One‐Step Synthesis of 3,4‐Disubstituted 2‐Oxazolidinones by Base‐Catalyzed CO 2 Fixation and Aza‐Michael Addition

2‐Oxazolidinones are saturated heterocyclic compounds, which are highly attractive targets in modern drug design. Herein, we describe a new, single‐step approach to 3,4‐disubstituted 2‐oxazolidinones by aza‐Michael addition using CO 2 as a carbonyl source and 1,1,3,3‐tetramethylguanidine (TMG) as a catalyst. The modular reaction, which occurs between a γ‐brominated Michael acceptor, CO 2 and an arylamine, aliphatic amine or phenylhydrazine, is performed under mild conditions. The regiospecific reaction displays good yields (av. 75 %) and excellent functional‐group compatibility. In addition, late‐stage functionalization of drug and drug‐like molecules is demonstrated. The experimental results suggest a mechanism consisting of several elementary steps: TMG‐assisted carboxylation of aniline; generation of an O ‐alkyl carbamate; and the final ring‐forming step through an intramolecular aza‐Michael addition.