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Forschungsschwerpunkt:  

Lehrstuhl für Organische Chemie II
Am Hubland, 97074 Würzburg
Mail: adam@chemie.uni-wuerzburg.de
Url: http://www.organik.chemie.uni-wuerzburg.de

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Forschungsschwerpunkte (und Projekte auf Basis der Grundausstattung):
Photochemische Generierung und mechanistische Aspekte von Reaktionsintermediaten:

Unsere Forschungsinteressen auf dem Gebiet der Photochemie betreffen kurzlebige Reaktionsintermediate, wie z.B. Monoradikale, 1,3-Cyclopentandiyl-Typ und kreuzkonjugierte (non-Kekulé-Typ) Triplett- und Singulett-Diradikale, Polyradikale, Radikalkationen, Radikalanionen sowie elektronisch angeregte Zustände, die vorwiegend photochemisch ( einige Intermediate auch thermisch und chemisch) aus Azoalkanen und gespannten Kohlenwasserstoffen (Hausanen) generiert werden. Die chemischen, physikalischen und spektroskopischen Eigenschaften photochemisch oder chemisch generierter Transienten werden eingehend untersucht. Die Erforschung des chemischen Verhaltens von 1,3-Radikalkationen, die durch photochemische (PET) oder chemische (CET) Elektronentransfer-Prozesse erzeugt werden, stellt einen der wesentlichen Forschungsschwerpunkte auf diesem Gebiet dar.

Ergebnisse:
Für die Ergebnisse dieses Forschungsschwerpunts siehe folgende Publikationen:


767. Adam, W.; Emmert, O.; Heidenfelder, T. The EPR-Spectral D Parameter of Photochemically Generated Cyclopentane-1,3-diyl Triplet Diradicals as a Quantitative Measure of Spin Delocalization in Vinyl-, Phenyl- and Carbonyl-Substituted Radicals, J. Org. Chem. 1999, 64, 3417-3421.

768. Adam, W.; Nikolaus, A.; Sauer, J. Influence of Bridgehead Substitution and Ring Annelation on the Photophysical Properties of Polycyclic DBO-Type Azoalkanes, J. Org. Chem. 1999, 64, 3695-3698.

777. Kita, F.; Adam, W.; Jordan, P.; Nau, W. M.; Wirz, J. 1,3-Cyclopentanediyl Diradicals: Substituent and Temperature Dependence of Triplet-Singlet Intersystem Crossing, J. Am. Chem. Soc. 1999, 121, 9265-9275.

778. Adam, W.; Garcia, H.; Marti, V.; Moorthy, J. N. Homolytic Substitution (SH2) versus Triplet Diradical (ISC) in the Photochemical Denitrogenation of a DBH Azoalkane: Temperature-Dependent syn/anti Diastereoselectivity as a Mechanistic Probe for the Doubly-Inverted Housane, J. Am. Chem. Soc. 1999, 121, 9475-9476.

782. Adam, W.; Heidenfelder, T. Regio- and Diastereoselective Rearrangement of Cyclopentane-1,3-diyl Radical Cations Generated by Electron Transfer, Chem. Soc. Rev. 1999, 28, 359-366.

783. Adam, W.; Barneveld van, C.; Gerke, J.-S.; Klärner, F. G. The EPR D-Parameter of 1,3-Diarylcyclopentane-1,3-diyl Triplet Diradicals as a Probe for Steric Substituent Effects in Benzyl-Type Radicals, J. Chem. Soc., Perkin Trans. 2 1999, 2723-2728.

784. Blancafort, L.; Adam, W.; González, D.; Olivucci, M.; Vreven, T.; Robb, M. A. Theoretical Study of the 1,2 Rearrangement of Housane Radical Cations: Key Role of a Transient Cyclopentane-1,3-diyl Intermediate, J. Am. Chem. Soc. 1999, 121, 10583-10590.

785. Adam, W.; van Barneveld, C. The Importance of Spin Polarization in Electronic Substituent Effects of the Zero-Field EPR D Parameter in 1,3-Diarylcyclopentane-1,3-diyl Triplet Diradicals, J. Am. Chem. Soc. 1999, 121, 10820-10827.

