An approach to pyrazoline-fused chlorins by dipolar [3 + 2]-cycloaddition of iminonitriles to Meso-Tetrakis(pentafluorophenyl)porphyrin: Synthesis of new PDT photosensitizers

Article abstract of DOI:10.1246/bcsj.20110408

Meso-Tetrakis(pentafluorophenyl)porphyrin reacts at higher temperature with unstable iminonitriles (RC≡N⁺-N^--Ar), affording pyrazoline-fused chlorins, according to dipolar [3 + 2]-cycloaddition pathway. The respective iminonitriles were in situ generated from the corresponding functionalized α-halogenohydrazine derivatives by 1,3-elimination of HX in the presence of base (NEt₃, DABCO). This method allows synthesis of very attractive moieties which may be of potential use as sensitizers in photodynamic therapy (PDT).