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Issue 22, 2013
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Formation, structure, and reactivity of meso-tetraaryl-chlorolactones, -porpholactams, and -chlorolactams, porphyrin and chlorin analogues incorporating oxazolone or imidazolone moieties

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Abstract

Reaction of known meso-tetraarylporpholactone free bases 3, made from the corresponding porphyrins, with hydrazine produces three products: It converts the lactone functional group into an N-aminolactam moiety, generating porphyrin-like N-aminoporpholactams 8. It also reduces regioselectively the β,β′-double bond of the pyrrolic moiety opposite to the imidazolone in both the starting material and the N-aminoporpholactam, thus forming the chlorin-like chlorolactones 7 and N-aminochlorolactams 9. An equivalent set of reaction products is also derived from the reaction of porpholactones 3 with tosylhydrazide. Reductive N–N cleavage of the N-aminoporpholactams 8 generated the parent porpholactams 10. The molecular structures of all key compounds were shown by single crystal X-ray diffraction to be essentially planar. Porpholactam 10a can be converted in two steps (enolization and halogenation α to the imine, followed by reductive removal of the halogen) to known imidazoloporphyrin 5a, thus constituting the third independent pathway to replace a β-carbon of a tetraphenylporphyrin by a nitrogen. All these transformations show the flexibility of our ‘porphyrin breaking and mending’ strategy toward the synthesis of novel porphyrin and chlorin analogues incorporating non-pyrrolic heterocycles that carry functionalities at their periphery.

Graphical abstract: Formation, structure, and reactivity of meso-tetraaryl-chlorolactones, -porpholactams, and -chlorolactams, porphyrin and chlorin analogues incorporating oxazolone or imidazolone moieties

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Publication details

The article was received on 22 Jan 2013, accepted on 12 Mar 2013 and first published on 12 Mar 2013


Article type: Paper
DOI: 10.1039/C3OB40138C
Citation: Org. Biomol. Chem., 2013,11, 3616-3628
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    Formation, structure, and reactivity of meso-tetraaryl-chlorolactones, -porpholactams, and -chlorolactams, porphyrin and chlorin analogues incorporating oxazolone or imidazolone moieties

    J. Akhigbe, J. Haskoor, J. A. Krause, M. Zeller and C. Brückner, Org. Biomol. Chem., 2013, 11, 3616
    DOI: 10.1039/C3OB40138C

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