Synthesis and Diels-Alder Reactions of Some New (Phthalocyanine)nickel Complexes

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 laddertype 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.