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Abstract:
In this thesis, the design and synthesis of highly acidic, flexible imido-(N,N‘-bis(sulfonimidoyl))-diphosphorimidate (I2DPi) catalysts is presented. The introduction of flexibility as design element in organocatalysts is a new concept in asymmetric catalysis and has not yet been applied to highly acidic catalysts. However, it might allow the catalyst to adapt to, and stabilize productive transition states. In our efforts to explore this novel design element, we developed a synthetic route to six enantiopure, electron-poor N-(sulfonyl)-(perfluoro)aryl sulfonimidamides. These point-chiral sulfonimidamides were used in the modular synthesis of imidodiphosphorimidates (IDPis), introducing an element of chirality that is independent of the commonly used BINOL backbone. Thereby enabling the use of more flexible, achiral biphenol-based backbones. The thus obtained three novel I2DPi catalysts were shown to exist as interchanging conformers at 21 °C. Upon application in the unprecedented asymmetric Scriabine-type reaction toward enantiopure intermediates for the synthesis of (–)-(Z)-(β)-santalol, these catalysts outperformed current IDPis in terms of yields and enantioinduction, demonstrating their potential. Future research will focus on exploring the hypothesized “induced-fit” of the catalysts, which is hypothesized to be a consequence of their flexibility. Furthermore, we will explore these catalysts’ generality by modifying the biphenol-based I2DPi catalyst motif and assessing it in challenging transformations in the field.
