New avenues in C‒C and C‒N bond formation via high energy intermediates

Two topics are addressed in this thesis: Photoredox catalyzed C‒C bond formation and transition metal catalyzed C‒N bond formation via metallonitrenoid intermediates. Both topics are briefly introduced in the Introduction.
In Chapter 1 a new cationic iridium-based photosensitizer was developed containing two chromenopyridinone (Chp) ligands and one di-tert-butylbipyridine (dtbbpy) ligand. The difference of the HOMO-LUMO gap between [Ir(Chp)₂(dtbbpy)]⁺ and the frequently used [Ir(ppy)₂(dtbbpy)]⁺ was measured as a shorter luminescence wave length for the former. The excited state of [Ir(Chp)₂(dtbbpy)]⁺, with a lifetime of 0.5 µs, was studied by pump–probe X-ray absorption near edge structure (XANES) spectroscopy and DFT calculations. In Chapter 2 we describe our efforts to use photoredox catalysis to activate monochloroacetic acid for organic synthesis applications. Under excitation by blue light, the neutral photoredox catalyst fac-[Ir(ppy)₃] could reduce the C‒Cl bond to generate a carboxymethanide radical under mild reaction conditions to form γ-phenyl-γ-butyrolactone and 4-chloro-4-phenylbutanoic acid.
Chapter 3 provides an overview of the development of dioxazolones as efficient nitrene transfer reagents in catalysis since 2012. In Chapters 4 and 5, we demonstrate our efforts to develop a new synthetic method to convert dioxazolones in a selective C‒N bond forming reaction leading to formation of N-acyl amidines. In Chapter 4, we report a new copper catalyzed 3-component reaction for the formation of N-acyl amidines with terminal alkynes, dioxazolones and secondary amines. To get more insights into the new 3-component reaction, we performed the mechanistic study described in Chapter 5.