Studies on strain released ring-opening reactions of [1.1.1]propellane

Abstract

[1.1.1]propellane was highlighted as the key precursor of small aliphatic ring derivatives used for bioisosteric replacement in drug candidates. Because of its unique reactivity owing to the central bond with inverted bridgeheads, the ring served bicyclo[1.1.1]pentane (BCP) and exo-methylene cyclobutane by strain-released. This thesis describes ring-opening strategies of [1.1.1]propellane with different types of bond cleavages depending on coupling partners. Chapter 1 introduces the radical-mediated ring-opening of [1.1.1]propellane using the pyridinium salts under the visible light irradiation. The EDA complexation with pyridinium salts and base provides an amidyl radical without photocatalyst. Coupling with [1.1.1] propellane and radicals undergo bicyclo[1.1.1]pentyl amine by the cleavage of the central bond. In Chapter 2, silver(I)-catalyzed carbene transfer reaction of [1.1.1]propellane has been developed to synthesize exo-methylene cyclobutane. The cationic transition metal catalyst diminished the electron density in [1.1.1]propellane, to form the methylene cyclobutyl carbene complex by the complex bond fragmentation.