An efficient synthesis of 6-formyl-1,2-dihydro-2-oxo-3-pyridinecarboxylic acid and some carbonyl derivatives of it and its 6-acetyl homologue

Starting with 1,1-dimethoxy-2-propanone ( 1 ), 6-formyl-1,2-dihydro-2-oxo-3-pyridinecarboxylic acid ( 5a ) has been prepared in large quantities by a highly efficient, 4-step synthesis. This compound, along with its one carbon homologue, 6-acetyl-1,2-dihydro-2-oxo-3-pyridinecarboxylic acid ( 5b ) has been reacted with several carbonyl derivative forming reagents to provide a series of side chains for β-lactams. Among these carbonyl derivatives are styrylamides which were prepared from Wittig and Horner-Emmons reagents. The preparation of the phosphonium salts and phosphonate esters is also described.     

Zinc(II) as a versatile template for the design of dipolar and octupolar NLO-phores

Thermally stable dipolar and octupolar (D2d, D3) NLO-phores are readily accessible by combining one, two, or three 4,4'-bis(dialkylaminostyryl)-[2,2']-bipyridyl ligands with zinc(II) salts. The off-resonant beta0 values point out the superiority of octupoles versus dipoles in terms of nonlinearity/transparency tradeoff. The octahedral tris(bipyridyl)zinc(II) complex exhibits a very large beta0 value (241 x 10-30 esu), which is the largest ever reported for octupolar molecules.     

Organically modified sols as pseudostationary phases for microchip electrophoresis

We demonstrate that the selectivity of microchip electrophoresis separations is greatly improved by the presence of organically modified silica (Ormosil) sols in the run buffer. A negatively-charged N-(trimethoxysilylpropyl)ethylenediamine triacetic-acid (TETT)-based sol is used for improving the selectivity between nitroaromatic explosives and a methyltrimethoxysilane (MTMOS)-based sol is employed for enhancing the microchip separation of environmental pollutants, aminophenols. These sols are added to the run buffer and act as pseudostationary phases. Their presence in the run buffer changes the apparent mobility of studied solutes, and leads to a higher resolution. The observed mobilities changes reflect the interactions between the Ormosil sols and the solutes. Relevant experimental variables have been characterized and optimized. The diverse chemistry of Ormosil sols should be extremely useful for tailoring the selectivity of a wide range of electrophoresis microchip separations.     

Selective partial reduction of various heteroaromatic compounds with bridgehead nitrogen via Birch reduction protocol

[reaction: see text] For the first time various heteroaromatic compounds with bridgehead nitrogen, including indolizines, bispyrrolopyrimidines, pyrroloquinolines, pyrroloisoquinolines, and bispyrrolopyrazines, were selectively partially reduced under Birch reduction conditions. It was found that the double bond in the fused heterocycles which possesses the highest LUMO density can be selectively reduced under these conditions. Indolizine 6, containing an ester group at C-6, was reductively alkylated to give dihydroindolizines 8 and 9 possessing a quaternary carbon center in good yield. It was found that ambident substrate 12, under Birch reduction conditions, underwent smooth partial reduction to give 4,5-dihydroquinoline 14 as a sole product with no evidence of reduction of the side chain olefin. It was also shown that electron-rich pyrroloisoquinoline 15, which cannot be reduced via catalytic hydrogenation conditions, was efficiently transformed into its dihydrocounterpart 16 by using the Birch reduction protocol. Finally, it was shown that various fused diazines were smoothly and stereoselectively reduced under Birch reduction conditions to give trans-4,5-disubstituted dihydropyrimidines 30 and 32 in virtually quantitative yields.     

Fluordiazadiphosphetidine, 3. Mitt.: Die thermische Behandlung von 2,2,2,4,4,4-Hexafluoro-1,3-dimethyl-1,3,2,4-diazadiphosphetidin unter Druck in Gegenwart von Phosphor(V)fluorid und Alkalimetallfluoriden

Prolonged heating of (CH₃NPF₃)₂ in a sealed tube at 120°C yields (CH₃N)₄P₃F₇ and PF₅. Under the experimental conditions these compounds react to (CH₃N)₄P₃F₆ ⁺PF₆ ^–. Reaction of (CH₃NPF₃)₂ in the presence of PF₅ leads to a marked decrease in the formation of the ionic compound. The influence of the fluoride donating saltsMF (M=Li, Na, K, Cs) is investigated.

---

---

Mit 1 Abbildung

---

Früher: Alkyliminophosphorsäuretrihalogenide, 1. und 2. Mitt.     

