Short‐Chained Anthracene Strapped Porphyrins and their Endoperoxides

• Published in: European journal of organic chemistry Vol. 2020; no. 18; pp. 2735 - 2744
• Main Authors: Callaghan, Susan, Flanagan, Keith J., O'Brien, John E., Senge, Mathias O.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 14-05-2020; John Wiley and Sons Inc
• Subjects: Anthracene; Chloroform; Conformational analysis; Crystallography; Cycloaddition; Endoperoxide; NMR; Nuclear magnetic resonance; Porphyrinoids; Porphyrins; Singlet oxygen; Strapped Porphyrins; White light; Endoperoxide; Porphyrinoids; Strapped Porphyrins; Singlet oxygen; Conformational analysis
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.202000283

The syntheses of short‐chained anthracene‐strapped porphyrins and their Zn(II)complexes are reported. The key synthetic step is a [2+2] condensation between a dipyrromethane and an anthracene bisaldehyde, 2,2'‐((anthracene‐9,10‐diylbis(methylene))bis(oxy))dibenzaldehyde. Following exposure to white light, self‐sensitized singlet oxygen and the anthracene moieties underwent [4+2] cycloaddition reactions to yield the corresponding endoperoxides. 1H NMR studies demonstrate that the endoperoxide readily formed in [D]chloroform and decayed at 85 °C. X‐ray crystallography and absorption spectroscopy were used to confirm macrocyclic distortion in the parent strapped porphyrins and endoperoxides. Additionally, X‐ray crystallography indicated that endoperoxide formation occurred exclusively on the outside face of the anthracene moiety.
Herein, we report the synthesis of three short‐chained anthracene strapped porphyrins and their corresponding endoperoxides, formed by a cycloaddition reaction between in situ generated singlet oxygen and the anthracene moiety. We also synthesized Zn(II)complexes of the strapped porphyrins. X‐ray crystallography and UV/Vis analysis confirmed macrocyclic distortion in the strapped systems.