Synthesis of meso-pyrrole-substituted 22-oxacorroles by a "3+2" approach

Hemanta Kalita, Dhrubajyoti Kalita, Way-Zen Lee, Jayesh Bellare, Mangalampalli Ravikanth

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Abstract

Unsymmetrical 22-oxacorrole containing two aryl groups and one pyrrole group at the meso position was synthesized by condensing one equivalent of 16-oxatripyrrane with one equivalent of meso aryl dipyromethane under mild acid-catalyzed conditions followed by oxidation with 2,3-dichloro-5,6-dicyano-1, 4-benzoquinone (DDQ). This [3+2] condensation approach was expected to yield meso-free 25-oxasmaragdyrin but unexpectedly afforded unsymmetrical meso-pyrrole-substituted 22-oxacorrole. We demonstrated the versatility of the reaction by synthesizing four new meso-pyrrole-substituted 22-oxacorroles. The reactivity of α-position of meso-pyrrole was tested by carrying out various functionalization reactions such as bromination, formylation, and nitration and obtained the functionalized meso-pyrrole-substituted 22-oxacorroles in decent yields. The X-ray structure obtained for one of the functionalized meso-pyrrole substituted 22-oxacorrole revealed that the macrocycle was nearly planar and the meso-pyrrole was in the perpendicular orientation with respect to the macrocyclic plane. The meso-pyrrole-substituted 22-oxacorroles absorb strongly in 400-700nm region with one strong Soret band and four weak Q bands. The 22-oxacorroles are strongly fluorescent and showed emission maxima at ≈650nm with decent quantum yields and singlet-state lifetimes. The 22-oxacorroles are redox-active and exhibited three irreversible oxidations and one or two reversible reduction(s). A preliminary biological study indicated that meso-pyrrole corroles are biocompatible.

Original languageEnglish
Pages (from-to)10404-10413
Number of pages10
JournalChemistry - A European Journal
Volume20
Issue number33
DOIs
Publication statusPublished - 2014 Aug 11

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Keywords

  • ABC-type corroles
  • UV/Vis spectroscopy
  • biocompatible
  • fluorescent probes
  • pyrrolyl-22-oxacorroles

ASJC Scopus subject areas

  • Chemistry(all)

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