Porphyrin tetraphenyl-, synthesis

Porphyrin, 5,10,15,20-tetraphenyl-, 4, 386 Porphyrin, vinyl-synthesis, 4, 278, 279 Porphyrin coenzymes in biochemical pathways, 1, 258-260 Porphyrinogen, mcso-tetraaryl-synthesis, 4, 230 Porphyrinogens, 4, 378, 394 pyrazoles, 5, 228 synthesis, 4, 231 Porphyrins, 4, 377-442 acetylation, 4, 395 aromatic ring current, 4, 385 basicity, 4, 400 biosynthesis, reviews, 1, 99... 

The most common methods of attaching substituents to porphyrins utilize ortho-phenyl-substituted derivatives of 5,10,15,20-tetraphenyl-21 H,23//-por-phine (TPP). While (2-aminophenyl) TPP derivatives have been extensively used in the preparation of biomimetic systems,5 the corresponding (2-hy-droxyphenyl) TPP derivatives have only recently been utilized.6 One of the limitations to the use of hydroxy-substituted systems has been the synthesis of 5,10,15,20-tetrakis(2,6-dihydroxyphenyl)-21//,23//-porphine 3. 

The most famous monopyrrole polymerization route to obtain p>orphyrins involves the synthesis of tetraphenyl porphyrins, from reaction between pyrrole and benzaldehyde (Atwood et al., 1996). This procedure was first developed by Rothemund (Rothemund, 1935) and, after modification by Adler, Longo and colleagues (Adler et al., 1967), was finally optimized by Lindsey s group (Lindsey et aL,1987). In the Rothemund and Adler/Longo methodology the crude product contains between 5 and 10% of a byproduct, discovered later to be the meso-tetraphenylchlorin which is converted in the product under oxidative conditions (Fig. 2). 

The structure of N-confused porphyrin (41 in Figure 9.11) was first proposed by Aronoff and Calvin in 1943 when they reexamined Rothemund s synthesis of tetraphenylporphyrin [43]. Because of lack of supporting experimental studies, the concept was under hibernation until the 5,10,15,20-tetraphenyl-substituted 41 was isolated as the byproduct in the Lindsey synthesis of meso-aryl porphyrins, 50 years later [44]. Currently, many more N-confused and X-confused porphyrins have been synthesized and characterized [37,45]. There are indeed innumerable analogs, in addition to the common derivatives of porphyrin, that constitute a huge molecular library. Every individual porphyrinoid has its own characteristic properties. Their aromaticity can be controlled by means of ingenious structural modifications. This encourages researchers to synthesize novel porphyri-noids with tuned properties as required for the destined applications. 

Almost 30 years ago, Whitlock et al. ° developed an efficient diimide reduction method for the synthesis of bacteriochlorins and isobacteriochlorins from porphyrins. Diimide reduction of metal-free tetraphenyl chlorin afforded tetraphenyl bacteriochlorin, while reduction of the corresponding zinc analog produced... 

The mew-substituted porphyrins, though not naturally occurring, are widely preferred candidates in various fields such as biomimetic models, materials chemistry, photodynamic therapy, catalysis, electron transfer, etc. [180]. The synthesis of these derivatives is much simpler compared to their -substituted counterparts. Rothenmund et al. prepared the first mew-tetramethyl porphyrin derivative by the condensation of acetaldehyde and pyrrole [181]. A side-product chlorin , a porphyrin-related macrocycle, which is largely, but not completely aromatic in nature, is usually formed in this reaction. However, chlorins can be easily oxidized to form the corresponding porphyrins. Alder et al. developed a new method in the 1960s to synthesize tetraphenyl derivatives by the condensation reaction of benzaldehyde and pyrrole in the presence of acidic solvents under refluxing... 

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