789. Adam, W.; Nikolaus, A. Photoreduction of Polycyclic DBO-Type Azoalkane with Amines to Hydrazine Products, J. Am. Chem. Soc. 2000, 122, 884-888.

792. Abe, M.; Adam, W.; Heidenfelder, T.; Nau, W. M.; Zhang, X. Intramolecular and Intermolecular Reactivity of Localized Singlet Diradicals: The Exceedingly Long-Lived 2,2-Diethoxy-1,3-diphenylcyclopentane-1,3-diyl, J. Am. Chem. Soc. 2000, 122, 2019-2026.

794. Adam, W.; Barneveld van, C.; Emmert, O. The EPR D Parameter as a Measure of Spin Delocalization in 1,3-Cyclopentanediyl Triplet Diradicals with Extendedly Conjugated -Type Substituents, J. Chem. Soc.; Perkin Trans. 2 2000, 4, 637-641.

803. Adam, W.; Peters, K. Peters, E.-M.; Stegmann, V. R. Hydroxy-Directed Regio- and Diastereoselective [2+2] Photocycloaddition (Paternò-Büchi Reaction) of Benzophenone to Chiral Allylic Alcohols, J. Am. Chem. Soc. 2000, 122, 2958-2959.

804. Adam, W.; Garcia, H.; Marti, V.; Moorthy, J. N.; Peters, K.; Peters, E.-M. Photochemical Denitrogenation of Norbornene-Annelated 2,3-Diazabicyclo[2.1.1]-hept-2-ene-Type Azoalkanes: Crystal-Lattice versus Zeolite-Interior Effects, J. Am. Chem. Soc. 2000, 122, 3536-3537.

812. Adam, W.; Marti, V.; Sahin, C.; Trofimov, A. V. Viscosity-Controlled Stereoselective Inversion in the Photochemical Denitrogenation of a Stereolabeled Diazabicyclo[2.2.1]heptene (DBH)-Type Azoalkane, J. Am. Chem. Soc. 2000, 122, 5002-5003.

816. Abe, M.; Adam, W.; Ino, Y.; Nojima, M. Stereochemical Deuterium Labeling as Mechanistic Probe for Differentiating the Singlet- and Triplet-Diradical Spin States in the Rearrangement of the 2-Spiroepoxy-1,3-cyclopentanediyl to Oxetanes, J. Am. Chem. Soc. 2000, 122, 6508-6509.

817. Adam, W.; Baumgarten, M.; Maas, W. A Hydrocarbon Hexaradical with Three Localized 1,3-Cyclopentanediyl Triplet Diradicals Linked by 1,3,5-Trimethylenebenzene as Ferromagnetic Coupler: Synthesis of the Azoalkane Precursor, Photochemical Generation of the Polyradical and EPR Characterization of Its Septet-Spin Ground State, J. Am. Chem. Soc. 2000, 122, 6735-6738.

821. Adam, W.; Emmert, O. The D Parameter of Vinyl-Substituted 1,3-Cyclopentanediyl Triplet Diradicals as a Sensititve Tool to Determine Electronic Substituent Effects in Allylic Radicals, J. Org. Chem. 2000, 65, 4127-4130.

828. Adam, W.; Matsumoto, M.; Trofimov, A. V. Viscosity Dependence of the Chemically Induced Electron-Exchange Chemiluminescence Triggered from a Bicyclic Dioxetane, J. Am. Chem. Soc. 2000, 122, 8631-8634.

829. Adam, W.; Emmert, O. Steric Influence of E- or Z-Monosubstituted and Terminally Disubstituted Vinyl Groups in Matrix-Isolated Cyclopentane-1,3-diyl Triplet Diradicals as Probed by the Zero-Field EPR D Parameter, J. Org. Chem. 2000, 65, 5664-5667.

834. Adam, W.; Trofimov, A. The Effect of meta versus para Substitution on the Efficiency of Chemiexcitation in the Chemically Triggered Electron-Transfer-Initiated Decomposition of Spiroadamantyl Dioxetanes, J. Org. Chem. 2000, 65, 6474-6478.

