title: Formation, structure, and reactivity of meso-tetraaryl-chlorolactones, -porpholactams, and -chlorolactams, porphyrin and chlorin analogues incorporating oxazolone or imidazolone moieties.
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.
authors.affiliation: Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Akhigbe
authors.forename: John
authors.initials: J
authors.lastname: Haskoor
authors.forename: Jeanette A
authors.initials: JA
authors.lastname: Krause
authors.forename: Matthias
authors.initials: M
authors.lastname: Zeller
authors.forename: Christian
authors.initials: C
authors.lastname: Brückner