Document Type
Article
Publication Date
2024
Publication Title
The Journal of Organic Chemistry
Keywords
Aromatic Compounds, Hydrocarbons, Mixtures, Molecular Structure, Pyrroles
Abstract
Acenaphtho-, phenanthro-, and pyrenopyrrole esters, readily available from Barton-Zard reactions of ethyl isocyanoacetate with nitroarenes, were reacted with methyl iodide and KOH in DMSO to give N-methylpyrroles and subsequent cleavage of the ester moieties was accomplished with KOH in ethylene glycol at 200 °C. Condensation with two equiv of an acetoxymethylpyrrole in refluxing acetic acid-2-propanol afforded a series of annulated tripyrranes. Cleavage of the terminal tert-butyl ester groups with trifluoroacetic acid, followed by condensation with a diformylpyrrole and oxidation with FeCl3, gave N-methyl acenaphtho-, phenanthro-, and pyrenoporphyrins. The N-methyl substituent effectively freezes the tautomeric equilibria to maximize interactions between the porphyrin nucleus and the fused aromatic substructures. Analysis of the proton NMR spectra provides evidence of the presence of extended aromatic circuits within these structures. Anisotropy of induced ring current (AICD) plots clearly shows the presence of 30π electron pathways in phenanthro- and pyrenoporphyrins that run around the exterior of the benzenoid fragments. These results demonstrate that N-alkylation can be used to relocate aromatic pathways in porphyrinoid systems.
Funding Source
This work was supported by the National Science Foundation under grants CHE-1855240 and CHE-2247214. The NSF is also acknowledged for providing funding for the departmental NMR spectrometers (CHE-0722385) and mass spectrometer (CHE-1337497) under the Major Research Instrumentation (MRI) program. This article was published Open Access thanks to a transformative agreement between Milner Library and ACS Publications.
DOI
10.1021/acs.joc.4c01760
Recommended Citation
Assessment of Conjugation Pathways in N-Methylporphyrins that Are Fused to Acenaphthylene, Phenanthrene, or Pyrene: Evidence for the Presence of Alternative Aromatic Circuits Jared S. Salrin, Brian G. Carpenter, Deyaa I. AbuSalim, and Timothy D. Lash The Journal of Organic Chemistry Article ASAP DOI: 10.1021/acs.joc.4c01760
Comments
First published in The Journal of Organic Chemistry: https://doi.org/10.1021/acs.joc.4c01760