[3 + 3] Cycloaddition of in Situ Formed Azaoxyallyl Cations with 2-Alkenylindoles: An Approach to Tetrahydro-β-carbolinones.

A novel [3 + 3] cycloaddition between in situ formed azaoxyallyl cations and 2-alkenylindoles has been developed. This concise method allows the efficient construction of a series of tetrahydro-β-carbolinones in good yields under mild conditions. Gram-scale experiments and further derivatization of tetrahydro-β-carbolinones highlighted the potential utility of our method.