The nickel phthalocyanine 4, which is soluble in common organic solvents, has been synthesized from the corresponding tetracyclone monoadduct 1 and acrolein (3). Reaction of 4 with p‐toluenesulfonic acid leads to the modified phthalocyanine monoaldehyde 5. The capability of 5 to undergo a Wittig reaction has been demonstrated with benzyltriphenylphosphonium bromide (6). Furthermore, a dimer 9 has been synthesized by treating 5 with 0.5 equiv. of xylylenebis(triphenylphosphonium bromide) (8). Dimer 9 constitutes a model compound for corresponding PPV polymers containing phthalocyanine subunits.
The octasubstituted (phthalocyanine)nickel complexes 4a,b, soluble in common organic solvents, bearing four dienophilic functionalities were synthesized from the corresponding phthalodinitriles 3a,b and nickel(II) acetate. Reaction of 4a with tetracyclone 5 led to the phthalocyanine–tetracyclone adduct 6 which is a precursor for an intermediate phthalocyanine 7 containing four isobenzofuran moieties. The capability of 7 to react as tetrakis(diene) was demonstrated by its reaction with naphthoquinone. Furthermore, the unsymmetrical phthalocyanines 13 and 16a,b,c containing one dienophilic functionality were synthesized using a statistical approach. Their tetracyclone adducts 17, 18a,b,c can be used for the synthesis of ladder‐type phthalocyanine dimers. The dimer 22 was synthesized from 18c and p‐benzoquinone via the isobenzofuran intermediate 19 and the benzoquinone adduct 21. For dehydration experiments the naphthoquinone monoadduct 23 was synthesized from 18c. Dehydration of 22 and 23 was carried out successfully with p‐toluenesulfonic acid. The Diels–Alder reactions are discussed with respect to the occurring exo/endo ratio.
A general synthesis of unsymmetrically benzo-annulated phthalocyanines is described. The desired functional group is introduced in the macrocycle by Diels-Alder reaction always starting from the phthalocyanine precursor 1. Complete aromatization is accomplished by reacting the Diels-Alder product with a dehydrating agent like p-toluenesulfonic acid or DBU.
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