Accessing functionalised Bicyclo[1.1.1]pentanes via underutilised and novel synthetic pathways for hydrogen gas odorants and broader chemical applications

The need for a non-toxic, distinct and economical hydrogen odorant that does not interfere with the catalyst of a fuel cell is critical for widespread adoption of hydrogen-based technologies. Bicyclo[1.1.1]pentanes (BCPs) have garnered significant attention in recent decades for their potential pharmaceutical applications. Due to their unique structure, a specifically functionalised BCP has the capability to also be employed as an odorant. This thesis explores routes to access functionalised BCPs primarily through the use of 1,3-diiodobicyclo[1.1.1]pentane (DIBCP), the iodine adduct of [1.1.1]propellane, chosen for its superior storability and underutilised nature. The nucleophilic reaction between DIBCP and the sulfide, tetrahydrothiophene, was optimised and extended to various pyridines, sulfides, tertiary amines, and quinolines. Pyridinium salts were found to be the most reactive, especially those with electron-donating substituents at the meta or para positions, resulting in high yields. The synthetic utility of several pyridinium compounds was subsequently demonstrated through a variety of chemical transformations. Additionally, DIBCP was shown to act as a Lewis acid catalyst, enabling condensation reactions between indoles and acetone that were not achievable with traditional methods. Compared to previous studies, the scope of iodo-BCP salts has been significantly expanded, and a deeper mechanistic understanding of their formation has been achieved. Detailed structural and safety analyses were also conducted using X-ray crystallography and DSC/TGA techniques. Ultimately, this work provides high-yielding synthetic routes to BCP-quinolinones and pyridinones, with significant potential for future applications in medicinal chemistry. Although the hydrogen odorant objective was not fully realised, a solid framework for future exploration has been established.