Advances in organophosphorus chemistry Synthesis, reactivity and recycling

This thesis describes novel methodologies towards the synthesis of organophosphorus compounds, studies on their reactivity and recycling schemes for the regeneration of phosphorus compounds. First, we provide a complete overview of the chemistry of N-heterocyclic carbene (NHC)-phosphinidene adducts (Chapter 1) and demonstrate a possible application of the sterically accessible carbene-phosphinidene adduct ^MeNHC=PPh as phenylphosphinidene transfer agent upon functionalization with ZnCl2 (Chapter 2). This Lewis acid protection enabled the synthesis of the new uncomplexed phosphorus heterocycles upon treatment with the electron-poor heterodienes 9,10-phenanthrenequinone, diphenylketene and trans-chalcone, while ZnCl2 trapped the remaining carbene as an insoluble coordination polymer. In Chapter 3, we show that incorporation of a phosphorus atom to a carbon scaffold can also be achieved with sodium phosphaethynolate (NaOCP), and describe its reactivity with a cyclopropenium cation, which after a number of pericyclic reactions provides access to the phosphorus analogues of tricyclopentanone, cyclopentadienone, and housene. In Chapter 4 we explore the stoichiometric reactivity of frustrated P/B Lewis pairs towards epoxides resulting in epoxide ring-opening and study this reactivity in detail using DFT calculations and kinetic analyses. Finally, Chapter 5 focuses on the mechanistic studies of the Brønsted acid mediated reduction of tertiary phosphine oxides to phosphines. We believe that the development of the efficient method for phosphine oxide recycling is of great importance for the sustainable use of phosphorus in industrial chemistry.