less than that along the pyridone-part pathway resulting in a longer N·O distance of 2.886(3) Å

In (alkyl)di(aryl)(8-dimethylamino-naphth-1-yl)phosphonium salts and in the parent phos­phines, there is no experimental evidence of dative N→P interactions. Conclusions to the contrary are based on the choice of improper standards of comparison

The thermolysis of gaseous Si 2 OCl 6 leads to a mixture of higher chlorosiloxanes with up to 8 silicon atoms per molecule. The unexpected formation of larger molecules from smaller ones by high temperature pyrolysis is due to three basic reactions: a) Formation of highly reactive O = SiCl 2 as an intermediate, b) insertion of O= SiCl 2 into Si-Cl bonds (growth reaction), and c) thermally induced elimination of SiCl 4 from chlorosiloxanes formed in (b). Temperature and time dependencies of the thermolysis have been investigated and are discussed

Chemical vapor transport is a suitable pathway to controllable syntheses of mixed spinel systems. Solid solutions of spinels on the basis of 3d transition metal oxides and gallium oxide can be prepared using various transport agents (TeCl 4 , Cl 2 , HCl). Transport processes observed are consistent with theoretical predictions

A single crystal of phenylmercury chloride (PhHgCl) was obtained by serendipity from a solution of diphenylmercury (HgPh 2 ) and dihydrolipoic acid in tetrahydrofuran / carbon tetrachloride. The crystal structure of PhHgCl is pseudotetragonal. It is best described in the orthorhombic space group Cmma with a = 6.856(1), b = 6.882(1), c = 14.309(2) Å (at 193 K), and Z = 4. The Cl-Hg-C moiety of the PhHgCl molecule is exactly linear. The bond lengths at the Hg atom are Hg-Cl 2.345(2) and Hg-C 2.044(9) Å. In the crystal, the molecules are arranged in double layers parallel to the a,b plane. In a model medium for the gastric juice (0.1 M DCl in D 2 O / [D 8 ]dioxan, 37 °C), HgPh 2 reacts to form PhHgCl. HgCl 2 , which would result from complete dearylation, cannot be isolated from the reaction mixture. However, it appears that a small equilibrium concentration of HgCl 2 may be present, because on addition of 1,4,7-trithiacyclononane (ttcn) and diethyl ether, the dichloride can be trapped as solid [Hg(ttcn) 2 ][HgCl 4 ]. We estimate that after oral uptake of HgPh 2 20 -90% are transformed into PhHgCl in the stomach after 30 min

Red crystals of Na 4 TiSe 4 were obtained by reacting an intimate mixture of Na 2 Se, Ti and Se at 750°C. Na 4 TiSe 4 is monoclinic, space group I2/a with a = 24.027(6), b = 7.346(4), c = 21.572(6) Å, (β = 104.52(2)°, Z = 16. Its crystal structure was determined from diffractometer data (AgK α-radiation) and refined to a conventional R of 0.036 for 2673 F 0′ s and 158 variables. The crystal structure is of a new type, characterized by the presence of discrete tetrahedral complex anions, [TiSe 4 ] 4- , which are arranged in slabs parallel to (100). The average Ti-Se bond length is 2.385(1) Å. The Na + cations are in different chalcogen environments with distorted octahedral, square pyramidal or planar configurations, respectively

By careful oxidation of the pure fluorochloroosmates(IV) with BrF 3 in dichloromethane the mixed pentavalent complex anions [OsF 5 Cl] - and cis -[OsF 4 Cl 2 ] - are formed. X-ray structure determinations on single crystals have been performed of (Ph 3 PNPPh 3 )[OsF 5 Cl]·CH 2 Cl 2 (1) (triclinic, space group P1̄, a = 12.153(5), b = 12.387(5), c = 14.229(5) Å , α = 70.07(1), β = 65.46(1), γ = 72.87(1)°, Z = 2) and cis-(Ph 3 PNPPh 3 )[OsF 4 Cl 2 ]·CH 2 Cl 2 (2) (triclinic, space group P1̄, a = 11.987(2) b = 13.083(2), c = 14.456(2) Å, α = 66.30(1), β = 65.47(1), γ = 71.22(1)°, Z = 2). Based on the molecular parameters of the X-ray determinations the IR and Raman spectra for the anions of 1 and 2 have been assigned by normal coordinate analysis. Due to the mutual trans influences the valence force constants of asymmetrically coordinated octahedral axes F • -Os-Cl′ differ from those of the symmetric F-Os-F axes. The data are for 1: f d (OsF • ) = 3.95, f d (OsF) = 4.07, f d (OsCl′) = 2.51 and for 2: f d (OsF • ) = 3.45, f d (OsF) = 3.97, f d (OsCl′) = 2.42 mdyn/Å

