HFIP & Brønsted Acid Promoted Direct Distal C‐Alkylation of 2‐Oxindoles and Anilines with Donor‐Acceptor Cyclopropanes

Abstract

Installation of an alkyl chain at a specified position in the aromatic ring via metal-free catalysis is very important. In this regard, we have developed a facile metal-free, extremely selective, user-friendly, environmentally benign and costeffective Friedel-Crafts (FC) alkylation protocol for 2-oxindoles and anilines with donor-acceptor cyclopropanes. Real-time NMR studies reveal that the transformation is governed by the cooperative catalysis of Brønsted acid (TfOH) and HFIP, which facilitates the nucleophilic attack on donor-acceptor cyclopropanes from 2-oxindoles and anilines.

Metal- and additive-free TfOH catalyzed chemoselective O- and S-trifluoroethylation of oxindoles, isoindolines and thio-oxindoles

“…13 Moreover, chemoselective installation of the trifluoroethyl moiety in cyclic amides and thioamides is still unexplored. As a part of our ongoing research on exploring the reactivity of oxindoles and thio-oxindoles, 14 we have unfolded the metal- and additive-free TfOH catalyzed chemoselective trifluoroethylation of oxindoles, isoindolines, and thio-oxindoles (Scheme 1b).…”