Thi Thuan Tran: Novel Synthetic Methodologies for Main Group Element Reagents and Substrates

Abstract

Carbon-carbon double bonds in alkenes are highly valuable due to their versatility in chemical transformations and their presence in pharmaceuticals and natural products. As such, discovering new methods for synthesizing compounds containing C=C double bonds has been at the heart of organic chemistry for a long time. In this context, chapter 2 introduces a novel [2+2] cycloaddition reaction between the Si=C double bond of a silene and the C=O bond of aldehydes and ketones as a key reaction for alkene synthesis. The initial product of this non-ionic version of the Peterson olefination is an unusual four-membered 1,2-silaoxetane, which subsequently undergoes retro-cycloaddition to form alkene products.

On the other hand, light-mediated chemistry presents a compelling alternative to traditional radical reactions from a green chemistry perspective, as it operates under mild conditions and exhibits high functional group tolerance. Herein, we applied principles of organic photoredox catalysis for the activation of halophosphines, and the preparation of phosphine derivative. Chapter 3 gives a brief introduction to photochemistry, including visible light-driven photoredox catalysis and photochemical reactions of electron donor acceptor (EDA) complexes. 

In chapter 4 and 5, the development of a new photocatalytic method for the reduction of trivalent phosphorus compounds using an iridium-based photocatalyst is discussed. The developed methodology can be used to prepare complex organophosphorus species, as well as secondary arylphosphines. It is found that product speciation and reaction kinetics are sensitive to the nature of the P-substituent (aliphatic or aromatic), solvent, and nature of the halide and heteroatoms.

In chapter 6, the formation of an EDA complex between N-containing electron donors and halophosphonium salts, and the use of this adduct in a phosphine synthesis is described. This method offers a photochemical approach for transforming phosphine oxides into phosphines, addressing the drawbacks of traditional metal-mediated P=O bond reductions.