An N-linked indole structure was constructed on the 3a-position of pyrroloindoline derivatives via a cascade process involving silver-mediated amination of bromopyrroloindolines with 2-ethynylanilines with subsequent 5- endo-dig cyclization. In this reaction, AgNTf was used as a tandem reagent, which activated the bromo group as a σ-Lewis acid and the alkyne moiety as a π-Lewis acid. Switching from the initial step to the second step was conducted by controlling the temperature. This protocol was applied to the synthesis of various pyrroloindolines, α-carboline, and furoindolines and the total synthesis of a dimeric indole alkaloid, (+)-pestalazine B.
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http://dx.doi.org/10.1021/acs.orglett.9b01399 | DOI Listing |
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