Synthesis of new representatives of A3B-type carboranylporphyrins based on meso-tetra(pentafluorophenyl)porphyrin transformations

Abstract

A carboranylporphyrin of A3B-type bearing a single pentafluorophenyl ring was prepared through the regioselective nucleophilic aromatic substitution reaction of the p-fluorine atoms in 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin with 9-mercapto-m-carborane. The reaction of this porphyrin with sodium azide led to the selective substitution of the p-fluorine atom in the pentafluorophenyl substituent with an azide functionality which upon reduction with SnCl2 resulted in the formation of the corresponding porphyrin with an amino group. Pentafluorophenyl-substituted A3B-porphyrins were studied and transformed to thiol and amino-substituted compounds allowing for the preparation of porphyrins with different reactive groups such as hydroxy and amino derivatives capable for further functionalization and conjugation of these porphyrins to other substrates. In addition, conjugates containing maleimide or biotin entities in the structure of carborane A3B-porphyrin were also synthesized based on the amino-substituted A3B-porphyrin. The structures of the prepared carboranylporphyrins were determined by UV–vis, IR, 1H, 19F, 11B NMR spectroscopic data and MALDI mass spectrometry.

Keywords

• bioconjugation
• carboranes
• fluorine
• porphyrin
• snar aromatic substitution