Synthesis of (2-(Quinolin-2-yl)phenyl)carbamates by a One-Pot Friedel-Crafts Reaction/Oxidative Umpolung Aza-Grob Fragmentation Sequence

J Org Chem. 2022 Jun 17;87(12):7852-7863. doi: 10.1021/acs.joc.2c00502. Epub 2022 May 25.

Abstract

Utilizing the easily available isatin-based propargyl amines prepared from isatins, terminal alkynes, and anilines, (2-(quinolin-2-yl)phenyl)carbamates were prepared by a one-pot reaction in sequence, combining the gold-catalyzed Friedel-Crafts cyclization, oxidative umpolung aza-Grob fragmentation, and nucleophilic addition. In this process, gold-catalyzed cyclization of isatin-based propargyl amines gave 1'H-spiro[indoline-3,2'-quinolin]-2-ones, which were oxidized in situ by hypervalent iodine via the aza-Grob fragmentation to afford isocyano intermediates 2-(2-isocyanatophenyl)quinolines. Followed by the nucleophilic addition with alcohol solvents, (2-(quinolin-2-yl)phenyl)carbamates were synthesized. This procedure features easy operation, a wide substrate scope, and mild conditions.