A Dipyrrin Programmed for Covalent Loading with Fullerenes

We describe here a di-(β,β'-sulfoleno)pyrrin programmed for efficient and specific β,β'-functionalization via [4+2] cycloaddition reactions. At 120 °C and in the presence of an excess of C₆₀ -fullerene the di-(β,β'-sulfoleno)pyrrin decomposed cleanly, furnishing a di-(β,β'-fullereno)pyrrin and the corresponding monofullereno-dipyrrin in an overall yield of 96 %. Hence, relatively mild thermolysis of the di-(β,β'-sulfoleno)pyrrin induced stepwise extrusion of two equivalents of SO₂ , producing highly reactive dipyrrin-β,β'-diene intermediates readily, providing a very effective path to [4+2]-cycloadducts. As presented here by the example of the covalent attachment of C₆₀ -fullerene units, a convenient general methodology for the efficient synthesis of covalent dipyrrin β,β'-cycloadducts is made available.