This review provides an overview of the catalytic activity of iron complexes of nitrogen ligands in driving carbene transfers towards CC, C–H and X–H bonds. The reactivity of diazo reagents is discussed as well as the proposed reaction mechanisms.

The cost-effective TPPH 2 /TBACl-catalyzed (TPPH 2 = dianion of tetraphenyl porphyrin; TBACl = tetrabutyl ammonium chloride) carbon dioxide cycloaddition to N-aryl aziridines was successful in synthesizing N-aryl oxazolidin-2-ones. A catalytic tandem reaction was also developed, in which N-aryl aziridines were initially synthesized and then reacted with carbon dioxide without being purified.The procedure occurred with a very high atom economy, molecular nitrogen being the only by-product of the entire tandem process. In addition, the mechanism of catalytic cycle was investigated by DFT calculations.

Molecules containing an aziridine functional group are a versatile class of organic synthons due to the presence of a strained three member, which can be easily involved in ring-opening reactions and the aziridine functionality often show interesting pharmaceutical and/or biological behaviours. For these reasons, the scientific community is constantl y interested in developing efficient procedures to introduce an aziridine moiety into organic skeletons and the one-pot reaction of an alkene double bond with a nitrene [NR] source is a powerful synthetic strategy.Herein we describe the catalytic activity of iron or ruthenium complexes in promoting the reaction stated above by stressing the potential and limits of each synthetic protocol.

The reaction between N-substituted-2-arylaziridines and CO 2 is efficiently promoted by ruthenium(VI) imidoporphyrin complexes and yields a mixture of 5-aryl (A) and 4-aryl (B) substituted oxazolidin-2-ones with a regioisomeric A/B ratio up to 99:1. Several oxazolidin-2-one molecules were synthe- [a]

In view of the relevance of cyclopropanes and aziridines as synthetic building blocks as well as active parts in biological and pharmaceutical compounds, the development of sustainable synthetic procedures for obtaining these products continues to be a significant challenge. Herein, we report the synthesis of iron and ruthenium glycoporphyrins and their catalytic activity in promoting cyclopropanations and aziridinations by using diazo compounds and aryl azides as carbene and nitrene precursors, respectively. The number and location of [a] Scheme 2. Synthesis of mono and tetra glycoporphyrins 2 and 3.Scheme 3. Synthesis of C 2 -symmetrical porphyrin 7.in Scheme 3. Porphyrin 4 [11] was used as the starting material to take advantage of its pre-organized symmetry, which plays an important role in determining the reaction diastereoselectivity (this aspect will be further discussed in the catalytic section).The reaction of benzyl chloride pickets of porphyrin 4 with NaN 3 forms, in 95 % yield, the corresponding azido derivative 5, which yields Zn(5) in a quantitative yield by reacting with Zn(OAc) 2 2H 2 O. Then, the "click" reaction of Zn(5) with glucos-Eur. J. Inorg. Chem. 2019, 4412-4420 www.eurjic.org

The direct insertion of carbon dioxide (CO2) into three-membered rings, such as epoxides and aziridines, represents a relevant strategy to obtain cyclic carbonates and oxazolidinones, which are two useful classes of fine chemicals. The synthesis of these compounds can be efficiently catalyzed by a combination of metal porphyrin complexes and various co-catalysts in homogeneous systems. The catalytic efficiency of these systems is discussed herein by taking into account both the characteristics of the metals and the nature of the co-catalysts, either when used as two-component systems or when combined in bifunctional catalysts. Moreover, mechanistic proposals of the CO2 cycloaddition processes are reported to provide a rationale of catalytic cycles in order to pave the way for designing more active and efficient catalytic procedures.

The cycloaddition of CO 2 to N-alkyl aziridines was efficiently promoted by the convenient TPPH 2 /TBACl binary catalytic system. The metal-free procedure was effective for the synthesis of differently substituted N-alkyl oxazolidin-2-ones in yields up to 100 % and excellent regioselectivities (up to 99 %). The mechanism of the reaction was proposed based on a DFT study which indicated the formation of an adduct between TPPH 2 and TBACl as the effective catalytic active species.

The protonation of commercially available porphyrin ligands yields a class of bifunctional catalysts able to promote the synthesis of N-alkyl oxazolidinones by CO 2 cycloaddition to corresponding aziridines. The catalytic system does not require the presence of any Lewis base or additive, and shows interesting features both in terms of cost effectiveness and eco-compatibility. The metal-free method-ology is active even with a low catalytic loading of 1 % mol, and the chemical stability of the protonated porphyrin allowed it to be recycled three times without any decrease in performance. In addition, a DFT study was performed in order to suggest how a simple protonated porphyrin can mediate CO 2 cycloaddition to aziridines to yield oxazolidinones.