Modification for Nitration of Halo-substituted meso-Tetraarylporphyrins: A Convenient Scale-up in Small Amount of Solvent

The synthesis of porphyrins with halogens and nitro groups in meso-aryl rings is described. Halo-substituted meso-tetraarylporphyrin derivatives in the reaction with sodium nitrite in trifluoroacetic acid at 40°C (or room temperature) afford 5-(4-nitroaryl)-10,15,20- triarylporphyrins. The above mono-nitro products bearing halogens on meso-aryl rings (F, Cl, Br) are difficult to obtain selectively. The method elaborated herein allows to synthesize them with reasonable yield (of up to 57%), and the reaction can be easily scaled-up. By this route, the preparation of valuable substrates for further transformation to highly substituted ‘synthetic porphyrins’ was presented.