Divergent Reactivity in CuII-Catalyzed Oxidative Coupling between Indole/Tryptamine Derivatives and β-Arylacrylic Acids.

Condition-controlled divergent oxidative coupling reactions between indole/tryptamine derivatives and β-arylacrylic acids with the catalysis of copper(II) have been developed. Specifically, a formal Michael addition/dehydration sequence between indoles and β-arylacrylic acids occurred in the presence of catalytic CuBr2 in CH3CN under air, thus affording highly functionalized 2,3-dihydro-1H-pyrrolo[1,2-a]indoles. In contrast, upon changing the oxidant to tBuOOH and the solvent to DCM, the reaction course switched to the unprecedented oxidative coupling/cyclization cascade to give the tetracyclic pyrrolo[2,3-b]indolines selectively.