Tetrabenzoporphyrins isoindoles

Several syntheses of tetrabenzoporphyrin complexes make use of similar template strategies to those used in phthalocyanine synthesis, so they will be discussed here. An isoindole has been found to undergo a very complex series of reactions promoted by a range of metal ions in refluxing 1,2,4-trichlorobenzene to produce tetrabenzoporphyrin complexes (Scheme 55).240 In contrast, an extremely simple synthesis of tetrabenzoporphyrin can be achieved from 2-acetylbenzoic acid, using zinc as templating metal (equation 44).241... 

Pyrrole is to porphyrin as isoindole is to tetrabenzoporphyrin. The tetrabenzoporphyrins and their tetra-meso-aza derivatives, the phthalo-cyanines, are extended aromatic systems of considerable thermodynamic stability. Because of this, they can sometimes be generated under rather... 

The ideal monomer for the synthesis of a symmetrically substituted tetrabenzoporphyrin by an analogous tetramerization would be expected to be the isoindole 96. This substance has not been prepared, but the expectation of its usefulness is confirmed by the observation that 1,3,4,7-tetra-methylisoindole is an excellent precursor, in spite of the fact that it appears to be structurally unsuitable in that it has one a-methyl group too many. Thus, heating 1,3,4,7-tetramethylisoindole with nickel(II) acetate in 1,2,4-trichlorobenzene under reflux provides the nickel(II) octamethyltetra-benzoporphyrin (97) in 71% yield.123 The transition metal ion has a template effect since without it only a small amount (5%) of the metal-free tetrabenzoporphyrin is formed. Various other metal complexes (Mg, Mn, Fe, Co, Cu) have been made this way.123 124 An alternative route involves fusing the... 

Proton of the methine group connecting the 4 isoindole units in tetrabenzoporphyrine... 

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See also in sourсe #XX -- [ ]

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