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Dedicated to Professor Franco Cozzi on the occasion of his 70 th birthday. "Senatores boni viri, senatus mala bestia"The reaction between epoxides and CO 2 to yield cyclic carbonates is efficiently promoted under solvent-free and relatively mild reaction conditions (0.5 mol % catalyst loading, 0.8 MPa, 125°C) by zinc(II) complexes of pyridine containing macrocyclic ligands (PcÀ L pyridinophanes). The zinc complexes have been fully characterized, including X-ray structural determination. The [Zn(II)X(PcÀ L)]X complexes showed good solubility in several polar solvents, including cyclic carbonates. The scope of the reaction under solvent-free conditions has been studied and good to quantitative conversions with excellent selectivities have been obtained, starting from terminal epoxides. When solvent-free conditions were not possible (solid epoxides or low solubility of the catalyst in the oxirane) the use of cyclic carbonates as solvents has been successfully investigated. The remarkable stability of the catalytic system has been demonstrated by a series of consecutive runs.

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Simple ammonium ferrates are competent catalysts for the CO2 coupling with aziridines to yield 5‐substituted 1,3‐oxazolidin‐2‐ones. Good yields with remarkable selectivity are obtained under mild reaction conditions, room temperature, and atmospheric CO2 pressure, especially for non‐hindered N‐alkyl, N‐benzyl and N‐allyl aziridines, without the need of any co‐catalyst. To shed light on the reaction mechanism, an extensive set of theoretical calculations has been carried out. A viable reaction mechanism involving just one ferrate molecule and where the rate determining step is the 1,3‐oxazolidin‐2‐one ring closure has been found, and the corresponding barrier is compatible with the experimental conditions tested in this study.

This article provides an overview (non-comprehensive) on recent developments regarding pyridine-containing 12-membered tetraazamacrocycles with pyclen or Py2N2 backbones and their metal complexes from 2017 to the present. Firstly, the synthesis...