Catalytic epoxidations with peroxides: molybdenum trioxide species as the origin of allylic byproducts

Molybdenum(VI)peroxide species, formed in the reaction of Mo(VI) complexes with peroxides, are able to epoxidize >C=C< double bonds heterolytically. In this study, theoretical and experimental evidence is provided for a kinetically competing reaction reaction of such molybdenum(VI)peroxide species with additional peroxide reagent, leading to molybdenum(VI)trioxide species, which easily decompose into radicals. Under epoxidation conditions, those radicals will reduce the selectivity, due to the formation of allylic byproducts. The involved reaction pathways are characterized by DFT calculations, providing kinetic parameters that are in good agreement with the experimental observations.     

Synthese neuer `Push‐Pull'‐Enine

Synthesis of Novel `Push‐Pull'‐Enynes `Push‐pull' enynes 14a – d with EtO, PhO, PhS, and MeS groups as π‐donors have been synthesized by catalyzed coupling of stannyl ynamines 10 with 3‐iodoprop‐2‐enal (Scheme 4).     

Synthese und 1H-NMR-Analyse von Triafulvalen-Vorstufen

Synthesis and ¹ H-NMR Analysis of Triafulvalene Precursors . An attractive concept for the synthesis of triafulvalene ( 1 ) by retro-Diels-Alder reaction (RDA reaction) of precursors 4 and 5 is presented. Both precursors are available in two steps by dibromocarbene addition to dibenzobarrelene ( 8 → 9 ) and barrelene ( 10 → 11 ), followed by CuCl₂-induced formal `carbene dimerization' ( 9 → 4 and 11 → 5 , respectively). Thermal-fragmentation experiments of triafulvalene precursor 4 were unsuccessful, mainly due to the very low volatility of 4 . Spectral parameters of the complex ¹H-NMR spectrum of 3,3′-bi(tricyclo[3,2,2,0^2,4]nona-6,8-dienylidene) ( 5 ) have been determined by analysis of subspectra generated by selective H,H-decoupling experiments followed by iteration/simulation sequences.     

Polymerisierbare Ferrocene: Versuche zur Synthese von Polyferrocenen und Polyferrocenophanen

Polymerizable Ferrocenes: Synthetic Attempts towards Polyferrocenes and Polyferrocenophanes The novel polymerizable ferrocenes 8 (Scheme 2) and 11 (Scheme 3) have been synthesized, and cationic polymerization experiments towards bridged poly(1,1′-diisopropenyl)ferrocenes 1 as well as poly(1,1′,3,3′-tetraisopropenyl)ferrocenes 2 are discussed. In both cases, only oligomeric products with M¯_n ca. 1700/M¯_w of ca. 2900 ( 1 ) and M¯_n ca. 1400/M¯_w of ca. 4000 ( 2 ) have been isolated. On the other hand, synthetic attempts towards polyferrocenophanes 3 (Scheme 6) result in oligomeric products as well.     

Rearrangement of 5-Substituted 5-Aminopentadienals

Strong nucleophiles are needed for inducing ring opening 3 → 4 since the pyrylium salt intermediates 3 , formed from 5-X-substituted 5-aminopenta-2,4-dienals 2 upon treatment with acid, are quite unreactive due to “aromatic” stabilization. However, this allows an easy access to a variety of 2-aminopyrylium salts 3 from “push–pull” enynes 1 . X=OAc, F, Cl, Br, I, OPh.     

The Marcinkiewicz-Zygmund law of large numbers on the group of Euclidean motions and the diamond group

An analogue of the Marcinkiewicz-Zygmund strong law of large numbers is proved for the group of Euclidean motions and for the diamond group. Proceedings of the Seminar on Stability Problems for Stochastic Models, Moscow, Russia, 1996, Part. I.     

Festkörper-Polymerisation eines ‘Push-Pull’-Diacetylens

Solid-State Polymerisation of a ‘Push-Pull’-Diacetylene Solid-state polymerisation of ‘push-pull’-diacetylene 5-(diphenylamino)-1-phenylpenta-2,4-diyn-1-one ( 1d ), initiated by heating of crystals of 1d at 90°, gives ‘push-pull’ poly-diacetylene 2d . X-Ray results and spectroscopic data of monomer 1d as well as of polymer 2d are discussed.