Bypassing the Inertness of Aziridine/CO₂ Systems to Access 5‐Aryl‐2‐Oxazolidinones: Catalyst‐Free Synthesis Under Ambient Conditions

Abstract

The development of sustainable synthetic routes to access valuable oxazolidinones via CO 2 fixation is an active research area, and the aziridine/carbon dioxide coupling has aroused a considerable interest. This reaction features a high activation barrier and thus requires a catalytic system, and may present some other critical issues. Here, the straightforward gram-scale synthesis of a series of 5-aryl-2-oxazolidinones was developed at ambient temperature and atmospheric CO 2 pressure, in the absence of any catalyst/co-catalyst. The key to this innovative procedure consists in the direct transfer of the pre-formed amine/CO 2 adduct (carbamate) to common aziridine precursors (dimethylsulfonium salts), replacing the classical sequential addition of amine (intermediate isolation of aziridine) and then CO 2. The reaction mechanism was investigated by NMR spectroscopy and DFT calculations applied to model cases.

Ammonium Ferrate‐Catalyzed Cycloaddition of CO2 to Aziridines for the Synthesis of 1,3‐Oxazolidin‐2‐ones

“…The synthesis and characterization of the ammonium ferrates and the employed aziridines, as well as the full characterization of 1,3-oxazolidin-2-ones 2 a-o and piperazines 3 a, 3 a' and 3 k are detailed in the Supporting information. The collected data for 1,3-oxazolidin-2-ones are in accordance with those reported in literature: 2 a, 2 b, 2 h, 2 i and 2 j; [42] 2 c; [57] 2 d and 2 e; [31] 2 f and 2 g; [38] 2 k; [29] 2 l, [53] 2 n, [58] 2 o. [59] General catalytic procedure.…”

Diiron Aminocarbyne Complexes with NCE− Ligands (E = O, S, Se)

“…Motivated by our interest in the chemistry of carbamato species [ 54 , 55 , 56 ] and based on the documented reactivity of isocyanates [ 12 , 57 , 58 ], we tested the reactivity of 2a,c with a range of alcohols and amines, but no reaction occurred even under high-temperature conditions. The substantial inertness of the isocyanate ligand in 2a was observed even towards strong electrophiles (i.e., methyl triflate and trimethylsilyl triflate).…”

Diiron bis‐cyclopentadienyl complexes as transfer hydrogenation catalysts: The key role of the bridging aminocarbyne ligand

“…Due to the presence in solution of a strong base such as KOH, a fraction of isopropanol is assumed to be deprotonated to give the isopropoxide anion. [ 72 ] Isopropoxide is able to interact via hydrogen bond with trans‐3e (reaction complex, RC ; see Figure 4) and then to donate a hydride to the carbyne carbon (isopropoxide to acetone conversion). The related transition state TS1 is accessible under the experimental conditions (ΔH ǂ = 20.6 kcal mol −1 , ΔG ǂ = 28.8 kcal mol −1 ), and the anionic intermediate adduct trans‐3eH /acetone consequently forms ( trans ‐ Int1 , ΔH = −13.5 kcal mol −1 ; Figure 4).…”