Efficient Approach to Functionalized β-Imidazolylporphyrins

Abstract

The applicability of the Debus-Radziszewski condensation of 2-formylporphyrins with aromatic -diketones for the straightforward preparation of 2-functionalized porphyrin derivatives by means of the imidazole heterocyclic bridging unit was investigated in details. The successful transformation of the starting materials was observed regardless the meso-substitution pattern of the porphyrin macrocycle. In contrast, the reactivity and stability of the aromatic -diketone is revealed to possess considerable influence onto the reaction path. Thus, the application of phenanthrene-and phenanthrolinedione as well as benzil allowed successful preparation of the expected derivatives, while acenaphthene-quinone, naphthoquinone or 3,5-di-tert-butyl-o-quinone demonstrated low stability under reaction conditions and thus low conversion of the formylporphyrin precursor. The obtained compounds were isolated in pure form and characterized with a set of physicochemical methods. The successful demetalation of the representatives of the synthesized family of derivatives opens further access to a variety of metal complexes.