Gram-scale synthesis of porphycenes through acid-catalyzed oxidative macrocyclizations of E/Z-mixed 5,6-diaryldipyrroethenes

Abstract

A set of novel porphycenes was synthesized on a gram-scale in high overall yields by optimization of macrocyclization of E/Z-mixed 5,6-diaryldipyrroethenes.

Symmetry Reduction of Porphycenes with Finely Tuned Optical and Electronic Properties through Oxidative Cyclization of E/Z‐Mixed Dipyrroethenes

“…Compounds 1, 2, 4,a nd 5 were synthesized according to previous reports. [10] Compound 3 was prepared in two steps. First, the Friedel-Crafts acylation of 3,5-dimethoxylbenzoyl chloride and pyrrole in the presence of AlCl 3 afforded 2-(3,5-dimethoxy)benzoyl pyrrole (3a)i n5 4% yield.…”

“…Alternative aryl substituents to those in 1 were explored to realize the easy separation and optoelectrical tuning of unsymmetric porphycenes. We also attempted to obtain an unsymmetric porphycene by using two different dipyrroethenes 2 and 3.W hen using similar procedures to the synthesis of 8,p orphycene 9 was easily separated in ap ure form by silica gel column chromatography in 8.6 %y ield from 18 and 17,w hich were obtained in 20 %a nd 24 %y ields (R f = 0.90 (17), 0.25 (9), and 0.10 (18)w ith CH 2 Cl 2 /n-hexane = 1:1), respectively.F urthermore, by using other different dipyrroethenes 3 and 4 as precursors, 10 was easily separated in a yield of 19 %f rom 18 and 19,w hichw ere obtained in 15 % and 40 %y ield (R f = 0.90 (19), 0.50 (10), and 0.20 18w ith CH 2 Cl 2 /n-hexane = 3:1), respectively.T he introduction of an electron-rich group (-OMe) allowed easy separation of the unsymmetric porphycenesinapure form from the corresponding symmetric porphycenes. In contrast, unsymmetric porphycene 11 was not obtainedw hen 4 and 5 were used as precursors, probablyo wing to their different reactivities, with only symmetric porphycene 19 produced.…”

“…E/Z-mixed dipyrroethenes were used because E/Z-isomerization under acidic conditions has been observed in situ. [10] Although porphycene synthesis by using oxidative coupling reactions was first reported in 2008, only symmetric porphycenesh ave been produced to date. [10,11] To our knowledge,t his is the first report of unsymmetric porphycene synthesis using a" pre-modification" route, as shown in Figure 1c.T his study provides important information for tuning the properties of porphycene derivatives in materials science, biochemistry,and nanotechnology.…”

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

“…[180] As ac onsequence of their high electron density,p yrrolebased compounds are often cumbersome substrates for reactions involving strong oxidants and acids. [181] However, the efficient intramolecular coupling of pyrrole rings can be achieved under carefully optimized conditions. [182] Ap rominent example was provided in 2007 by Müllen and coworkers,who synthesized the rim-fused hexapyrrolylbenzene 177 (Figure 13).…”

Highly malleable haem-binding site of the haemoprotein HasA permits stable accommodation of bulky tetraphenylporphycenes

“…1b) for incorporation into HasA, as the gram-scale synthesis of 9,10,19,20-tetraphenylporphycenes (Ph 4 Pc) has been reported recently. 19 Despite the alluring photophysical and catalytic properties of metallo-9,10,19,20-tetraphenylporphycenes, they have never been considered as potential targets for incorporation into haemoproteins.…”