SIMS and AES measurements on the LaNi5-hydrogen system

Summary SIMS (Secondary Ion Mass Spectrometry) and AES (Auger Electron Spectroscopy) investigations were carried out on polycrystalline LaNi₅ samples and on LaNi₅ samples, which have been loaded with hydrogen electrochemically. AES measurements show an enrichment of obviously oxidized La at the surface, while in the SIMS spectra the emission of negative ions attracts special attention. In contrast to the V-H- and Nb-H-system negative Me_xH_y-ions turned out to be the most sensitive species for hydrogen detection in SIMS experiments on LaNi₅. The emission of negative ions of type Ni_x and Ni_yH_x, which are not observed on pure Ni are due to the electropositive character of La in this special matrix and the presence of hydrogen. The results point to a higher affinity of hydrogen to Ni than to La.     

Methylaluminum complexes based on tridentate 2,6-bis(mercaptoalkyl)pyridine SNS-ligands

New SNS-ligands were obtained by consequent ring-opening of substituted thiiranes by lithiated 2,6-lutidine, mono- functionalized SN-ligands having been isolated as the intermediate compounds. The molecular structure of ligand 2,6-Py(CH₂CH₂CBn₂SH)₂ was elucidated by XRD analysis.The reaction of AlMe₃ with SNS-ligands afforded monomeric methyl aluminum complexes which have been tested in ring- opening polymerization of ε caprolactone in bulk.     

Factors controlling electron transfer reactions and stabilisation of uncommon oxidation states of chromium

Some experimental approaches to seek semi-quantitative understanding of factors controlling outer sphere electron transfer reactions of some transition metal complexes have been made. The relative importance of nuclear and electronic factors to outer sphere processes has been examined. By the manipulation of Franck-Condon or nuclear factors, it has now been possible to gain access into the chemistry of chromium in unusual oxidation states. An example of a reorganisation controlled electron transfer reaction involving Cr(IV)-Cr(III) system has been demonstrated. The bimolecular rate of reduction of diperoxoaquaethylenediamine chromium(IV) and diperoxodiethylenetriamine chromium(IV) is independent of the nature of th reductant employed viz. Fe²⁺ or VO²⁺ indicating that the generation of6 coordinate Cr(IV) species from7 coordinate of diperoxochromium(IV) reactant may be rate limiting. Similarly by increasing the barrier for the6 coordinate to4 coordinate structures through equatorial coordination of macrocyclic ligands, it has now been possible to detect through cyclic voltommogram the formation of relatively stable Cr(IV) species in the electrochemical oxidation of Cr(Me₄[14] tetraene)(H₂O) ₂ ³⁺ in aqueous sulphuric acid media. The kinetics and mechanism of the cerium(IV) and iodosyl benzene oxidation of Cr(salen)(H₂O) ₂ ⁺ and Cr(salprn)(H₂O) ₂ ⁺ have been investigated and kinetic and spectroscopic evidence for the formation of Cr(IV) transients and stable Cr(V) products has been presented. The relative importance of Franck-Condon factors in the oxidation of Cr(III) to Cr(IV) and Cr(V) states in different macrocyclic and multidentate ligand environments has been discussed.     

Polyene cyclization : cyclization studies on an acyclic furanoditerpene and its epoxide

Reaction of an acyclic diterpene alcohol 1c with chlorotrimethylsilane and sodium iodide or SnCl₄ furnishes compounds 7 and 8. This cyclization is reminiscent of the biosynthesis of pallescensins E-G - an analogous compounds in sesquiterpenoids. Reaction of the epoxide 2 with SnCl₄ furnishes only the acyclic compounds 12, 13, 14a, 14 c and 15a. Photolysis of 2 results in the formation of (4+2) photocycloaduct 21.     

