Triflic acid-mediated N-heteroannulation of β-anilino-β-(methylthio)acrylonitriles: a facile synthesis of 4-amino-2-(methylthio)quinolines?

Organic & Biomolecular Chemistry Pub Date: 2021-09-06 DOI: 10.1039/D1OB01151K

Abstract

Various functionalised 4-amino-2-(methylthio)quinolines are synthesised through triflic acid-mediated N-heteroannulation of α-functionalized-β-anilino-β-(methylthio)acrylonitriles for the first time. The N-heteroannulation process is highly chemoselective and has mild reaction conditions. However, this process fails in the absence of the β-methylthio group in the acrylonitriles. In addition, a new double N-heteroannulation process is demonstrated to synthesise indolo[3,2-c]quinolines from non-heterocyclic precursors. Natural product isocryptolepine is synthesised in four steps from an acyclic precursor.

Graphical abstract: Triflic acid-mediated N-heteroannulation of β-anilino-β-(methylthio)acrylonitriles: a facile synthesis of 4-amino-2-(methylthio)quinolines
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