Mathematisch-Naturwissenschaftliche Fakultät

Leibniz-Institut für Katalyse e.V. an der Universität Rostock

Fachgebiet: Optical in situ spectroscopy

The benefit of coupling different in situ spectroscopic methods (ATR-FTIR / UV-vis / Raman spectroscopy) is exemplarily demonstrated by the means of two reactions as application examples: the Lewis acid mediated formal [3+3] cyclocondensation reaction of a diene with a keteneacetale and the heterogeneously catalysed enantioselective hydrogenation of imines. For both reactions new reactors (deep-temperature cell, probe autoclave) have been developed enabling in situ measurements under real reaction conditions

For the [3+3] cyclocondensation reaction it was demonstrated that the nature of the formed product depends on the different intermediates formed between the ketenacetal and the acids (complexation or acid catalysed rearrangement reaction). Furthermore the mechanisms of similar reactions (including other Lewis acids like AlCl₃, Al₂O₃ and TiO₂ or substrates like N-salicylideneaniline) could be successfully elucidated.

The effectiveness of the hydrogenation depends on the specific interaction of the tested ketimines with the phosphoric acid ester used as chiral modifer. This interaction is mainly influenced by the used solvent and leads to the formation of a carbocation (CH₃OH) or a contact ion pair in (CH₂Cl₂, CF₃CH₂OH). Furthermore, the detected strong adsorption of imines and modifier on the Pt/Al₂O₃ catalyst affect their efficiency and acitivity in the reaction.