Mechanical trapping and in situ derivatization of the porphodimethene intermediate. (June 2022)

• Record Type: Journal Article
• Authors: Tang, M.; Liang, Y.; Liu, J.; Wu, L.; Wang, S.; Bian, L.; Jiang, L.; Tang, Z.-B.; Liu, Z.
• Is Part Of: Materials today chemistry. Volume 24(2022)
• Publication Date: 2022-06
• Subjects: Molecular bows -- Molecular-strain engineering -- Porphyrinogens -- Porphyrins -- Reaction mechanism; Chemistry -- Periodicals; Materials -- Research -- Periodicals; Materials science -- Periodicals; Chemistry; Materials -- Research; Electronic journals; Periodicals; 660.282
• DOI: 10.1016/j.mtchem.2022.100868
• Languages: English
• ISSNs: 2468-5194

Abstract

Abstract: Manipulation of the energy profile of a chemical reaction plays a crucial role in modulating its progress and selectivities. Porphodimethene and phlorin are two key isoelectronic intermediates during the stepwise oxidation process leading to the formation of porphyrin from calix[4]pyrrole. We report here the mechanical capture of porphodimethene instead of phlorin as well as its simultaneous derivatization by means of molecular-strain engineering (MSE). By tuning the linker between its 5- and 15- meso -positions, a constrained porphodimethene has been trapped which can be oxidized with 4, 5-dichloro-3, 6-dioxo-1, 2-benzenedinitrile in the presence of a range of nucleophiles to afford a novel class of stable disubstituted porphodimethene derivatives. Their structures were characterized by NMR spectroscopies, mass spectrometry, and single-crystal X-ray crystallography. Theoretical calculations indicate that the enhanced strain energy resulted from the elongation of the bow-limb in the proposed porphyrin bow favors the formation of the configuration of the porphodimethene intermediate containing two sp 3 -hybridized meso -carbons rather than that of the phlorin consisting of one sp 3 - meso -carbon atom. This work demonstrates that MSE can steer the reaction trajectory through specific intermediates, providing the ability to control precisely the reaction progress and selectivity of desired products. Graphical abstract: Image 1 Highlights: Selective trapping the porphodimethene intermediate without multistep synthesis or harsh reaction conditions. Mechanical trapping of intermediates affords an alternative to conventional adding scavengers for investigating reaction mechanisms. Reaction selectivity can be controlled by steering the reaction trajectory through specific intermediates. In situ oxidation of porphodimethene in the presence of H2 O and alcohols yields a series of novel disubstituted derivatives.