Fake molecular-orbital calculations

The FAKE method of approximate molecular-orbital calculations is presented and illustrated by application to a number of molecules. The method is of the extended Huckel type but uses accurately computed kinetic-energy matrix elements and avoids scale factors of the Wolfsberg—Helmholtz type. It also includes neighbor-atom charge effects and single-center off-diagonal matrix elements. These features permit FAKE occupied-orbital energies and charge distributions to come into close agreement with corresponding ab initio quantities.     

An inequality relating the regulator and the discriminant of a number field

Let K be a number field of degree d with regulator R_K and absolute discriminant D_K. Let r(K) be the rank of the unit group in K, and let p(K) be the maximum of r(k) as k ranges over proper subfields of K. We prove

$\text{R}{}_{\mathrm{K}}\text{> c}{}_{\mathrm{d}}\text{(}\text{log}\text{γ}{}_{\mathrm{d}}\text{D}{}_{\mathrm{K}}\text{)}{}^{\mathrm{r(K)?\rho (K)}}$

for constants c_d, γ_d > 0 depending only on d.     

The molecular structure of norbornene as determined by electron diffraction and microwave spectroscopy

The molecular structure of norbornene has been investigated in the gas phase by combining electron diffraction data with microwave spectroscopic rotational constants. The interatomic distances (r_g) and bond angles were obtained by applying a least squares program to the refined experimental molecular diffraction intensities. The CC bond length was found to be 1.336 ± 0.002 Å while the

) bond length was 1. 529 ± 0.007 Å. Other bond lengths and angles included (IUPAC numbering system was used for norbornene): C₁-C₆ = 1.550 ± 0.020 Å, C₁-C₇ = 1.566± 0.005 Å, C₅-C₆ = 1.556 ± 0.005 Å, C-H_ave. = 1.103 ± 0.003 Å, ∠C₁C₂C₄ = 95.3°. The dihedral angle between planes C₁C₂C₃C₄ and C₁C₆C₅C₄ is 110.8 ± 1.5° while that between C₁C₂C₃C₄ and C₁C₇C₄ is 122.3°. The moments of inertia calculated from ED structure are in good agreement with microwave spectroscopic values.     

Dielectric properties of beryllia ceramics in the near-millimeter wavelength range

We report the refractive indices and absorption coefficients for four beryllia (BeO) ceramic samples. These dielectric properties have been measured over the range from 4 to 18 cm^–1 by use of a Michelson interferometer. The index n, follows the linear relationship n=0.6517 cm³/g×+0.7130 with density, , over the range 2.8<<3.0 g/cm³.     

Stereochemical investigations of a novel class of chiral phosphapalladacycle complexes derived from 1-[(2,5-dimethyl)phenyl]ethyldiphenylphosphine

The phosphapalladacycle derived from 1-(2',5'-dimethylphenyl)ethyldiphenylphosphine has been prepared in the optically active and racemic forms. The phosphine was synthesized as a racemate by the treatment of 1-chloro-1-(2',5'-dimethylphenyl)ethane with sodium diphenylphosphide in THF. The racemic phosphapalladacycle was subsequently obtained as the chloro-bridged dimer by the treatment of the phosphine with palladium(II) acetate followed by anion metathesis with lithium chloride. Alternatively, the phosphine could be optically resolved via metal complexation using (R,R)-bis(mu-chloro)bis{1-[1-(N,N-dimethylamino)ethyl]naphthyl-C(2),N}dipalladium(II) as the resolving agent. An efficient separation of the resulting diastereomeric complexes was achieved by silica gel chromatography. The obtained optically resolved diastereomers were next subject to chemoselective removal of the (R)-N,N-(dimethylamino)-1-(1-naphthyl)ethylaminate auxiliary by treatment with concentrated hydrochloric acid. This process yielded the binuclear dimer complexes containing the resolved eta(1)-P ligand. Cyclopalladation of the coordinated phosphine could next be performed by treatment of its eta(1)-P binuclear dimer with silver(I) hexafluorophosphate(V) in a dichloromethane/water mixture followed by treatment with lithium chloride, giving rise to a pair of optically pure enantiomeric dimers with [alpha](D) -322 and +319 degrees in CH(2)Cl(2). Despite the possibilities of the phosphine to attain a five- membered structure by ortho-palladation or a six-membered ring formation by aliphatic C-H bond activation, only the former was observed. X-ray crystallographic data of the meso dimer and an acetylacetonate derivative indicated that the phosphapalladacycle alpha-C methyl substituent was axially located. The 2-D (1)H-(1)H ROESY spectrum of the acetylacetonate derivative further revealed that the phosphapalladacycle was conformationally rigid in CDCl(3).