Modular Construction of Functionalized 2-CF3-Indoles

Org Lett. 2021 Aug 6;23(15):5973-5977. doi: 10.1021/acs.orglett.1c02061. Epub 2021 Jul 12.

Abstract

The reaction of α-CF3-β-(2-nitroaryl)enamines with benzaldehydes led to nitro-substituted α,β-diaryl-CF3-enones in high yield. Subsequent reduction of the nitro-group to the amino moiety by the Pd/C-NH4HCO2 system resulted in intramolecular cyclization to form a 5-membered hemiaminal which is stabilized by the presence of a CF3-group. The reaction of this hemiaminal with various nucleophiles afforded functionalized 2-CF3-indoles isolated in up to quantitative yields. High efficiency and broad synthetic scope of all steps of the sequence were demonstrated. A possible mechanism of the reaction is discussed.