Porphycenes synthesis

The tetrabromo porphycene was used as a starting product for the first synthesis of isocorroles (see Section 1.8.) which are formed from the porphycene by ring contraction on treatment with base. 

Scheme 17 Synthesis of (5-substituted porphycenes and the numbering scheme.

Scheme 18 Synthesis of fi-phenyl-substituted bipyrrole porphycene precursors.

Another improved synthesis of unsubstituted porphycene 38 (R=H) using ferf-butyl substituents as temporary stabilizing groups, as outlined in Scheme 22, has been described (07JPP596). Thus, deprotection of the N-tosyl-protected bipyrrole 46, followed by formylation yields diformyl intermediate 36, which readily undergoes McMurry coupling to produce 38 (R=H, f-Bu). 

Scheme 23 Synthesis of porphycene bearing both alkylic and aromatic substituents.

Scheme 26 Synthesis of an oxidation resistant substituted porphycene precursor.

Scheme 27 Synthesis of asymmetrical raeso-substituted porphycene.

Scheme 28 Synthesis of a porphycene bearing a trifluoromethyl group.

Ar - 4-H2iCj0O-C6H4, 3,4-(H2iCj0)2O-C6H4 Scheme 30 Synthesis of aryl-substituted efio-type porphycenes and its zinc complex. 

Corrphycenes and their metal complexes undergo four distinct one-electron redox steps, two are reduction steps and two are oxidation steps. A comparison with porphyrins and porphycenes indicates that the first reduction potentials of the free base and of metallo-corrphycenes are between those of porphycene 38, the easiest to reduce molecules, and those of porphyrins 2. The oxidation potentials of corrphycenes and porphyrins, however, are quite similar (00IC2850). The synthesis of hemi-porphycene 70 (Scheme 33) has been achieved (05ACI3047) from corrole 8 (R=C6H5). 

Scheme 35 Synthesis of expanded porphycene using vinylogous dialdehyde.

Scheme 38 Synthesis of an extended porphycene containing an sp2 hybridized linked bipyrrole.

Scheme 85 Synthesis of mixed furan-thiophene porphycene.

Scheme 86 Synthesis of a porphycene containing a thiazole ring and nitrogen in its periphery.

Scheme 87 Synthesis of porphycene containing four thiazole units.

Synthesis and characterization of other related macrocycles, including chlorins, " isobacteriochlorins, bacteriochlorins, mono- and dioxoporphyrins, " other more highly saturated hydroporphyrins, N-alkyl- or A-arylporphyrins, some of which are chiral, porphodimethenes, thiaporphyrins, " oxaporphyrins, N-confused " and carbapor-phyrins, porphycenes " and corrphycenes, " tetraazaporphyrins, phthalocyanines, the ring-expanded sapphyrins, texaphyrins and others, and the ring-contracted corroles " and corrolazines have also been synthesized and are discussed in the indicated references. 

Synthesis. The [PFe ] complexes are most conveniently prepared by reduction of the corresponding Fe porphyrins in the absence of potential axial Ugands using either chromium(II) complexes, aqueous dithionite under vacuum, " sodium amalgam, borohydride salts, or zinc amalgam in aprotic organic solvents. Using aqueous sodium dithionite or Zn/Hg an Fe(II) porphycene complex, namely the Fe(II) complex of 2,7,12,17-tetra-n-propylporphycene [(TprPc)Fe ] has also been synthesized by... 

As mentioned earlier, the poor solubility and crystallinity characteristics of the metal complexes derived from porphycene 3.2 inspired the synthesis of a number of P-alkyl-substituted analogs. Not surprisingly, these P-substituted systems showed metal coordination properties similar to those of their unsubstituted counterpart. For instance, the 2,7,12,17-tetrapropylporphycene 3.20 has been shown to form stable complexes with Co(II), Ni(II), Cu(II), Pd(II), and Pt(II) (i.e., 3.63-... 

A reductive McMurry-type approach similar to that used for the synthesis of porphycenes (Chapter 3) and ozaphyrins (Chapter 6) has also been applied to the synthesis of hexapyrrolic macrocycles. This approach has been explored independently by Johnson and Ibers Cava and Merz and Neidlein " and has led to a range of hexaphyrin-(2.0.0.2.0.0)-type expanded porphyrins (e.g. 7.55) that are gen-erically known as homoporphycenes or bronzaphyrins. As is often the case, the trivial name bronzaphyrin, originally coined by Johnson and Ibers ° reflects the color of the macrocycle observed in organic media. Indeed, in solution, these macro-cycles typically exhibit a distinctive bronze color. For the purpose of continuity in this chapter, the name bronzaphyrin will be universally employed for all macrocycles of the hexaphyrin-(2.0.0.2.0.0) type. 

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