On the topological classification of pseudofree group actions on 4-manifolds: II

This paper is concerned with the algebraic aspects of the classification of pseudofree, locally linear group actions on a simply connected 4-manifold, particularly with the splitting and stability properties of the associated Hermitian intersection module and its isometry group. Our main result is the proof of stability of the equivariant intersection form for a large class of pseudofree actions. We also prove a topological rigidity theorem stating that two locally linear, pseudofree actions on a closed, oriented, simply connected 4-manifold, with the equivariant intersection forms indefinite and of rank at least 3 at each irreducible character, are topologically conjugate by an orientation preserving homeomorphism if and only if their oriented local representations at the corresponding fixed points are linearly equivalent.Partially supported by the N.S.F.     

Titanium(IV)-mediated synthesis of 2,3-diisothiocyanato-succinic acid diesters and 3,6-dithioxo-piperazine derivatives

Oxidative homocoupling of titanium(IV) enolates of 2-isothiocyanato-carboxylic esters resulted in the synthesis of 2,3-diisothiocyanato-succinic acid diesters. The reactions were carried out using DIPEA/TiCl₄ oxidizing system and led to chiral dimers (instead of meso) as main products. Titanium(IV) enolates derived from hindered 2-isothiocyanato-carboxylates did not undergo the oxidative homocoupling but gave 3,6-dithioxo-piperazines.     

Standardization protocols and optimized precursor sets for the efficient application of automated parallel synthesis to lead optimization: a Mitsunobu example

A strategy has been developed for the efficient application of automated parallel synthesis to specific aspects of the lead optimization processes employed in drug discovery. The method involves the synthesis of collections of compounds using sets of precursors designed to encompass established medicinal chemistry principles and that have been concurrently optimized with respect to a specific chemical transformation. The strategy is illustrated using an automated Mitsunobu protocol employing sets of aliphatic alcohols and phenols as precursors. The former has been formatted to perform simple alkyl homologation exercises, with the latter being designed for use in diversity-based studies.     

Synthesis of Chiral 2,4-Chiral 2,4-Dichloro-6-menthoxy-1,3,5-triazines and 2-Chloro-4, 6-Dimenthoxy-1,3,5-triazines as Enantiodifferentiating Coupling Reagents. An X-ray Study on 2,4,6-Trimenthoxy-1,3,5-triazine

Chiral mono-di-and trimenthoxy-1,3,5-triazines ware obtained from natural menthol and cyanuric chloride and applied as enantioselective coupling reagents in the synthesis of dipeptides.     

Probing the Origin of Adaptive Aromaticity in 16-Valence-Electron Metallapentalenes

Species with adaptive aromaticity are aromatic in the ground and lowest-lying triplet excited states and they have normally intermediate singlet-triplet gaps. Few examples of compounds with adaptive aromaticity are known to date, including 16-valence-electron (16e) metallapentalenes. A sweeping search could be conducted to discover new members of this group, but efficient designs with an explicit strategy would facilitate the quest for new members of this elusive family. Density functional theory calculations and aromaticity evaluations have been performed to reveal the nature of triplet-state aromaticity in 16e metallapentalenes. Our results show that coordination of strong σ- or π-donor ligands helps achieving adaptive aromaticity of 16e metallapentalenes by means of a spin delocalization mechanism. These results have important implications for understanding the unusual properties of the organometallic adaptive aromatics, leading the way to efficient design of new compounds with tunable singlet-triplet gaps.     

Refinement effect of RE in light weight Mg–Li–Al alloys

Journal of Thermal Analysis and Calorimetry - The effect of 2 mass% rare earth elements (RE) as in mischmetal state on the structure, thermal behaviour and mechanical properties of...     

On the low-temperature properties of

Magnetic, electrical transport and heat capacity measurements have been performed on polycrystalline sample of the compound TmRu₂Si₂, which crystallizes with the tetragonal ThCr₂Si₂-type crystal structure. The results show paramagnetic behaviour down to 0.3 K, at variance with the literature data. On the basis of the collected data, possible origins of non-magnetic behaviour are discussed. Mixed valence of Tm ions or hybridisation between Tm 4f and Ru 4d states are the most probable reasons for paramagnetic behaviour of the TmRu₂Si₂.     

Luftuntersuchung

Ohne Zusammenfassung