Zinc dichloride reacts with aminomethylpyridine (AMP) to the corresponding 1:1 adduct 1, whereas ZnBr 2 forms an ionic 1:2 complex of the type [(AMP) 2 ZnBr] + Br - 2, which loses one neutral coligand upon heating in Me-C (O)OEt to yield nearly insoluble (AM P)ZnBr 2 3. The condensation reaction of these compounds with acetone yields propylideneaminomethylpyridine zinc dichloride (4) and dibromide (5), respectively. The reaction of ZnI 2 with AMP and acetone gives propylideneaminomethylpyridine zinc dichloride (6) in quantitative yield. The structures of 3, 4, and 6 confirm the linear relationship between the Zn-N distance and the X-Zn-X angle in compounds of the type (L 2 )ZnX 2 with L 2 being a bidentate amino base, whereas short Zn-N bonds enforce small X-Zn-X angles. Compound 2 consists of separated ions in the solid state with a five coordinate zinc atom in a distorted trigonal bipyramidal coordination sphere

The zwitterionic λ 5 Si-tetrafluorosilicates F 4 SiCH 2 NMe 2 H (1) and F 4 SiCH 2 NMe 3 (2) behave as Lewis acids and react with [Me 3 NH]F (molar ratio 1:1) in aqueous solution to yield the ionic λ 6 Si-pentafluorosilicates [Me 3 NH][F 5 SiCH 2 NMe 2 H] (3) and [Me 3 NH][F 5 SiCH 2 NMe 3 ] (4), respectively. These hexacoordinate silicon compounds contain singly charged λ 6 Si-silicate anions ([F 5 SiCH 2 NMe 2 H] - , [F 5 SiCH 2 NMe 3 ] - ) with an SiF 5 C skeleton. Compounds 3 and 4 were isolated as the crystalline hydrates 3·H 2 O (yield 80%) and 4·H 2 O (yield 82%) which were structurally characterized by single-crystal X-ray diffraction. The Si-coordination polyhedra in the crystals of 3·H 2 O and 4·H 2 O are slightly distorted octahedra

The thermodynamical data of ammonium neodymium iodides (NH 4 ) 3 NdI 6 and (NH 4 ) 2 NdI 5 were derived by the determination of their decomposition equilibria by total pressure measurements. Moreover, solution calorimetry was applied. The enthalpies of formation of these phases were calculated from their heats of solution and from the enthalpies of formation and the heats of solution of N dl 3 and NH 4 I in 4n HI (aq.) at 298 K. Data by total pressure measurement: ⊿H° B (NH 4 ) 3 NdI 6,f,298 ) = -306,7 ± 4,9 kcal/mol; S°((NH 4 ) 3 NdI 6,f,298 ) = 152,8 ± 5,7 cal/K·mol; ⊿H° B (NH 4 ) 2 NdI 5,f,298 ) = -260,9 ± 4,2 kcal/mol; S°((NH 4 ) 2 NdI 3,f,298 ) = 114,3 ± 4,7 cal/K·mol. Data by solution calorimetry: ⊿H° B (NdI 3,f,298 ) = -154,3 ± 2,0 kcal/mol; ⊿H° B ((NH 4 ) 3 NdI 6,f,298 ) = -299,6 ± 3,2 kcal/mol; ⊿H° B ((NH 4 ) 2 NdI 5,f,298 ) = -255,2 ± 2,8 kcal/mol.

