Development and application of bifunctional iminophosphorane organocatalysts

This thesis presents the development and application of bifunctional iminophosphorane (BIMP) organocatalysts, incorporating a triaryl-substituted iminophosphorane organosuperbase for organocatalytic enantioselective reactions. Chapter 2 describes the design and synthesis of a new class of BIMP catalysts and its application in the first organocatalytic enantioselective sulfa-Michael reaction of alkyl thiols to unactivated β-substituted α,β-unsaturated esters. The conjugate adducts were obtained in up to 94% yield and 94% ee. In addition, the reaction was performed on a 1 gram preparative scale with 1 mol% catalyst. Chapter 3 describes the application of BIMP catalysts in the enantioselective desymmetrisation reaction via an intramolecular Michael addition of a pendant pronucleophile to prochiral cyclohexadienone. The high Brønsted basicity of BIMP catalysts was demonstrated in the Michael addition of high pKa pronucleophiles, such as α-substituted malonamate and amide. Chapter 4 describes the application of BIMP catalysts in the challenging Michael addition of malonates to crotonates, cinnamates and methacrylates. For example, the conjugate adduct of malonate and hexafluoroisopropyl cinnamate was achieved in 91% yield and 63% ee in 48 h.