Hyun-sub Park
Department of Chemistry Hanyang Univ., Seuol, South Korea

Abstract:

In view of recent surge of phase transfer catalysis mediated by chiral N-quat salts, it is highly desirable to have a concise access to structurally diverse ammonium salts. These salts also form an important subclass of ionic liquids that have diverse application areas, for which 'chiral ionic liquid' is especially intriguing. However, a catalytic process of non-substitution type has not been possible in the realm of cross-coupling reaction, presumably due to the enthalpic penalty.

We found that the gold catalyzed addition of tertiary amines onto alkynes is highly dependent on the pKa of the solvent and appropriate balancing the acid-base property of the substrate-solvent led to a concise access to ammonium salts of various types proceeding at rt. We also found that the alpha vinyl proton undergoes a facile H/D exchange under weakly basic condition. Some of the preliminary studies on the derivatization at the alpha-position (to N-atom), will also be discussed. Manipulation of counter-anion of these quaternary ammonium salts is important not only for their purification but also for modulating the physical properties of these salts, such as hydrophobicity, solubility, and viscosity. For this purpose, several strategies of introducing soft and hard counter-anion will be presented.

Keywords: gold catalyst, quaternary ammonium salt, phase transfer catalyst