title: Ultrafast two-dimensional infrared spectroscopy resolves the conformational change of an Evans auxiliary induced by Mg(ClO4)2.
abstract: Structure determination of reactive species is a key step in understanding reaction mechanisms. We demonstrate the application of polarization-dependent two-dimensional infrared spectroscopy (P2D-IR) as a powerful tool combining structure resolution with ultrafast time resolution. We apply this technique to investigate the substrate-catalyst complexes in a Lewis acid catalyzed Diels-Alder reaction. Using Mg(ClO(4))(2) as a Lewis acid, we found that an additional complex besides the chelate typically postulated as reactive species forms. Experimental access to this new species leads to a deeper understanding of the observed selectivities for the Diels-Alder reaction catalyzed by Lewis acids. Our findings are supported by density functional computations at the M06/6-31+G(d,p) level, including solvent corrections.
authors.affiliation: Institute of Biophysics, Johann Wolfgang von Goethe University, Max-von-Laue-Strasse 1, 60438 Frankfurt, Germany.
authors.forename: Andreas T
authors.initials: AT
authors.lastname: Messmer
authors.forename: Sabrina
authors.initials: S
authors.lastname: Steinwand
authors.forename: Katharina M
authors.initials: KM
authors.lastname: Lippert
authors.forename: Peter R
authors.initials: PR
authors.lastname: Schreiner
authors.forename: Jens
authors.initials: J
authors.lastname: Bredenbeck
mesh_terms: D017616:Magnesium Compounds / Q000737:chemistry*; D008968:Molecular Conformation; D010472:Perchlorates / Q000737:chemistry*; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D013997:Time Factors
chemical_list: D017616:Magnesium Compounds; D010472:Perchlorates; C016547:magnesium perchlorate