Abstract
A series of indole-fused medium-sized N-heterocyclic systems 10a–h were prepared from laboratory-synthesized indole-based esters 9a–h via intramolecular Friedel–Crafts cyclizations induced by both trifluoromethanesulfonic acid and AlCl3/CH3NO2 catalysts under suitable conditions. The synthetic sequence to precursors 9a–h that started from simple N-methylindole-2-carboxylic acid involved conversion to aminoindoles 2a, b, reaction with α,β-unsaturated acid chlorides to yield acyclic amides 5a–d, ring closure to tricyclic lactams 6a–d, and carbonyl reduction to respective pyrido and azepino tricyclic amines 7a–d, which finally underwent N-alkylations with α- or β-haloesters to produce the required ester precursors. The structures of synthesized compounds without stereochemical implications are established using both spectral and analytical data.
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