Dehydrogenation of 2-(1-piperidinyl)-benzaldehydes 1-3 using mercury(II)-EDTA gen­ erated the lactams 4-6, indicating a reversible reaction of a carbinolamine intermediate with the formyl group. The yields and oxidation rates decreased by 4-substitution in the piperidine moiety. The 2-(1-piperidinyl)-acetophenones 11, 16-19 showed a similar behavior with mercury(II)-EDTA but gave rise to a product pattern. The trans-benzoquinolizidones 12, 20, 23, 26, 29 resulted from the cyclic iminium compounds reacting with the acetyl group as nucleophile. By another oxidation these species were partially transformed to the quinolinones 13, 21, 24, 27, 30. An intermediate electrophilic neighboring of the carbonyl group with the cyclic hemiaminals led finally to the lactams 14, 22, 25, 28, 31. Mechanisms for the reactions are proposed

The catalytic oxidation of 2,4.6-tri-tert-butylphenol and 2,4,6-tri-tert-butylaniline with molecular oxygen and tert-butylhydroperoxide was investigated using biomimetic Mn-, Fe- and Co-complexes as catalysts. The catalytic activity and product distribution were determined and compared with those observed in the reactions of the well-known Co(salen) complex

The molecular structure of the title compound 2-hexanoyl-1-tribromomethyl-1,2,3,4-tetra-hydro-β-carboline (3), a potent inhibitor of complex I of the mammalian mitochondrial respiratory chain, has been studied by single-crystal X-ray diffraction analysis. In the crystal, two heterochiral molecules of 3 (i.e., one R- and one S-configured molecule each) were found to be connected with one other in pairs via two intermolecular hydrogen bonds [O(215) ··· H(212)′ and O(215)′ ··· H(212)] to form an overall achiral ‘dimeric’ subunit

Two new antifungal withanolides, (1) and (2) have been isolated from the defatted methanolic extract of Ajuga parviflora. Their structures were established as 3β,17β,20-trihydroxy-1-oxo-(20R, 22R)-witha-5,14,24-trienolide (1), 28-hydroxy-14,20-epoxy-1-oxo-(22R)-witha-2,5,24-trienolide (2) on the basis of spectroscopic data including two dimensional NMR tech­niques. The pyrrolizidine alkaloids senecionine (3) and integerrimine (4) are also reported for the first time from A. parviflora

Pyridines, thiazolopyridines and pyrazolopyrans containing glycinate residue were prepared by reacting N-cyanoacryloglycinate ylidenes with active methylene compounds via a Michael addition - intracyclization synthetic pathway. Simple routes for the synthesis of heterocycles with an amino acid residue were previously reported [1-3] as the incorportation of these residues improves the pharmacokinetics and toxicity of active compounds [4,5]. However, trials to deesterify these residues for coupling purposes were unsuccessful. So, we tried herein new approaches for synthesizing heterocyles carrying one or two glycine moieties with free carboxylic acid group to facilitate further peptide linkage [6] on one hand and on the other one could be able to form metal chelates, a property having a significant output on the toxicological behaviour [7]

Stable di-tert-alkylnitroxyl radicals, tert-butyl-tert-pentylnitroxyl (4a), di-tert-pentylnitroxyl (4b) and tert-octyl-tert-pentylnitroxyl (4c), the homologs of di-tert-butylnitroxyl (1), were synthesized from tert-alkyl amines 7a-c via the 3-tert-alkylamino-3-methyl-1-butynes 8a-c. Oxidation of 8a,b with hydrogen peroxide lead to relatively unstable N-tert -alkyl-N -(1,1-dimethylprop-2-ynyl)nitroxyl radicals 15a,b. The thermal stability, vapor pressure data, ultraviolet, visible and electron paramagnetic resonance spectra of 4a-c were recorded. The radicals were explored as potential inhibitors of unwanted alkene polymerization reactions at elevated temperatures, in comparison with the aliphatic di-tert-butyl nitroxyl (1), the alicyclic nitroxyl radicals 2,2,6,6-tetramethylpiperidin-1-oxyl (2) and 4-hydroxy-2,2,6,6-tetramethyl-piperidin- 1-oxyl (3), some commercial polymerization inhibitors, such as diethyl-hydroxylamine (Pennstop, 16), ammonium salt of N-hydroxy-N-nitrosobenzenamine (Cupferron, 17 ), bis(2,2,6,6- tetramethyl-4-piperidyl) sebacate (Tinuvin 770, 18), and the well-known spin traps 2-methyl- 2-nitrosopropane (19) and tert-butylhydroxylamine (20)

The applicability and synthetic potency of novel reagent, 2-aryl-1,1-dicyano-3-(phenylsulfo-nyl)propenes 3 to develop an expeditious convenient synthetic route of unique polyfunctionally substituted carbocyclic and heterocyclic sulfone systems is reported. Chemical and spec­troscopic evidence for the structures of the newly synthesized compounds are described. Some of the obtained compounds were tested for their antimicrobial activity