Synthesis of Mono β‐Pyrrole Substituted Triphyrin(2.1.1)s

Abstract

A series of ten mono β-substituted triphyrin(2.1.1)s were synthesized by coupling mono β-bromo triphyrin(2.1.1) with appropriate boronic acid in THF/toluene/water (1 : 1 : 1) in the presence of a catalytic amount of Pd(PPh 3 ) 4 in 17-67% yields. Different boronic acids such as methyl, phenyl, p-tolyl, p-anisyl, p-fluorophenyl, p-chlorophenyl, 3-thienyl, 3-pyridyl, 4-pyridyl, p-biphenyl boronic acids were used. This synthetic approach to β-substituted triphyrin(2.1.1)s was facile. The mono-β-substituted triphyrin(2.1.1)s were characterized and studied by mass spectrometry, NMR, absorption, electrochemical and DFT/TD-DFT techniques. The spectral studies indicated slight alterations in their electronic properties due to presence of an alkyl/aryl/heteroaryl substituent at the βpyrrole carbon. DFT studies indicated that the pyrrole ring which was substituted with alkyl group at its β-position exhibited more deviation compared to the other two pyrroles of triphyrin(2.1.1) macrocycle from the mean plane. However, the β-aryl/heteroaryl substituted pyrrole showed less deviation from the mean plane and overall β-aryl/heteroaryl macrocycle was planar. Furthermore, the studies also supported the participation of a β-substituent with π-delocalization of triphyrin(2.1.1). TD-DFT studies support the experimental observations.

Synthesis of the β-dipyrrinyl triphyrin(2.1.1) ligand and its coordination complexes

“…14 Compound 2 was treated with p-formyl phenylboronic acid under Suzuki coupling conditions to obtain β-formylphenyl triphyrin(2.1.1) 3 in 60% yield. 15 Compound 3 was reacted with ten equivalents of pyrrole in CH 2 Cl 2 under BF 3 •OEt 2 catalyzed conditions followed by flash silica gel column chromatographic purification to obtain β-dipyrromethanyl triphyrin(2.1.1) 4 as a red solid in 43% yield. 17 The molecular ion peak at 826.3854 in HR-MS and clean 1 H NMR confirmed the identity of compound 4.…”

“…We also successfully synthesized β-bromo triphyrin(2.1.1) 14 2 and used it for the synthesis of different mono-β-aryl substituted triphyrins(2.1.1) such as β-formyl phenyl triphyrin(2.1.1) 3 by reacting it with various aryl boronic acids under Suzuki coupling conditions. 15 In continuation of our work on triphyrins(2.1.1), herein we report the synthesis of β-dipyrrinyl triphyrin(2.1.1) 5 in three simple reaction steps starting with β-bromo triphyrin(2.1.1) and used the dipyrrinyl moiety 16 of triphyrin(2.1.1) as the ligand for the synthesis of novel triphyrin(2.1.1)–metal dipyrrin complexes 6–9 (Chart 1).…”

Synthesis of unsymmetrical 2,3,7,8-tetrabromo meso-5,10,11,16-tetraaryl- triphyrin(2.1.1) and its use in the synthesis of sterically crowded 2,3,5,7,8,10,11,16-octaarylated triphyrin(2.1.1)s

“…However, the chemistry of triphyrin(2.1.1) has been limited until recently due to the inaccessibility of proper synthetic routes. We [15][16][17][18][19][20][21] and others [22][23][24] have developed much simpler, straight-forward synthetic routes for meso-tetraaryl triphyrin(2.1.1) 1 (Chart 1) using readily available precursors. We also developed conditions to introduce bromines regioselectively at the β-pyrrole carbons and successfully synthesized β-monobromo to β-hexabromo triphyrins 2-7 (Chart 1) under simple reaction conditions.…”

Synthesis of triphyrin(2.1.1)-triphyrin(2.1.1) homo dimers and bis-Re(i) triphyrin dimer complex

“…25,26 In addition, we used β-pyrrole brominated triphyrin(2.1.1)s to prepare different β-substituted triphyrin(2.1.1)s such as β-aryl substituted triphyrin(2.1.1)s and triphyrin(2.1.1)-metal dipyrrin conjugates. 27,28 Except for a few of these reports, the chemistry of triphyrin(2.1.1)s is not well developed and there is a huge scope to synthesize these contracted congeners of porphyrins and use them as a substitute in place of porphyrins for various applications. In continuation of our efforts towards developing triphyrin(2.1.1) chemistry, we attempted to prepare the first examples of covalently linked triphyrin(2.1.1) homo dimers by treating 2-bromo triphyrin(2.1.1) with different alkane-diols under Pd(0) coupling conditions.…”