Chemoselective Intramolecular Rauhut-Currier Reaction on a Labile Framework of Enone and Acrylamide: Tricyclohexylphosphine as a Stable and Economical Catalyst

Abstract

Intramolecular Rauhut-Currier (IRC) reaction is an atom-economical way of making carbocyclic and heterocyclic rings. However, its sensitivity towards electronic and steric parameters limits the reaction and stems the need for further development. Acrylamides have been one such left out of their sensitivity. Herein we report an IRC reaction, using acrylamide as a source of initial enolate. The cyclization has been achieved on a labile and challenging framework, prone to decomposition. Different control experiments have addressed the instability of the precursor. Protocol was further extendable to annulation for benzo analogs. We also report tricyclohexylphosphine (PCy3) as a stable, commercial, and easy-to-use nucleophilic catalyst in the field of IRC reactions as compared to earlier well-established trimethyl and tributyl phosphines. Me3P and Bu3P although useful, are sensitive, prone to oxidation, and need careful handling. The protocol leads to the synthesis of piperidone and dihydroquinolone frameworks. A quick study to test the feasibility of catalyzing the Morita-Baylis-Hillman (MBH) reaction by PCy3 was also done successfully, although in moderate yields. © 2024 Wiley-VCH GmbH.