SERMACS 2009 - Simposia Information

Current Interdisciplinary Trends in Organic Chemistry

Organizer: Dr. Waldemar Adam, phone number, fax: 787-756-8242, e-mail: wadam@chemie.uni-wuerzburg.de

Abstracts

Oxidation Catalysis by Hydrogen Bonding

A. Berkessel
aDepartment of Chemistry, Cologne University, Greinstrasse 4, D-50939 Cologne, Germany.
e-mail: berkessel@uni-koeln.de

The lecture summarizes our mechanistic studies in three areas of metal-free and metal-based catalytic oxidation, using hydrogen peroxide as the terminal oxidant.

(1) Epoxidation of olefins[1] and Baeyer-Villiger oxidation of ketones[2], catalyzed by fluorinated alcohols
(2) Asymmetric epoxidation of enones, catalyzed by short amino acid oligomers[3]
(3) Asymmetric epoxidation of olefins, catalyzed by chiral Ti-salalen complexes[4,5]

In all cases, activation of the oxidant/the substrate by hydrogen-bonding networks plays a crucial role: Fluorinated alcohols form H-bond networks which catalyze oxygen transfer from hydrogen peroxide to the substrate olefin (left); enone epoxidation by helical peptides is effected by hydrogen bonding to the catalyst's N-terminus (right); the epoxidation of olefins by Ti-salalen complexes was discovered by Katsuki et al. and reported to rely on activation of a Ti-peroxo species by an intramolecular NH-O bond.4 In the latter case, we investigated the activation and degradation pathways of the Ti-salalen catalyst.[5,6]

References:
1. Berkessel, A.; Adrio, J. A. J. Am. Chem. Soc. 2006, 128, 13412-13420.
2. Berkessel, A.; Andreae, M. R. M.; Schmickler, H.; Neudörfl, J. Angew. Chem. Int. Ed. 2002, 41, 4481-4484.
3. Berkessel, A.; Koch, B.; Toniolo, C.; Rainaldi, M.; Broxterman, Q. B.; Kaptein, B. Biopolymers: Pept. Sci. 2006, 84, 90-96.
4. Sawada, Y.; Matsumoto, K.; Katsuki, T. Angew. Chem. Int. Ed., 2007, 46, 4559-4561.
5. Berkessel, A.; Brandenburg, M.; Leitterstorf, E.; Frey, J.; Lex, J.; Schäfer, M. Adv. Synth. Catal. 2007, 349, 2385-2391.
6. Berkessel, A.; Brandenburg, M.; Schäfer, M. Adv. Synth. Catal. 2008, 350, 1287-1294.

Acknowledgements: Financial support by the Deutsche Forschungsgemeinschaft (DFG) and by the Fonds der
Chemischen Industrie is gratefully acknowledged.

Chemiluminescence: Mechanisms and Applications

Wilhelm J. Baader
Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, 05508-900, São Paulo, SP, Brazil – wjbaader@iq.usp.br.

Bioluminescence (BL), emission of visible light by living organisms, and chemiluminescence (CL), light emission originated from a chemical transformation, are long-known phenomena and several reaction mechanisms are discussed to rationalize excited state formation. Many of the most efficient BL and CL transformations are thought to involve one or more electron transfer steps and chemiexcitation occurs by radical pair or biradical annihilation.[1]  Several BL and CL transformations have been utilized for a vast variety of analytical applications, ranging from glucose determination and HIV immunoassays, highly sensitive transition metal quantification, antioxidant capacity determination and peroxide quantification to the verification of oxidative stress in several cell types in vitro and in vivo.
In this lecture, a brief introduction to the main known general chemiexcitation mechanisms will be given, followed by the description of recent results on the mechanistic elucidation of efficient CL systems as the peroxyoxalate reaction, the induced decomposition of phenoxy-substituted 1,2-dioxetanes and the catalyzed decomposition of new 1,2-dioxetanones (a-peroxylactones). Furthermore, some representative examples for the analytical application of CL reactions will be given, including the use of luminol as a sensitive assay system for antioxidant capacity determination.
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[1] Baader W. J., Stevani C. V., Bastos E. L., “Chemiluminescence of Organic Peroxides”, in: The Chemistry of Peroxides, Chapter 16, p. 1211, ed. Rappoport, Z., Wiley & Sons Ltd, Chichester, 2006.

Catalysts design for environmentally friendly chemical processes

Avelino Corma
Instituto de Tecnología Química (UPV-CSIC), Avda. de los Naranjos, s/n; 46022 Valencia (Spain); acorma@itq.upv.es

Catalysis has directly implication on energy savings and sustainability. When more active and selective will be the catalyst the higher will be the reaction rate (energy saving) and will make a better use of the raw materials. While minimizing the amount of residual products. In other words, well designed environmentally friendly catalysts will help to: a) reduce the consumption of reactants and energy; b) Replace dangerous materials and processes, while looking for alternatives to non suitable reactants; c) Recycle or ecofriendly elimination of residual unwanted products.
It will be presented that molecularly designed environmentally friendly solid catalysts with well defined and isolated active sites, can replace existing chemical processes in where either the present catalyst or the reactants are either unfriendly ecologically or dangerous. More specifically will discuss process with industrial interest in the field of acid catalysis oxidations.
As a second alternative will show the possibility of preparing solid multifunctional catalysts that allow to transform multistep chemical process into a one pot process, avoiding separation and purification steps and reducing the E factor of the process (Kg subproducts / Kg of desired product) by one order of magnitude.
In the last part of the talk will referee to sustainable chemical process by presenting catalytic process to transform biomass and CO2 into chemicals.