An Approach to Pyrazoline-Fused Chlorins by Dipolar [3 + 2]-Cycloaddition of Iminonitriles to <i>meso</i>-Tetrakis(pentafluorophenyl)porphyrin: Synthesis of New PDT Photosensitizers
作者:Przemysaw Wyrebek、Stanisaw Ostrowski
DOI:10.1246/bcsj.20110408
日期:2012.10.15
meso-Tetrakis(pentafluorophenyl)porphyrin reacts at higher temperature with unstable iminonitriles (R–C≡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).
Abstract Instead of 1,3-dipolar cycloaddition, the nucleophilic addition reaction proceeded smoothly between heterocyclic enamines 1 or 2 and nitrile imine 1,3-dipoles 3 under mild conditions to yield C-hydrazidoyl-substituted heterocyclic enamines 4--6 as the sole product.