Reactions of the Ru3(CO)10(μ-Ph2PCH2PPh2) cluster with enynes RCH=CHC≡CR (R is phenyl or ferrocenyl). Formation of indenone derivatives of triruthenium clusters

The thermal reaction of Ru₃(CO)₁₀(-Ph₂PCH₂PPh₂) (1) with enyne PhCH=CHCCPh afforded the trinuclear ruthenium clusters Ru₃(CO)₆{₃-P(Ph)CH₂PPh₂}{₃-C(Ph)=CHCC(Ph)(1,2-C₆H₄)C(=0)} (2), Ru₃(-H)(CO)₅{₃-P(Ph)CH₂PPh₂}{₃-C(Ph)=CHCC(Ph)(1,2-C₆H₄)C(—0)} (3), and Ru₃(CO)₆(-CO){₃-P(Ph)CH₂PPh₂}{₃-C(C=CPh₂)CH=C(H)Ph} (4) and also two isomers of Ru₃(CO)₅(-CO)(-Ph₂PCH₂PPh₂){₃-C₄Ph₂(CH=CHPh)₂} (5a and 5b). Clusters 2, 3, and 4 were characterized by IR spectroscopy, ¹H and ³¹P NMR spectroscopy, and X-ray diffraction analysis. The reaction of complex 1 with enyne FcCH=CHCCFc gave rise to the Ru₃(CO)₆{₃-P(Ph)CH₂PPh₂}{₃-C(Fc)=CHCC(Fc)(1,2-C₆H₄)C(=0)} (6) and Ru₃(-H)(CO)₅{₃-P(Ph)CH₂PPh₂}{₃-C(Fc)=CHCC(Fc)(1,2-C₆H₄)C(—0)} (7) clusters. According to the spectral data, the latter compounds are isostructural to complexes 2 and 3, respectively.     

Copper diisobutyl-t-butoxyaluminum hydride: A novel reagent for chemoselective reduction of tertiary amides over esters

We demonstrate that copper diisobutyl-t-butoxyaluminum hydride, readily prepared from lithium diisobutyl-t-butoxyaluminum hydride and CuI, effectively and chemoselectively reduces tertiary amides over esters at ambient temperature, affording the corresponding aldehydes in excellent yields.     

Phase Composition of Iron Compounds in the Products of Annealing of the Tertiary Basaltic Rock from Góra Obłoga (the Lower Silesia, Poland)

The work presents results of the research on thermal transformations of iron minerals which are present in basalt rock from Góra Obłoga in Pogórze Złotoryjskie District. The rock under study shows microporphyric texture and compact microstructure and contained: olivine, augite, diopside, plagioclases, serpentines, zeolites, apatite and also opaque minerals (oxides). The basalt was annealing within the temperature range between 573–1473 K, in air, and then, microscopic observations, X-ray diffraction as well as Mössbauer spectroscopy measurements were performed. During the heat treatment of the rock it was found that the content of olivine and augite was gradually decreasing due to progressive oxidation of iron compounds, resulting in formation of magnetite and hematite. The comparison of the results of thermal Mössbauer spectral analysis showed that transformation of iron minerals occurred already under conditions when the basic rock mass underwent only insignificant changes.     

31P CP/MAS NMR of polycrystalline and immobilized phosphines and catalysts with fast sample spinning

Cross‐polarization (CP) at fast magic angle spinning (MAS) frequencies leads to a splitting of the Hartmann–Hahn (HH) matching profile into a centerband and additional bands of higher orders. The matching profiles differ with the substance categories. Therefore, signal intensity is usually lost, when e.g. the routine standard NH₄H₂PO₄ is used for optimizing the ¹H–³¹P HH match prior to measuring phosphines and their metal complexes in polycrystalline or immobilized form. Here, a variety of model compounds, such as Ph₂PCH₂CH₂PPh₂ and (CO)₂Ni(PPh₃)₂, which can be used as ³¹P CP standards for analogous substances or materials are presented. Investigating the influences of MAS frequency, contact time, ¹H pulse power and sample volume on the matching profiles of the model compounds leads to general trends. Thereby, a new strategy for measuring difficult samples with CP at high MAS rates has been developed: their optimum CP parameters are derived from the most intense maxima in the HH matching profiles of the corresponding model compounds. This new strategy is compared with variations of a conventional ramp sequence. Although the latter generally provide smaller signal half‐widths, the new strategy leads to higher signal intensities. The new method was successfully applied to polycrystalline and immobilized phosphines and catalysts. Copyright © 2003 John Wiley & Sons, Ltd.     

Lysozymes: a chapter of molecular biology

Hen egg-white lysozyme was the first enzyme whose tertiary structure could be elucidated. The peptide chain of this enzyme is arranged in two sections, of approximately equal size, that are separated by a deep cleft. Substrates (and inhibitors) are bound in this cleft via hydrogen bonds and are hydrolyzed under the action of Glu 35 and Asp 52, which form the active site of the enzyme. Although the lysozymes, which occur in many species of animals and plants, exhibit differences in their chemical behavior, they have the same qualitative biological activity; quantitatively important differences have been noted which also concern the specificity. Infection of E. coli with bacteriophages gives rise to a lysozyme whose formation is controlled by the phage DNA. The fact that mutated lysozymes are produced when the phages are treated with mutagens opens new fields of research in molecular biology.     

Selective ruthenium-catalyzed double reductive aminations using hydrosilane to access tertiary amines and piperidine derivatives

A highly selective double reductive aminations of aldehydes with anilines to give tertiary amines, in the presence of [RuCl₂(p-cymene)]₂ catalyst and PhSiH₃, was performed under neat conditions. Piperidine derivatives were successfully synthesized by a double reductive amination followed by cyclisation from glutaric dialdehyde with anilines.     

The synthesis of a [2.2]paracyclophane-derived secondary phosphine oxide and a study of its reactivity

A planar chiral secondary phosphine oxide based on [2.2]paracyclophane was synthesized and its chemistry investigated; it was shown to be a competent pre-ligand in palladium(0)-mediated reactions, and displayed promising activity in gold(I)-catalysed cyclisations. The secondary phosphine oxide could be transformed into a collection of P-stereogenic tertiary phosphine oxides. These are rare examples of the planar chirality of [2.2]paracyclophane being combined with a P-stereogenic centre. Unfortunately, epimerisation of the phosphorus stereocentre during reduction limits the use of this chemistry.     

An unusual Mannich type reaction of tertiary aromatic amines in aqueous micelles

An efficient, unusual Mannich type reaction of tertiary aromatic amines, formaldehyde and 1,3-dicarbonyl compounds is described in aqueous micelles catalyzed by boric acid to afford dialkylaminoarylated 1,3-dicarbonyls. In this unusual Mannich type reaction, tertiary aromatic amines react with formaldehyde to generate an N-alkyl-N-(4-methylenecyclohexa-2,5-dienylidene)alkylaminium intermediate (aza quinone methide), which undergoes nucleophilic addition with 1,3-dicarbonyl compounds. The reaction is highly regioselective, and exclusively para functionalized products are formed in high yields.