Isomers of β,β-Dinitro-5,10,15,20-tetraphenylporphyrin Derivatives: Valuable Starting Materials for Further Transformations

The synthesis, chromatographic isolation, and structure elucidation of β,β-substituted isomers of dinitro-5,10,15,20-tetraphenylporphyrin complexes are described. meso-Tetraphenyl-porphyrin chelates (Cu(II), Ni(II), Co(II)) upon reaction wit e.g., nitric acid (yellow HNO(3), d = 1.52, diluted to 25–50%) in CHCl(3) formed a mixture of nitro-derivatives with combined yields of ca 80%. This nitration (under optimized conditions: 25–30% HNO(3), 30–40 min, r.t.) can be carried out selectively to give mainly β,β-dinitro-compounds in yields of up to 73%. From the above mixtures of five possible regioisomers that can be formed, usually two or three of them were isolated, for which the structures were assigned on the basis of (1)H NMR spectra including COSY and NOESY measure-ments. These types of products are attractive starting materials for synthesis of potential anticancer PDT agents with unique structures, being practically unavailable by any other alternative method.