Elektronegativ substituierte Silane mit β-ständigem Stickstoff-Donor und Kristallstrukturen einfacher Metallalkyle der Gruppe 12:Elektronegativ substituierte Silane mit beta-ständigem Stickstoff-Donor und Kristallstrukturen einfacher Metallalkyle der Gruppe 12

Für eine Reihe industriell eingesetzter Silane ist der alpha-Effekt - die Wechselwirkungen zwischen Silicium und einem geminalen Donorzentrum - von Bedeutung. Durch die Synthese und Untersuchung geeigneter Modellverbindungen konnten alte Postulate zu dieser schwachen Wechselwirkung teils falsifiziert, teils auf eine neue Grundlage gestellt werden

The synthesis of the cyclopenta(a)phenanthren-17-ones and their putative active metabolites.

The rapid and efficient synthesis of the cyclopenta(a) phenanthren-17-one ring system is described. This synthesis features the utilization of a Lewis acid-catalyzed Diels-Alder reaction of 1,2-dihydro-7-methoxy-4-vinylnaphthalene with an $\alpha$-heterosubstituted cyclopentenone derivative, which acted as a cyclopentynone equivalent. The use of 2-phenylselenenyl-2-cyclopentenone and 2-bromo-2-cyclopentenone was investigated; the latter compound proved to be the more efficacious reagent when employed in the presence of tin(IV) chloride. The generality of this reaction was examined using two other diene components: 1,2-dihydro-7-methoxy-4-(2-propenyl)naphthalene and 1,2-dihydro-4-vinylnaphthalene. Reaction conditions were discovered to promote the reaction of the former diene with the utilization of a different catalyst, solvent and reaction temperature. An investigation toward the use of a cuprate addition/Friedel-Crafts cyclization sequence is discussed. The conjugate addition of an aryl cuprate followed by the trapping of the resultant enolate with ethyl bromoacetate led to the stereoselective synthesis of the trans-aryloxocyclopentaneacetic acids. The cyclization of these trans-keto acids was studied, but did not produce any improvement over existing methods. With the cyclopenta (a) phenanthren-17-one skeleton in hand, the synthesis of the putative active metabolites of the mutagen 15,16-dihydrocyclopenta (a) phenanthren-17-one was undertaken. Thus, the first chemical synthesis of the trans-3,4-dihydrodiol derivative is described. This compound was transformed into the syn-diol epoxide derivative, syn-1,2-epoxy-1,2,3,4,15,16-hexahydro-trans-3,4-dihydroxycyclopenta (a) phenanthren-17-one. This is the first isolation of a diol epoxide of a cyclopenta (a) phenanthrene. Some important differences between the previously studied polycyclic aromatic hydrocarbons and these compounds are due to the presence of the ketone; this was the first synthesis of the dihydrodiol and diol epoxide of a molecule bearing a ketone functionality. The protection of this group as the methoxime derivative and its eventual deprotection in the presence of the highly sensitive dihydrodiol function using a low valent titanium reagent played crucial roles in the present synthesis.Ph.D.ChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/105819/1/9208697.pdfDescription of 9208697.pdf : Restricted to UM users only

Trifluoromethylated Compounds with SiNN and SiON Backbone, and the Crystal Structures of Trimethyl- and Trichloro(trifluoromethyl)silane

Woski M, Mitzel NW. Trifluoromethylated Compounds with SiNN and SiON Backbone, and the Crystal Structures of Trimethyl- and Trichloro(trifluoromethyl)silane. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES. 2009;64(1):83-92.The reaction of (F3C)Cl2SiCl3 with the lithiated hydrazine LiN(Me)NMe2 gives the compound (F3C)Cl2SiN(Me)NMe2 (1) and in traces Cl3SiN(Me)NMe2 (2). The reactions with LiN(SiMe3)NMe2 and LiONMe2 give (F3C)Cl2SiN(SiMe3)NMe2 (4) and (F3C)Cl2SiONMe2 (5), respectively. The compounds were characterised by multinuclear solution NMR, gas-phase IR spectroscopy and mass spectrometry. Information about conformational preferences of I and 4 call be extracted by comparing experimental IR spectra with those Calculated by quantum chemical methods (B3LYP/6-311G**). The former show the gas phase of the beta-donor-acceptor silanes 1 and 4 to be dominated by the anti conformations, while the calculations show a preference for the gauche conformers. The crystal structure of Cl3SiN(Me)NMe2 (2) has been determined. The solid-state structures of the Ruppert reagent F3C-SiMe3 (1) and its chlorine analogue F3C-SiCl3 (2) have also been determined by X-ray diffraction of single crystals grown by in situ techniques

Studies on the role of a photon collimator for the ILC positron source.

