title: Functionality, Effectiveness, and Mechanistic Evaluation of a Multicatalyst-Promoted Reaction Sequence by Electrospray Ionization Mass Spectrometry.
abstract: A multicatalytic three-step reaction consisting of epoxidation, hydrolysis, and enantioselective monoacylation of cyclohexene was studied by using mass spectrometry (MS). The reaction sequence was carried out in a one-pot reaction using a multicatalyst. All reaction steps were thoroughly analyzed by electrospray ionization (ESI) MS (and MS/MS), as well as high-resolution MS for structure elucidation. These studies allow us to shed light on the individual mode of action of each catalytic moiety. Thus, we find that under the epoxidation conditions, the catalytically active N-methyl imidazole for the terminal acylation step is partially deactivated through oxidation. This observation helps to explain the lower efficiency of the catalyst in the last step compared to the monoacylation performed separately. All reactive intermediates and products of the reaction sequence, as well as of the side-reactions, were monitored, and we present a working mechanism of the reaction.
authors.affiliation: Max-Planck Institut für Kohlenforschung, Kaiser Wilhelm Platz 1, 45470 Mülheim an der Ruhr (Germany), Fax: (+49) 208-306-2982.
authors.forename: M Wasim
authors.initials: MW
authors.lastname: Alachraf
authors.affiliation: Institute of Organic Chemistry, Justus-Liebig University Giessen, Heinrich-Buff-Ring 17, 35392 Giessen (Germany).
authors.forename: Raffael C
authors.initials: RC
authors.lastname: Wende
authors.affiliation: Institute of Organic Chemistry, Justus-Liebig University Giessen, Heinrich-Buff-Ring 17, 35392 Giessen (Germany).
authors.forename: Sören M M
authors.initials: SM
authors.lastname: Schuler
authors.affiliation: Institute of Organic Chemistry, Justus-Liebig University Giessen, Heinrich-Buff-Ring 17, 35392 Giessen (Germany).
authors.forename: Peter R
authors.initials: PR
authors.lastname: Schreiner
authors.affiliation: Max-Planck Institut für Kohlenforschung, Kaiser Wilhelm Platz 1, 45470 Mülheim an der Ruhr (Germany), Fax: (+49) 208-306-2982. wschrader@mpi-muelheim.mpg.de.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schrader
keywords: electrospray ionization; mass spectrometry; organocatalysis; reaction mechanisms; structure elucidation