Ionizing Properties of Noncovalent Organocatalysts - A Systematic Study of Hydrogen Bond Donor Catalysis

• Applicant: Dr. Roland Appel
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2011 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 211504158

Small organic molecules with distinct hydrogen bond donor motifs (e.g., guanidinium, urea, and thiourea derivatives) have emerged to an important class of catalysts for (enantioselective) organic transformations. The strong anion binding properties of such noncovalent organocatalysts have successfully been employed for the heterolytic bond cleavage of neutral organic molecules in order to generate reactive cationic intermediates (e.g., N-acyliminium ions, oxocarbenium ions, and benzhydrylium ions) as viable electrophilic substrates for asymmetric synthesis. A detailed mechanistic investigation of this emerging synthetic strategy will be the general objective of a one years postdoctoral stay in the research group of Professor Eric Jacobsen at Harvard University. For that reason, a systematic evaluation of both the ionizing power of different classes of noncovalent organocatalysts as well as the possible spectrum of their substrates will be performed. The use of heterolysis substrates with adjustable electrofugal and nucleofugal properties will provide a well-defined series of reference compounds, which can be used for the systematic investigation of the ionizing properties of different hydrogen bond donor catalysts. Preparative and kinetic studies of these heterolysis reactions will give a detailed picture about the applicability of a certain catalyst for particular ionization reactions and the corresponding spectrum of possible heterolysis substrates. These investigations will provide useful guidelines for the rational planning and systematic exploration of syntheses involving cationic intermediates generated by hydrogen bond donor catalysis.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Eric N. Jacobsen, Ph.D.