A positron source based on a helical undulator provides the capability of producing a beam of polarised positrons. The degree of polarisation of the positrons depends upon the polarisation of the photons produced from the undulator; the polarisation of the photons in turn depends on the photon energy and production angle. We calculate the photon energy spectrum and polarisation for one design of the helical undulator for the International Linear Collider (ILC), investigate approximations commonly made in calculating these quantities, and explore the role of a photon collimator in improving the positron polarisation

Synthesis and structure of an aluminium-nitrogen heteronorbornane with bulky (t)butyl substituents and the crystal structure of tri((t)butyl)aluminium

Woski M, Mitzel NW. Synthesis and structure of an aluminium-nitrogen heteronorbornane with bulky (t)butyl substituents and the crystal structure of tri((t)butyl)aluminium. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES. 2004;59(3):269-273.The reaction of bis(lithiomethyl-methylamino)methane with di(t)butylaluminium chloride leads to the formation of 3,3,6,6-tetra-(t)butyl-1,4-dimethyl-3,6-dialumina-1,4-diaza-norbomane by simultaneous formation of two metal-carbon and two metal nitrogen bonds accompanied by two ring closure reactions. The compound was identified by an NMR analysis (H-1, C-13, Al-27) and by determination of its crystal structure. Despite the high steric demand of the (t)butyl groups, the norbornane-basket structure is favoured over potential isomers containing three-membered rings and over polymeric aggregation. The crystal structure of tri((t)butyl)aluminium has been determined. (Bu3Al)-Bu-t crystallizes as a monomer, with the molecules interconnected by weak secondary (AlC)-C-... contacts (2.95 Angstrom) leading to a slight deviation of the AlC3 units from a planar coordination geometry at the Al atoms

Organoaluminium and -gallium compounds with o-oximato substituents

Mitzel NW, Lustig C, Woski M. Organoaluminium and -gallium compounds with o-oximato substituents. ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES. 2003;58(5):363-368.The organoaluminium and -gallium acetonoximates (tBu(2)MON=CMe2)(2) (M=Al, Ga) have been prepared by the reaction of acetoneoxime with tri-tert-butylaluminium and -gallium. The compounds (Me2MON=CMe2)(2) (M=Al, Ga), described previously, were synthesized for comparison. All compounds have been characterised by NMR spectroscopy (H-1, C-13, Al-27), by mass spectrometry and elemental analyses. The crystal structures of the four compounds have been determined, and it was shown that all form dimers with six-membered M2O2N2 rings by aggregation through the imino N atoms. The compounds (Me2MON=CMe2)(2) adopt boat conformations, whereas the compounds (tBu(2)MON=CMe2)(2) prefer chair conformations. Large differences in the M-O-N angles have been found between the methyl and the tert-butyl analogues

Different modes of aggregation in organoaluminium and -gallium hydroxylamides

Mitzel NW, Lustig C, Woski M. Different modes of aggregation in organoaluminium and -gallium hydroxylamides. DALTON TRANSACTIONS. 2004;(3):397-401.The organoaluminium and - gallium hydroxylamides (Me2GaONMe2)(2), (tBu(2)AlONMe(2))(2), (tBu(2)GaONMe(2))(2) and ((Me2AlONPr2)-Pr-i)(2) have been prepared by the reaction of the hydroxylamines Me2NOH and (Pr2NOH)-Pr-i with the trialkylmetal compounds trimethylgallium, tri- tbutylaluminium and tri- tbutylgallium, respectively. All compounds have been characterised by NMR spectroscopy (H-1, C-13, N-15, O-17 and Al-27), by mass spectrometry and elemental analyses. The crystal structures of the four compounds have been determined, showing that they all form dimers but with different modes of aggregation: (Me2GaONMe2)(2) has a Ga2O2N2 six-membered ring, ((Bu2AlONMe2)-Bu-t)(2) and ((Me2AlONPr2)-Pr-i)(2) have Al2O2 four-membered rings, ((Bu2GaONMe2)-Bu-t)(2) forms a Ga2O2N five-membered ring

Crystal structure of 4,4′-dibromo-2′,5′-dimethoxy-[1,1′-biphenyl]-2,5-dione (BrHBQBr)

In the title compound, C14H10Br2O4, the dihedral angle between the aromatic rings is 67.29 (19)°. Both methoxy-group C atoms lie close to the plane of their attached ring [deviations = −0.130 (4) and 0.005 (5) Å]. In the crystal, molecules pack in a centrosymmetric fashion and interact via a mixture of weak π–π stacking interactions [centroid–centoid separations = 4.044 (2) and 4.063 (3) Å], weak C—H...O hydrogen bonding, and Br...Br halogen bonding. This induces a geometry quite different than that predicted by theory

Polarization of charge-transfer bands and rectification in hexadecylquinolinium 7,7,8-tricyanoquinodimethanide and its tetrafluoro analog

A Langmuir-Blodgett (LB) multilayer film of the unimolecular rectifier hexadecyl-gamma-quinolinium-7,7,8-tricyanoquinodimethanide (C(16)H(33)gammaQ-3CNQ) has two distinct polarized charge-transfer bands, one at lower film pressures (28 mN m(-1)) with a peak at 530 nm, due to an intramolecular charge transfer or intervalence transfer (IVT); past the collapse point (32 to 35 mN m(-1)), this band disappears, and a new intermolecular charge-transfer band appears with peak at 570 nm. An LB multilayer film of the tetrafluoro analogue, hexadecyl-gamma-quinolinium-2,3,5,6-tetrafluoro-7,7,8-tricyanoquinodimethanide (C(16)H(33)gammaQ-3CNQF(4)) shows, for all film pressures, only one IVT band with a peak at 504 nm; when sandwiched between gold electrodes, (C(16)H(33)gammaQ-3CNQF(4) is also an LB monolayer electrical rectifier