Iron and Ruthenium Glycoporphyrins: Active Catalysts for the Synthesis of Cyclopropanes and Aziridines

Abstract

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

Iron catalysts with N-ligands for carbene transfer of diazo reagents

“…For example, the functionalization of the porphyrin core with carbohydrate units enhanced the reaction transdiasteroselectivity, with respect to the unsubstituted porphyrin ligand, and the catalyst solubility in organic solvents. 39 Even if chiral carbohydrate units were present, the reaction was not enantioselective, due to the distance of the catalytically active metal center from the chiral portion of the molecule. The authors envisaged a potential use of glycoporphyrins, to promote cyclopropanation reactions in biphasic media by taking advantage of their amphiphilic nature.…”

Iron: A Worthy Contender in Metal Carbene Chemistry

“…Two final experiments study the addition of either chiral cyclopropane or disaccharide substituents to nonsymmetric porphyrins to obtain new chiral iron catalysts. Despite the increased complexity of the starting porphyrin ligands, the catalysts showed no induction of enantioselectivity and average yields. , …”

“…Despite the increased complexity of the starting porphyrin ligands, the catalysts showed no induction of enantioselectivity and average yields. 73,74 Up to now, the iron-catalyzed cyclopropanation of diazo esters is still limited to electron-rich terminal olefins. An interesting exception was discovered by introducing a ylide group to α,β-unsaturated esters (49), improving electron density on the double bond and thus forming the sought after tri/tetra substituted cyclopropanes (50) (Scheme 8).…”

Azides and Porphyrinoids: Synthetic Approaches and Applications. Part 1—Azides, Porphyrins and Corroles

“…Lay, Gallo and co-workers report the synthesis of iron and ruthenium glycoporphyrins using the CuAAC approach [91]. The new derivatives were used as catalysts in cyclopropanation and aziridination reactions using diazo compounds and aryl azides as carbene and nitrene precursors, respectively (see Section 3.).…”

“…The same group was able to prepare several iron and ruthenium glycoporphyrin complexes P141 (Scheme 47) and reported their uses as catalysts in the aziridination of α-methylstyrene in the presence of several aryl azides. The yields obtained ranged from 10% to 96%, depending on the porphyrin metal complex and also on the substitution pattern at the phenyl ring of the azide [91].…”