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Abstract:
Catalytic functional group transfer reactions have emerged as powerful and attractive methods for chemical synthesis. These reactions proceed through a chemical group transfer between a donor molecule and an acceptor molecule, enabling a distinct and powerful strategy for performing chemical reactions. This strategy was recently defined as “shuttle catalysis” by Morandi and co-workers. Shuttle catalysis strategy has two notable features: first, both functionalization (the forward reaction) and defunctionalization (the reverse reaction) can be achieved; second, the use of hazardous reagents can often be avoided. Based on this strategy, a variety of transfer reactions have been developed, such as transfer hydrogenation, transfer hydromagnesiation, transfer hydroformylation, transfer hydroacylation, transfer hydrocyanation, and transfer hydrochlorocarbonylation. Despite these advances, extending the application of shuttle catalysis in other hydrofunctionalization reactions or beyond remains of great interest and significance. This thesis describes the application of shuttle catalysis in several transformations, where the hydrofunctionalization is used for catalyst regeneration and the dehydrofunctionalization is used to transfer a toxic compound, and a hydrofunctionalization reaction.
First, we applied the shuttle catalysis strategy to the Mizoroki-Heck coupling reaction with aryl cyanides, which is otherwise challenging to realize under normal Heck conditions. In contrast to the traditional Mizoroki-Heck coupling reaction where a base is used to enable the regeneration of the metal catalyst, this reaction uses a transfer hydrocyanation step to regenerate the metal catalyst. Using an alkyne as the HCN acceptor, we developed a nickel-catalyzed intramolecular Mizoroki-Heck-type reaction of aryl cyanides (Scheme I a). A palladium-catalyzed intermolecular Mizoroki-Heck-type reaction of aryl cyanides was also developed using an alkene as the HCN acceptor (Scheme I b).
Next, we applied the strategy to the cyanation reaction of aryl (pseudo) halides. In the reaction, shuttle catalysis enables the use of an alkyl nitrile as the cyanating reagent, and the transfer of cyano groups is achieved by a dehydrocyanation process. Under nickel catalysis, we were able to realize this reaction using butyronitrile as a cyanating reagent (Scheme II).
Finally, a hydrochlorination of alkynes was realized through shuttle catalysis. This strategy enables the use of an alkyl chloride as the hydrochlorinating reagent, leading to a broader functional group tolerance compared to previously reported methods using HCl or acid chlorides. In the presence of [IrCl(COD)] as the catalyst, we were able to use 4-chlorobutan-2-one as a HCl source to perform this transformation (Scheme III).
