Synthesis of Di(3-thienyl)benzoporphyrin

Abstract

We have successfully synthesized 2,3-di(3-thienyl)benzo[b]porphyrin based on retro Diels-Alder reaction of bicyclo[2.2.2]octadiene(BCOD)-fused porphyrin and investigated its photoisomerization reaction. 1,2-Diarylethene skeletons are attractive due to the reversible photochemical ring-closure/opening reactions. 1 1,2-Bis(2,5-dimethyl-3-thienyl)ethene derivatives 1 are well-known as a photochromic compound, which could be isomerized into cyclohexadienes 2 under irradiation by UV light with change of the color (Scheme 1). These photochromic diarylethenes have been investigated as photoswitchable luminescent materials 2 and conductive molecular wire. 3 In 2001, two papers on 1,2-di(3-thienyl)perfluorocyclopentene bearing porphyrin were reported as photoswitchable fluorophore and phosphorophore. 4 These photochromic molecules showed reversible photoisomerization between their closed and open forms by irradiation with UV and visible light. In these molecules, dithienylperfluorocyclopentene moiety undergoes photoisomerization reaction, while porphyrin moiety shows photoluminescent property. In closed form, dihydrobenzodithiophene unit is not conjugated to porphyrin ring directly. Herein we report synthesis of 2,3-di(3-thienyl)benzo[b]porphyrin based on retro Diels-Alder reaction of bicyclo[2.2.2]octadiene(BCOD)-fused porphyrin precursor and its photoisomerization reaction. Scheme 1. Photo-induced ring-closure/opening reaction of 1,2-bis(2,5-dimethyl-3-thienyl)ethene

Synthesis of Peripherally Annulated Phenanthroporphyrins

“…Pyrrole 3a was treated with trimethyl orthoformate in trifluoroacetic acid (TFA) to give 4a in 95% yield. Diformyltripyrrane 5 was treated with 3a in the presence of TFA, followed by oxidation with p -chloranil to give a mixture of porphyrin-like products and the desired 6 in 2% yield together with 7 in 5% yield via an inverse-type 3 + 1 procedure . The fused bicyclo[3.2.1]­octene ring of 7 should be formed via the skeletal 1,2-shift rearrangement of the BCOD moiety .…”