Synthesis of trans -N-2-aryl(heteryl)ethenamidines

2-Amino-2-arylethylamides1 carrying electron-donating substituents in thepara position are transformed by hot POC1₃ to the the title compounds2, presumably via iminochlorides 7 and imidazolium derivatives8. Amides lacking this para-substituent give rise to chloroamidines11 under these conditions.m-Methoxyphenethylamide1t and POCl₃ form, besides11f, an isoquinoline derivative3. The involvement of an imidazolium compound8 in the formation of ethenamidines has been verified by the synthesis of2a from10. Reaction of amide1w with PCl₅ in the cold leads to, besides the chloroamidine11c, thecis-ethenamidine12 which equilibrates with thetrans-isomer2o in hot toluene. Thienylethyl urea13 converted by hot POCl₃ to the imidazoline16, while phenylpropylamide17 forms only the iminochloride18a. Contribution No. 752 from Research Centre     

A study of the alkaloids of plants of the genusStephania

Summary Four alkaloids have been isolated from the tubers ofStephania glabra (Roxb.) Miers. (synonymSt. rotunda Lour.) collected in the Democratic Republic of Vietnam:l-tetrahydropalmatine and three previously undescribed bases (A -C₁₉H₁₈O₂N, C - C₂₀H₂₅O₄N, and D -C₂₁H₂₅O₄N).Khimiya Prirodnykh Soedinenii, Vol. 1, No. 6, pp. 392–394, 1965.The substances in this paper are denoted by letters. The novelty of these substances has not been established, which contradicts the rules of this journal. The paper is printed as an exception (Editiorial Board).     

REACTIONS OF DITHIOLETHIONES WITH N,N-DICHLOROAMIDES

Abstract

Dependent on the starting materials and the reaction conditions N,N-dichloroamides Cl₂N-X (X = COaryl, CO₂alkyl, SO₂aryl, SO₂N(alkyl)₂) react with dithiolethiones 1 and 5 to N-(dithiolyliden)amides 2, 6, S-(dithiolylidene)sulfimides 3, thionoxides 7 and dithiolones 4, 8. The mechanisms have been studied.     

The effect of sulfur and selenium substitutents on the regiochemistry of diels-alder reactions

2-Phenylthio-1,3-butadiene (1) and 2-phenylseleno-1,3-butadiene (2) have been generated in situ from their SO₂ adducts and reacted with a series of unsymmetrical dienophiles. The regiochemical results have been analyzed in terms of qualitative perturbation theory.     

Synthesis of 2-Aryl-1H-s-Triazolo[1, 5-a] Benzimidazoles

2-Aroylaminobenzimidazoles (2) have been converted into 1(2-benzimidazolyl)-5-aryl-1H-tetrazoles (4) by treatment with PCl₅ followed by azidation with NaN₃ in aqueous acetone solution. Pyrolysis of 4 in diphenylether yielded 2-aryl-1H-s-triazolo [1,5-a] benzimidazoles (6). The product of benzylation of 6a has been characterised. A reasonable pathway for the formation of 6 from 4 has been suggested.     

Synthesis and properties of a photoreactive transmembrane probe

Phospholipid1, bearing a benzophenone probe constrained in the middle of the double layer, has been synthesized by condensation of the bis (imidazolide)16 with the CdCl₂ - complex of the lysophosphatidylcholine5. It forms photosensitive liposomes and vesicles, alone and with dimyristoylphosphatidylcholine (DMPC).     

The structures of chimganin and chimgin

Summary The roots ofFerula tschimganica Lipsky have yielded two new compounds with the compositions C₁₈H₂₄O₄ (mp 85°C) and C₁₇H₂₂O₃ (mp 155°C), which have been calledchimganin andchimgin. On the basis of their UV, IR, and NMR spectra and the products of alkaline hydrolysis, it has been shown that chimganin is the ester of 4-hydroxy-3-methoxybenzoic acid and chimgin that of 4-hydroxybenzoic acid with (+)-borneol.Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 59–63, January–February, 1972.     

Novel tricyclic terpanes (C19, C20) in sediments and petroleums

Three homologs (1–3 ; C₁₉,C₂₀) of a tricyclic terpane series (C₁₉C₃₀0 widely occuring in sediments and petroleums have been identified as probable degradation products of tricyclohexaprenane 13, a yet unknown tricyclic terpane skeleton.     

