Maßgeschneiderte Ruthenium-Katalysatoren für die stoffliche Nutzung von CO2 in Kombination mit molekularem Wasserstoff
- Tailor-made ruthenium catalysts for the material use of CO2 in combination with molecular hydrogen
Thenert, Katharina Maria; Klankermayer, Jürgen (Thesis advisor); Leitner, Walter (Thesis advisor)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen University, 2018
This doctoral thesis deals with the ruthenium-catalyzed utilization of CO2 in combination with molecular hydrogen. In the first part of this work, the N-methylation of different nitrogen-containing compounds using the ruthenium complex [Ru(triphos)(tmm)] as a catalyst and CO2 and hydrogen for the construction of the methyl groups was investigated. Under optimized reaction conditions, the N-methylation of ammonia, ammonium chloride and nitrobenzenes was successful. In addition, the influence of different substituents in the multicomponent coupling of aldehyde, amine and CO2 was studied. The second part of this work deals with the acid-catalyzed alkylation of amines for the synthesis of phenylpyrrolidines from aromatic amines and cyclic ethers. HNTf2 and Al(OTf)3 were identified as catalysts for this reaction. Under optimized reaction conditions high yields of the corresponding phenylpyrrolidine were obtained starting from primary amines. In addition, an alkyl group transfer was observed using secondary amines and cyclic ethers as substrates. In the third part of this thesis, a novel catalytic synthesis was developed for the preparation of dimethoxymethane (DMM) from methanol, CO2 and hydrogen. The developed reaction pathway provides the first direct reductive access to DMM. A ruthenium triphos complex in combination with a Lewis and/or Brønsted acid as a co-catalyst was identified as a suitable multifunctional catalyst system for the complex reaction sequence. Under optimized reaction conditions a TON of 513 was achieved for DMM. In addition, the developed reaction protocol was successfully used for the synthesis of different dialkoxymethanes from CO2, H2 and the corresponding alcohol. Regarding the reaction pathway, methyl formate and methoxymethanol were identified as intermediates and the construction of the methylene group from CO2 and H2 was clarified by a 13C labeling experiment. Based on these results, the reaction was further investigated using formic acid as a C1 synthon. Under optimized reaction conditions, the TON for DMM could be increased to 1076 starting from formic acid.