837. Adam, W.; Maas, W. EPR-Spectral Determination of Electronic Substituent Effects on the D Values of Hydrocarbon Polyradicals (Quintet and Septet Spin States) Composed of Localized 1,3-Cyclopentanediyl Spin-Carrying Units Linked by 1,3-Di- and 1,3,5-Trimethylenebenzene Ferromagnetic Couplers, J. Org. Chem. 2000, 65, 7650-7655.

839. Uppili, S.; Marti, V.; Nikolaus, A.; Jockusch, S.; Adam, W.; Engel, P. S.; Turro, N. J.; Ramamurthy, V. Heavy-Cation-Induced Phosphorescence of Alkanones and Azoalkanes in Zeolites As Hosts: Induced S1 (n*) to T1 (n*) Intersystem Crossing and S0 to T1 (n*) Absorption, J. Am. Chem. Soc. 2000, 122, 11025-11026.

842. Adam, W.; Maas, W.; Nau, W. M. Wavelength-Selective Photodenitrogenation of Azoalkanes to High-Spin Polyradicals with Cyclopentane-1,3-diyl Spin-Carrying Units and their Photobleaching: EPR/UV Spectroscopy and Product Studies of the Matrix-Isolated Species, J. Org. Chem. 2000, 65, 8790-8796.

844. Adam, W.; Diedering, M. The Generation, Detection and Chemical Fate of 1,3-Cyclopentanediyl Radical Cations. In Atualidades de Fisico-Quimica Organica, 1999; Humeres, E., Ed.; Univ. Fed. St. Catarina: Florianopolis, Brazil, 2000; Vol. 12, pp 15-34.

854. Adam, W.; Stegmann, V. R.; Weinkötz, S. Unusual Temperature-Dependent Diastereoselectivity in the [2+2] Photocycloaddition (Paternò-Büchi Reaction) of Benzophenone to cis- and trans-Cyclooctene through Conformational Control, J. Am. Chem. Soc. 2001,123, 2452-2453.

857. Adam, W.; Marti, V.; Sahin, C.; Trofimov, A. V. Stereoselective Formation of Inverted Housane in the Denitrogenation of the Diazenyl Diradical Photolytically Derived from a Stereolabeled Diazabicyclo[2.2.1]hept-2-ene with Bridgehead Substituents as a Function of Solvent- and Temperature-Varied Viscosity, Chem. Phys. Lett. 2001, 26-32.

859. Adam, W.; Stegmann, V. Hydroxy-Group Directivity in the Regioselective and Diastereoselective [2+2] Photocycloaddition (Paternò-Büchi Reaction) of Aromatic Carbonyl Compounds to Chiral and Achiral Allylic Substrates: The Preparation of Oxetanes with up to Three Stereogenic Centers as Synthetic Building Blocks, Synthesis 2001, 8, 1203-1214.

863. Adam, W.; Grüne, M.; Diedering, M.; Trofimov, A. V. Temperature and Viscosity Dependence in the Stereoselective Formation of Inverted Housane for the Photochemical Nitrogen Loss from the Deuterium-Stereolabeled Parent Diazabicyclo[2.2.1]hept-2-ene, J. Am. Chem. Soc. 2001, 123, 7109-7112.

871. Adam, W.; Diedering, M.; Trofimov, A. V. Pressure Dependence of the Stereoselectivity in the Photodenitrogenation of Diazabicyclo[2.2.1]hept-2-ene in Supercritical Fluids: Evidence for the Diazenyl Diradical, Chem. Phys. Lett. 2001, 350, 453-458.

874. Adam, W.; Librera, C. P. The Rearrangement of Annelated Housanes to Triquinane-Like Hydrocarbons by Electron Transfer (1,3-Cyclopentanediyl Radical Cations) and Acid Catalysis (Cyclopentyl Carbenium Ions), J. Org. Chem. 2002, 67, 576-581.

878. Adam, W.; Diedering, M.; Trofimov, A. Solvent Effects in the Photodenitrogenation of the Azoalkane Diazabicyclo[2.2.1]hept-2-ene: Viscosity- and Polarity-Controlled Stereoselectivity in the Housane Formation from the Diazenyl Diradical, Phys. Chem. Chem. Phys. 2002, 4, 1036-1039.

