Divergent Reactivity in Cu^II-Catalyzed Oxidative Coupling between Indole/Tryptamine Derivatives and β-Arylacrylic Acids

Abstract

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-1<i>H</i>-pyrrolo[1,2-<i>a</i>]indoles. In contrast, upon changing the oxidant to ^<i>t</i>BuOOH and the solvent to DCM, the reaction course switched to the unprecedented oxidative coupling/cyclization cascade to give the tetracyclic pyrrolo[2,3-<i>b</i>]indolines selectively.