Catalysis, continued cycloaddition

Heterocyclic compounds are indispensable in recent far-reaching developments in the material and biological sciences because they can be used as a substructure in functional materials, agrochemicals, and pharmaceuticals. Transition-metal catalysis continues to be a fruitful source of new methods for the synthesis of heterocyclic compounds, since transition-metal catalysts can be used to construct complex structures directly from easily accessible starting materials under neutral and mild reaction conditions. The cycloaddition of unsaturated molecules is one of the most straightforward and atom-economical reactions for constructing substituted heterocyclic compounds [20]. 

Very recently, as a consequence of their continuing interest in combining metal/ organic catalysis, Han et al. expanded the chemistry combining chiral phosphoric acid and gold catalysis. By incorporating an Au complex-catalyzed Danishefsky diene formation and chiral phosphoric acid-promoted enantioselective [4h-2] cycloaddition into the tandem reaction [69], they obtained pentacyclic frameworks in high yields and selectivities (Scheme 9.66). 

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