885. Adam, W.; Stegmann, V. Unusual Temperature Dependence in the cis/trans-Oxetane Formation Discloses Competitive syn versus anti Attack for the Paternò-Büchi Reaction of Triplet-Excited Ketones with cis and trans Cylooctenes. Conformational Control of Diastereoselectivity in the Cyclization and Cleavage of Preoxetane Diradicals, J. Am. Chem. Soc. 2002, 124, 3600-3607.

888. Adam, W.; Diedering, M; Trofimov, A. V. Photochemical versus Thermal Skeletal Inversion: Viscosity-Controlled Photodenitrogenation of a Bridgehead-Substituted DBH-Type Azoalkane and Thermal syn-to-anti Housane Isomerisation, J. Am. Chem. Soc. 2002, 124, 5427-5430.

890. Abe, M.; Adam, W.; Hara, M.; Hattori, M.; Majima, T.; Nojima, M.; Tachibana, K.; Tojo, S. On the Electronic Character of Localized Singlet 2,2-Dimethoxycyclopentane-1,3-diyl Diradicals: Substituent Effects on the Lifetime, J. Am. Chem. Soc. 2002, 124, 6540-6541.

891. Márquez, F.; Marti, V.; Palomares, E.; Garcia, H.; Adam, W. Observation of Azo-Chromophore Fluorescence and Phosphorescence Emissions from DBH by Applying Exclusively the Orbital Confinement Effect in Siliceous Zeolites Devoid of Charge-Balancing Cations, J. Am. Chem. Soc. 2002, 124, 7264-7265.

892. Adam, W.; Ortega Schulte, C. M. Spin Delocalization in 1-Heteroallyl Monoradicals as a Measure of Radical Stabilization by Heterovinyl Substituents, Assessed through the EPR-Spectral Zero-Field D Parameter of 1,3-Cyclopentanediyl Triplet Diradicals, J. Org. Chem. 2002, 67, 4569-4573.

900. Adam, W.; Librera, C. P.; Trofimov, A. V. Viscosity-Controlled, Product-Selective Rearrangement of the Cyclopentane-1,3-diyl Radical Cation Derived from an Annelated Housane by Electron Transfer: A Case of Curtin-Hammett Behavior, J. Am. Chem. Soc. 2002, 124, 11936-11939.

902. Adam, W.; Garcia, H.; Diedering, M.; Marti, V.; Olivucci, M.; Palomares, E. Stereochemical Memory in the Temperature-Dependent Photodenitrogenation of Bridgehead-Substituted DBH-Type Azoalkanes: Inhibition of Inverted-Housane Formation in the Diazenyl Diradical through the Mass Effect (Inertia) and Steric Hindrance, J. Am. Chem. Soc. 2002, 124, 12192-12199.

906. Adam, W.; Librera, C. P.; Klärner, F.-G.; Wurche, F. Stereochemical Memory in the Regioselective and Diastereoselective Rearrangement of Tricyclo[3.3.0.02,4]octanes (Housanes) by Electron Transfer 1,3-Cyclopentanediyl Radical Cations), Acid (Cyclopentyl Carbenium Ions) and Silver(I)-Ion Catalysis, J. Am. Chem. Soc. ASAP.

Auszeichnungen und Preise:
Prof. W. Adam: Gastprofessur, Universität Santiago, Spanien, 1999, Universität Bilbao, Spanien, 2000, Universität Ljubljana, Slovenien, 2001und Universität de Ros Andes, La Paz, Bolivien, 2002; Mitglied der Bayerischen Akademie der Wissenschaften, 2001.
Herr V. Stegmann: Internationaler Studentenferienkurs der Firma BASF, 2000.
Herr M. Diedering: Internationaler Studentenferienkurs der Firma BASF, 2001.
Dr. V. Marti: Marie-Curie Stipendium der EU, 1998-1999.
Dr. M. C. Sajimon: Alexander-von-Humboldt Stipendium, 2001-2002.
Dr. A. V. Trofimov: Academia Europaea Prize (Young Scientists Award in Chemistry), 1999.

Ausstattung:
Argonionen-Laser, EPR- Spektrometer, Fluoreszenz-Spektrometer , GC, MS, NMR- Spektrometer (600-, 400-, 250- und 200-MHz), UV-Spektrophotometer.

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Weitere Publikationen