Regioselective hydroborations of methylvinylchlorosilanes

The regioselectivity of the hydroboration of the methylchlorovinylsilanes, Cl_nMe_3?nSiCHCH₂ (n= 0 ? 3), has been investigated using BH₃←THF, 9-BBN, disiamyl- and dicyclohexylborane. Methylation of the adducts with methylmagnesium bromide is complicated by formation of tetraalkylboronates. Alkaline hydrogen peroxide oxidation of the boronates gives reasonable yields of the corresponding α- and β-trimethylsilylethanols forn= 0 and 1. Forn= 2 and 3, conversion of the adducts to the corresponding α- and β- deuteroethylsilanes by treatment with excess sodium methoxide in methanol-0-d provides a more effective means of derivatization. Addition of the alkenes,n= 2 or 3, to excess BH₃←THF givesca. 90% of the α-boro-organo-chlorosilanes. For all of the alkenes, the dialkylboranes giveca. 80% of the β-boron adducts.     

Triterpenoids from Rhododendron caucasicum and Rh. ledebourii gas-liquid chromatography of rhododendron extracts

Conclusions FromGentiana olgae have been isolated gentiananine, gentianadine, and the new base gentianaine C₆H₇O₃N. The structural formula for the latter has been given.G. caucasica contains gentianine and gentiananine; andG. kaufmanniana contains gentianine, gentianaine, and gentiananine; gentianaine has been found in the mother liquors fromG. turkestanorum andG. olivieri.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 1, pp. 32–36, 1969     

Synthesis and structure of hexakis (p-hydroxyphenyloxy)benzene: A versatile analogue of the hydrogen-bonded hexameric unit of β-hydroquinone

The title hexaphenol (1), a direct analogue of the -hydroquinone hexameric unit, has been prepared by six-fold demethylation of hexakis (p-methoxyphenyloxy)benzene (2) with BBr₃. Host1 forms a trigonal adduct, space groupR3,a=22.088(3),c=12.232(3) Å, containing 6 molecules of pyridine per host molecule: a detailed X-ray study of this inclusion compound reveals a true clathrate structure, the closed cages of which accommodate a small, non-stoichiometric amount of water.     

Hydroformylation of olefins catalyzed by rhodium complex anchored on clay matrices

Investigations on the catalytic activity of a transient Rh(I) triphenylphosphine complex1 anchored on montmorillonite clay have been carried out with respect to hydroformylation of olefins at 70°C and 60 atm of CO+H₂ (1:1). The analysis has shown that aldehydes and hydrocarbons of the corresponding olefins result under hydroformylation conditions. In limonene, reaction proceeds with double hydroformylation and hydrogenation to give the respective oxo products. The catalytic activities of1 are compared with Wilkinson's Rh^I (H) (CO) (PPh₃)₂ (6) complex in solution under the same hydroformylation conditions.     

Synthesis, characterization and reactivity of oxomolybdenum(V) complexes with ONS and NNS donors

The monomeric oxomolybdenum(V) complexes, [MoOLCl₂]1a-1d [HL = S-benzyl/methyl 3-(2-pyridyl)methylenedithiocarbazate (1a and1b), or N-methyl-S-benzyl/methyl 3-(2-hydroxy phenyl)methylenedithiocarbazate (1c and1d) are synthesized by the reaction of MoOCl ₅ ²⁻ with HL ligands. All these complexes show magnetic moment of about 1.7 B.M. The complexes,1a and1b, exhibit rhombicg-tensor anisotropy (like xanthine oxidase) whilst1c and1d show axial spectrum. The above complexes undergo irreversible electrochemical reduction furnishing Mo(IV) species and the potentials are dependent on the S-substituents. Reactions of MoOX ₅ ⁻ (X = Cl or Br) with H₂L¹ [H₂L¹ = S-methyl 3-(5-R-2-hydroxyphenyl)methylenedithiocarbazate] (R = H, CH₃, Cl, Br) produce complexes of thiolatobridged dimers, [Mo₂O₂L ₂ ¹ X₂], which show sub-normal magnetic moments at room temperature. The metal-centred irreversible oxidation and reduction of these complexes show expected dependence on the R-substituents of the salicyl phenyl ring of the ligands.     

Asymmetric Diels-Alder reaction directed toward chiral anthracycline intermediates

The asymmetric Diels-Alder reaction of naphthoquinone derivative and diene in the presence of chiral boron reagent derived from B(OMe)₃ and ( R, R)(+)-tartaric acid diamide has been described as a model for the enantioselective preparation of important tetracycline natural products.