Photoinduzierte Cycloadditionen von 3-Benzyl-2H-azirin

Irradiation of 2-azido-3-phenyl-propene ( 5 ) in pentane or benzene solution with a high pressure lamp (pyrex filter) yields 3-benzyl-2H-azirin ( 6 ), which on further irradiation behind quartz or vycor in the presence of trifluoroacetic acid methylester or carbon dioxide yields 4-benzyl-5-methoxy-5-trifluoromethyl-3-oxazolin ( 8 ) and 4-benzyl-3-oxazolin-5-one ( 9 ), respectively (scheme 2). A small amount of 3-phenylacetonitrile is also formed.     

Cumulative indices for Spectrochima Acta, Part A and Spectrochimica Acta, Part B

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), a section of Spectrochimica Acta, Part B (SAB). The hardcopy text is accompanied by an electronic archive, stored on the SAE homepage at http://www.elsevier.nl/locate/sabe. The archive contains data, index and program files. The main article discusses the bibliographical purpose of the program and data files. A collective index for Spectrochimica Acta for volumes since it was split into Parts A and B, and continuing through 1991 for SAA and 1997 for SAB, is presented in DBF format, along with rudimentary data entry and access software.     

The preparation of copper(II) and copper(I) salts in acetonitrile using group VA and VB pentafluorides

Copper(II) fluorine reacts with the pentafluorides, TaF₅, PF₅, and AsF₅, in acetonitrile to give solvated Cu^II, hexafluoroanion salts. These react with copper metal to give the corresponding Cu^I compounds. Similar reactions occur between AsF₅ and silver(I) or thallium(I) fluorides, but silver(II) fluoride reacts with MeCN, and Ag^I hexafluoroarsenate is formed. PF₅ oxidises Cu slowly in MeCN to give Cu^I hexafluorophosphate, but AsF₅ has no oxidising ability towards metals in MeCN. Spectroscopic data for Cu(MF₆)₂·5MeCN and Cu(MF₆)·4MeCN (M = Ta or P) are discussed.     

Cleavage of benzyltrimethylstannanes by aqueous methanolic perchloric acid

The rates of cleavage of some XC₆H₄CH₂SnMe₃ bonds by aqueous-methanolic perchloric acid have been measured spectrophotometrically, and the rate of cleavage of the MeSn bonds of PhCH₂SnMe₃ and Me₄Sn by monitoring the methane evolution. The results indicate that for X = H, p-Me, o-Me, p-Bu^t, o-, m- and p-F and -Cl, and o-Br, the cleavage of the CH₂SnMe₃ bond involves attack of the acid at the benzylic atom, and is not much faster than that of the SnMe bonds, but that a mechanism involving ring-protonation is important for X = m-Me, and greatly predominant for X = m-OMe.     

Longitudinal (1)H relaxation optimization in TROSY NMR spectroscopy

A general method to enhance the sensitivity of the multidimensional NMR experiments performed at high-polarizing magnetic field via the significant reduction of the longitudinal proton relaxation times is described. The method is based on the use of two vast pools of "thermal bath" 1H spins residing on hydrogens covalently attached to carbon and oxygen atoms in 13C,15N labeled and fully protonated or fractionally deuterated proteins to uniformly enhance longitudinal relaxation of the 1HN spins and concomitantly the sensitivity of multipulse NMR experiments. The proposed longitudinal relaxation optimization is implemented in the 2D [15N,1H]-LTROSY, 2D [15N,1H]-LHSQC and 3D LTROSY-HNCA experiments yielding the factor 2-2.5 increase of the maximal signal-to-noise ratio per unit time at 600 MHz. At 900 MHz, the predicted decrease of the 1HN longitudinal relaxation times can be as large as one order of magnitude, making the proposed method an important tool for protein NMR at high magnetic fields.     

Selective Transport of Lead(II) and Strontium(II) Through a Crown Ether-Based Polymer Inclusion Membrane Containing Dialkylnaphthalenesulfonic Acid

New polymer inclusion membranes (PIMs) containing 18-membered crownethers and dialkylnaphthalenesulfonic acid are proposed for Sr2+ and Pb2+removal from nitric acid solutions. The influence of source phasecomposition and stripping agents was characterized and permeabilitycoefficients were calculated. The PIMs are easy to prepare and may be usefulin separation and concentration procedures for these cations from complexmixtures such as nuclear waste. Long-term stability was obtained for atleast several weeks of constant use during which no significant change ofpermeability was observed.     

Preparation of polar phase coated open tubular columns for steroid analysis

Summary Open tubular columns made of soda glass may be successfully coated with polar stationary phases after etching with dry HCl. Such columns are useful in difficult separations of steroids and their subsequent identification.     

Reaction of Tetracopper(I)-Phosphonitocavitand with PhSeSiMe3: Synthesis and Structure of a Polyanionic Cluster [pyH]6[(CuCl)9(μ3-SePh)5(μ4-SePh)]

Treatment of tetracopper(I)-phosphonitocavitand [1·Cu₄(μ-Cl)₄(μ₄-Cl)] (2) (1 = tetraphosphonitocavitand [rccc-2,8,14,20-tetrakis-(iso-butyl)-phosphonitocavitand (C₄₄H₄₈O₈P₄Ph₄)]) with PhSeSiMe₃ in THF at low temperature afforded a novel polyanionic cluster [pyH]₆[(CuCl)₉(μ₃-SePh)₅(μ₄-SePh)] (4) as a major product along with a new tetracopper(I)-phosphonitocavitand (3) with a centered μ₃-Cl. Molecular structure of anionic cluster in 4 consists of six PhSe⁻ bridging ligands containing five μ₃-SePh and one exceptional μ₄-SePh bridging nine copper atoms, of which eight copper atoms have trigonal coordination geometry and the other has distorted tetrahedral geometry. Dedicated to Professor Han-Qin Liu on the occasion of his 70th birthday.     

Alkaloids of a new type fromSophora alopecuroides L.

Summary The structures of aloperine and allylaloperine (fromSophora alopecuroides L.) — alkaloids of a new structural type for the genusSophora — have been established by chemical and spectral methods. A number of parameters, NMR spectra, and mass spectra characterizing this class of compounds has been obtained. The partial synthesis of allylaloperine has been performed.All-Union Scientific-Research Institute of Medicinal Plants. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 30–37, January–February, 1975.     

Biomimetic cycloaddition approach to tropolone natural products via a tropolone ortho-quinone methide

[reaction: see text] A study toward a possible biomimetic hetero Diels-Alder reaction is reported between humulene and a novel tropolone ortho-quinone methide. A suitable tropolone ortho-quinone methide precursor has been prepared from 3-methyl-2-furoate. Heating the ortho-quinone methide precursor gave a tropolone ortho-quinone methide, which in the presence of humulene underwent a hetero Diels-Alder reaction to give a deoxy analogue of epolone B.