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Abstract:
This thesis delineates the development of efficient disulfonimide‐catalyzed enantioselective vinylogous Mukaiyama aldol reactions and their extensions towards double vinlyogous versions. The disulfonimides proved to be very general, tolerating aromatic and aliphatic aldehydes as electrophiles. Focusing on open chain nucleophiles, we investigated differently substituted crotonates and sorbates. The unprecedented double vinylogous Mukaiyama aldol reactions, additions of six carbon atoms to carbonyl compounds, offered a rapid access to eight‐membered ring lactones (ζ‐lactones). Our endeavors towards the improvement of the disulfonimide‐catalysts, led us to the exploitation of cooperative effects. This strategy found its successful embodiment in diarylmethanol‐substituted hydroxy‐disulfonimides, catalysts bearing a tertiary alcohol moiety in the substituents. With these catalysts we were able to efficiently convert very unreactive electrophiles in Mukaiyama aldol processes. Based on mechanistic studies, indicating a Lewis acid mechanism as operative, we presume that hydroxy‐disulfonimides are Brønsted acid assisted Lewis acids. First results with these catalysts allowed for catalyst loadings unprecedented in metal‐free catalysis (as low as 0.0001 mol%).
