0000000000388950
AUTHOR
Valérie Baveux-chambenoît
Proline-Modified Porphyrin Catalysts for Enantioselective Epoxidations: Design, Synthesis, and Reactivity
International audience; The syntheses of various strapped and −picket-fence× chiral porphyrins are described, and their reactivities towards the enantioselective epoxidation of alkenes are reported. Four L-proline residues provide the chiralityfor the various meso-substituted catalysts, which differ by either the spatial arrangement of the stereogenic centers or the nature and length of the straps. The resulting bridged structures possess four amide linkages ineach strap, leading to highly rigid molecules with well-defined geometries whereas the strapped Fe catalysts gave rise to only moderate enantioselectivities, the C2-symmetrical ones being superior to the D2-symmetrical compounds. The …
Investigation of the Enantioselectivity Observed in Epoxidation Reactions Catalysed by Bis‐Strapped Chiral Porphyrins Derived from L ‐Proline
The enantiomeric excesses obtained during the epoxidation reactions of p-chlorostyrene or 1,2-dihydronaphthalene catalysed by two different series of chiral porphyrins are reported. An attempt is made to correlate the enantioselectivity with the steric hindrance generated by the straps of these catalysts. It is shown that this steric hindrance is influenced by the nature of the strap and that it can be approximated. Additionally, the same strap is tethered in two different fashions on each side of the porphyrin, leading to either D2- or C2-symmetrical catalysts, for which the two sides are identically functionalised.
A Versatile and Convenient Method for the Functionalization of Porphyrins
International audience; The condensation of 3-(chloromethyl)benzoyl chloride with different atropisomers of meso-(tetra-o-aminophenyl)porphyrin (TAPP), followed by the reaction of a series of nucleophilic reagents leads, among others, to precursors of biomimetic models of heme proteins such as cytochrome c oxidase (CcO). This synthesis can also be applied as an efficient two-step reaction to obtain highly functionalized porphyrin derivatives potentially useful for cation binding.
Synthesis and Spectral and Structural Characterization of a New Series of Bis-Strapped Chiral Porphyrins Derived from L-Proline
International audience; New chiral porphyrins were obtained in reasonable yields in three steps, starting from the áâáâ atropisomer of mesotetrakis(o-aminophenyl)porphyrin (TAPP). These potential catalysts for the enantioselective epoxidation of alkenes were obtained by the reaction of different linkers on the same Lprolinoyl-picket porphyrin. Their 1H NMR spectral characteristics, as well as the crystal structure of one of them, clearly indicate that the orientation of the proline cycle depends on the linker used to tether the two pickets on each side of the porphyrin. The same linker is employed for both sides of the porphyrin; hence the resulting D2-symmetric superstructure.
l -Prolinoyl chiral picket iron porphyrins evaluated for the enantioselective epoxidation of alkenes
International audience; Four atropisomers of an L-prolinoyl picket porphyrin were synthesised from tetra-o-aminophenyl porphyrin (TAPP) and were evaluated as alkene epoxidation catalysts after incorporation of iron in the porphyrin core. In the case of the aaaa atropisomer bearing the four amino groups on the same side, a bulky base was employed in order to suppress the eventual reaction on the non-functionalised side of the porphyrin.The resulting enantioselectivities were compared with either other chiral motifs or with the corresponding strapped porphyrins. The enantioselectivities obtained with picket porphyrins are as high as those for strapped porphryins, and in some cases, even highe…
Further synthetic and structural investigations of new pre-organized picket porphyrins
The straightforward synthesis of three new picket porphyrins with a restrained conformation is described. These porphyrins have an unusual behavior due to the conjugated but still flexible nature of their pickets. The crystal structure of their common precusor is also reported and confirms the presumed geometry of this type of picket. Indeed, the latter one is formally obtained by the conjugation of two aromatic rings through an amide bond. Although the specific shape of the picket is expected to overcrowd the center of the porphyrin, it is shown that different types of nucleophilic reagents can add easily on these pickets.