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@PHDTHESIS{Meiners:1009812,
      author       = {Meiners, Yannick},
      othercontributors = {Klankermayer, Jürgen and Leitner, Walter},
      title        = {{D}evelopment of homogeneous catalytic systems for the
                      synthesis of urea derivatives and their application in
                      phosgene-free isocyanate production},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2025-03687},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2025},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University; Dissertation, RWTH Aachen University, 2025},
      abstract     = {In the present thesis, homogenously catalyzed systems based
                      on ruthenium were developed for the conversion of formamide
                      towards urea as well as the utilization of formanilides in
                      strategies for a phosgene-free isocyanate synthesis. The
                      first chapter provides a general introduction in the
                      development and state of the art of Ru(triphos)-based
                      complexes. Moreover, the reactivity of these complexes is
                      discussed and possible ligand modifications are presented.
                      Chapter 2 gives a general overview about the industrial
                      synthesis of urea and the literature on alternative
                      procedures. In the following, the catalytic synthesis of
                      urea from formamide and ammonia is investigated focusing on
                      strategies for catalyst recycling and evaluation of involved
                      catalyst species. Moreover, efforts are made for improving
                      catalyst performance leading to [Ru(triphos)(OC6(CF3)2H3)2]
                      as most promising catalyst. Furthermore, this complex shows
                      activity at lower temperatures and a slightly higher initial
                      activity compared to the established [Ru(triphos)(tmm)]
                      catalyst. In chapter 3, a short overview of transition metal
                      isocyanate complexes is followed by mechanistic
                      investigations of [Ru(triphos)(NCO)2(NH3)]. The formation of
                      the isocyanate ligands is resolved using labeling
                      experiments and the reactivity of this complex with various
                      reagents is evaluated. Exploiting the detected reactivity of
                      Ru-carbonyl complexes with formamide, one of the first
                      examples for a straightforward reactivation strategy for
                      catalytically inactive [Ru(triphos)(CO)2(H)]NTf2 is
                      established. Two separate strategies for a phosgene-free
                      isocyanate synthesis starting from formanilides are
                      demonstrated in Chapter 4. First, the conventional
                      isocyanate synthesis and its implications due to the
                      utilization of phosgene along with the state of art of
                      phosgene-free procedures are introduced. The first
                      phosgene-free pathway presented in this work starting with
                      the challenging selective, catalytic synthesis of
                      N-phenylurea is investigated. Thus, the first known
                      procedure for the dehydrogenative coupling of ammonia
                      towards monosubstituted urea derivatives is realized. The
                      following investigations focus on the conversion of
                      N-phenylurea towards carbamates as isocyanate precursor
                      molecules. After optimization of the reaction conditions for
                      both steps, the reactivity is transferred to industrially
                      relevant diisocyanate precursors. First reactions show the
                      feasibility of this concept towards toluene diisocyanate and
                      methylene diphenyl diisocyanate in principle. In the second
                      part of chapter 4, the second strategy for a phosgene-free
                      alternative to synthesize isocyanates is envisioned. The
                      first step of this novel concept consists of the
                      dehydrogenative coupling of formanilides and secondary
                      amines to trisubstituted urea derivatives. Among several
                      tested ruthenium-based catalysts,
                      [Ru(triphos)(OC6(CF3)2H3)2] shows superior reactivity.
                      Optimization of the reaction conditions was followed by
                      identification of the reaction scope and successful scale-up
                      of the reaction. The synthesized
                      N-phenyl-N’,N’-diethylurea is subsequently applied in
                      decomposition reaction successfully leading to the selective
                      formation of aromatic isocyanates. Performing both steps
                      consecutively demonstrates the general viability of this
                      pathway while the successful transfer to commercially useful
                      isocyanates highlights the industrial relevance of this
                      work.},
      cin          = {154310 / 150000},
      ddc          = {540},
      cid          = {$I:(DE-82)154310_20190725$ / $I:(DE-82)150000_20140620$},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2025-03687},
      url          = {https://publications.rwth-aachen.de/record/1009812},
}