From Supramolecular Chemistry to Organocatalysis: .. (XBCBCAT)
From Supramolecular Chemistry to Organocatalysis: Fundamental Studies on the Use of Little-Explored Non-Covalent Interactions in Organic Synthesis
Start date: May 1, 2015,
End date: Apr 30, 2020
Hydrogen-bonds have found widespread use in various fields of chemistry, including supramolecular chemistry, organic chemistry, and more lately organocatalysis. Although a multitude of structurally different hydrogen-bond donors has been developed, their mode of action is in all cases necessarily based on the same interacting atom, hydrogen. In this proposal, we aim to develop first applications for two, previously very little explored non-covalent interactions that are based on electrophilic halogen or chalcogen substituents (“halogen-bonds” and “chalcogen bonds”). The first objective is to open the way for the use of chiral multidentate halogen-bond donors (i.e., halogen-based Lewis acids) for enantiodiscrimination. After the synthesis of suitable candidate compounds, we will apply them in the following research areas: a) the resolution of racemic mixtures by co-crystallization with chiral halogen-bond donors, and b) the use of these Lewis acids in enantioselective organocatalysis. Within the second objective, we will strive to establish first-of-its-kind applications of chalcogen-based Lewis acids in organic synthesis and organocatalysis. In contrast to halogen-bonds, chalcogen-bonds feature two substituents on the interacting atom as well as two electrophilic axes. In the first phase of this aim, we will synthesize neutral and cationic, mono- and bidentate candidate compounds and determine their association constants with a variety of Lewis bases. Based on this date, we subsequently seek to use these novel Lewis acids as activators or catalysts in organic transformations. We anticipate that the realization of these applications, all of which are unprecedented, will be a crucial first step towards establishing further non-covalent interactions as useful tools in chiral recognition and chemical synthesis. In the long-term, we foresee these little-explored interactions becoming powerful complements to the ubiquitous hydrogen-bonds.
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