Ein symmetrisches Tetrasulfolenoporphyrin als Reaktivbaustein, Vorläufige Mitteilung

A Symmetrical Tetrasulfolenoporphyrin as Reactive Building Block The efficient preparation of the symmetric tetrasulfolenoporphyrin 1 is reported, which shows good solubility in a variety of solvents. In 1, four sulfone groups that symmetrically bridge the eight methylene groups in β-position at the pyrrole rings provide four sulfolene (=2,5-dihydrothiophene 1,1-dioxide) units which are prone to cleavage by thermally induced extrusion of sulfur dioxide. The tetrasulfolenoporphyrin, accordingly, is indicated to lend itself to specific and multiple refunctionalization by the replacement of the sulfone groups by other functionalities in SO2 extrusion/cycloaddition sequences. The predicted reactivity and the potential of a zinc complex of the tetrasulfolenoporphyrin as a reactive porphyrin module (see 5 b) is tested in exploratory experiments. To this end, thermolysis of the tetrasulfolenoporphyrinatozinc 5 b in dichlorobenzene solution (at 140°) and in the presence of [5,6]fullerene-C60-Ih gives the (fullereno-porphyrinato)zinc 6 still having three sulfolene units and a `diagonal' (difullerenoporphyrinato)zinc 7 that still has two sulfolene units, in 14 and in 43% yield, respectively.