Synthesis of Porphyrins Di‐ and Tetra‐Functionalized with Nucleobases

Abstract

A library composed of ten porphyrins bearing nucleobases is prepared, following two strategies: substitution or Sonogashira cross-coupling reactions. The former strategy led to the synthesis of four porphyrins (T 2 À Po1, A 2 À Po1, C 2 À Po1 and P 2 À Po1) bearing nucleobases (NBs) at two trans meso-positions. These 4 porphyrins were obtained by reacting 5,15-di(4-(bromomethyl)phenyl)-10,20-dimesitylporphyrin (Po1) with thymine (T), adenine (A), cytosine (C) and 2-amino-6-chloropurine (P), a precursor of guanine (G), respectively in the presence of a suitable base. A fifth porphyrin, 5,15-di(N9-meth-ylphenylguanine)-10,20-dimesitylporphyrin (G 2 À Po1) was obtained by hydrolysis of P 2 À Po1. A thymine tetra-functionalized porphyrin was also synthesized following the same strategy starting from T and 5,10,15,20-tetrakis[4-(bromomethyl)phenyl] porphyrin (Po2). The second strategy based on Sonogashira cross-coupling reactions between 5,15-dibromo-10,20-dipentylporphyrin (Po3) and ethynyl-substituted nucleobases resulted in four rigid porphyrins (U 2 À Po3, C 2 À ZnPo3, A 2 À ZnPo3, and G 2 À ZnPo3).