Martin Klussmann

Bio: Martin Klussmann is an academic researcher from Max Planck Society. The author has contributed to research in topics: Catalysis & Oxidative coupling of methane. The author has an hindex of 29, co-authored 79 publications receiving 3398 citations. Previous affiliations of Martin Klussmann include Imperial College London.

Thermodynamic control of asymmetric amplification in amino acid catalysis

Abstract: Ever since Pasteur noticed that tartrate crystals exist in two non-superimposable forms that are mirror images of one another--as are left and right hands--the phenomenon of chirality has intrigued scientists. On the molecular level, chirality often has a profound impact on recognition and interaction events and is thus important to biochemistry and pharmacology. In chemical synthesis, much effort has been directed towards developing asymmetric synthesis strategies that yield product molecules with a significant excess of either the left-handed or right-handed enantiomer. This is usually achieved by making use of chiral auxiliaries or catalysts that influence the course of a reaction, with the enantiomeric excess (ee) of the product linearly related to the ee of the auxiliary or catalyst used. In recent years, however, an increasing number of asymmetric reactions have been documented where this relationship is nonlinear, an effect that can lead to asymmetric amplification. Theoretical models have long suggested that autocatalytic processes can result in kinetically controlled asymmetric amplification, a prediction that has now been verified experimentally and rationalized mechanistically for an autocatalytic alkylation reaction. Here we show an alternative mechanism that gives rise to asymmetric amplification based on the equilibrium solid-liquid phase behaviour of amino acids in solution. This amplification mechanism is robust and can operate in aqueous systems, making it an appealing proposition for explaining one of the most tantalizing examples of asymmetric amplification-the development of high enantiomeric excess in biomolecules from a presumably racemic prebiotic world.

A Comparative Mechanistic Study of Cu-Catalyzed Oxidative Coupling Reactions with N-Phenyltetrahydroisoquinoline

Abstract: A comparative mechanistic study of Cu-catalyzed oxidative coupling reactions of N-phenyltetrahydroisoquinoline with different nucleophiles was conducted. Two previously reported combinations of catalyst and oxidant were studied, CuCl2·2H2O/O2 and CuBr/tert-butyl hydroperoxide (TBHP). On the basis of a synthetic study with different nucleophiles, the electrophilicity of the intermediate iminium ion was estimated and differences between the two methods were revealed. The key intermediate in the aerobic method is shown to be an iminium ion, formed through oxidation by copper(II), which can react with any nucleophile of sufficient reactivity. The role of oxygen is the reoxidation of the reduced catalyst. In the CuBr/TBHP system, an α-amino peroxide is proposed as a true intermediate within the catalytic cycle, formed from the amine and TBHP by a Cu-catalyzed radical reaction pathway and acting as a precursor to the iminium ion intermediate.

Mechanistic Studies on a Cu-Catalyzed Aerobic Oxidative Coupling Reaction with N-Phenyl Tetrahydroisoquinoline: Structure of Intermediates and the Role of Methanol As a Solvent

Abstract: The mechanism of an aerobic copper-catalyzed oxidative coupling reaction with N-phenyl tetrahydroisoquinoline was investigated. The oxidized species formed from the reaction of the amine with the copper catalyst were analyzed by NMR-spectroscopy. An iminium dichlorocuprate was found to be the reactive intermediate and could be structurally characterized by X-ray crystallography. The effect of methanol to effectively stabilize the iminium ion was investigated and shown to be beneficial in an oxidative allylation reaction.

Catalytic Oxidative Coupling Reactions for the Formation of Carbon-Carbon Bonds without Carbon-Metal Intermediates

Abstract: Oxidative coupling reactions offer an elegant method to forma carbon-carbon bond from two carbon-hydrogenbonds. The ubiquity of carbon-hydrogen bonds in organicmolecules offers the potential to couple simple starting materialsin order to create products of higher complexity in a single stepwithout the formation of unwanted waste products. This article reviewscatalytic oxidative coupling reactions that proceed without theformation of intermediate organometallic species bearing carbon-metalbonds, focusing on key developments and recent publications. 1 Introduction 2 Arenes 2.1 Binaphthols 2.2 Biphenols and Bianilines 2.3 Other Reactions with Arenes 3 Carbonyl and Related Compounds 4 Amines 4.1 Cyanation 4.2 Arylation 4.3 Nitroalkylation 4.4 Coupling with Carbonyl Compounds 5 Amides 6 Ethers 7 Allylic Compounds 8 Hydrocarbons 8.1 Arylation 8.2 Coupling with Carbonyl Compounds 9 Conclusions and Outlook

Autoxidative Carbon–Carbon Bond Formation from Carbon–Hydrogen Bonds

Abstract: Activated benzylic CH2-groups in xanthene (I) or dihydroacridines (IV) undergo acid-catalyzed oxidative coupling towards carbonyl compounds.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Asymmetric catalysis by chiral hydrogen-bond donors.

Abstract: Hydrogen bonding is responsible for the structure of much of the world around us. The unusual and complex properties of bulk water, the ability of proteins to fold into stable three-dimensional structures, the fidelity of DNA base pairing, and the binding of ligands to receptors are among the manifestations of this ubiquitous noncovalent interaction. In addition to its primacy as a structural determinant, hydrogen bonding plays a crucial functional role in catalysis. Hydrogen bonding to an electrophile serves to decrease the electron density of this species, activating it toward nucleophilic attack. This principle is employed frequently by Nature's catalysts, enzymes, for the acceleration of a wide range of chemical processes. Recently, organic chemists have begun to appreciate the tremendous potential offered by hydrogen bonding as a mechanism for electrophile activation in small-molecule, synthetic catalyst systems. In particular, chiral hydrogen-bond donors have emerged as a broadly applicable class of catalysts for enantioselective synthesis. This review documents these advances, emphasizing the structural and mechanistic features that contribute to high enantioselectivity in hydrogen-bond-mediated catalytic processes.