Catalytic Asymmetric Chemodivergent C2 Alkylation and [3 + 2]-Cycloaddition of 3‑Methylindoles with Aziridines

Highly
enantioselective C2 alkylation and inverse-electron-demand
[3 + 2]-cycloaddition of 3-methylindoles with 2,2′-diester
aziridine were accomplished. The chemodivergent synthesis provided
an access to two kinds of chiral indole derivatives in good yields
and stereoselectivities in the presence of the chiral N,N′-dioxide/Tm­(OTf)3 or N,N′-dioxide/Ho­(OTf)3 complexes. An eight-coordinated mode of N,N′-dioxide/Tm­(OTf)3 complex was confirmed
by X-ray crystal diffraction to interpret the roles of additives H2O and 1,4-dioxane. In addition, the control experiments indicated
that the substituent of the indole nitrogen atom determined the conversion
patterns in the divergent reactions.