1,3-Dipolar cycloaddition reaction in porphyrin systems with functionalized alkyl nitrile oxides - synthesis of isoxazoline-fused chlorins

Abstract

Meso-Tetraphenylporphyrin reacts at higher temperature with unstable alkyl nitrile oxides (R-C≡N→O) affording isoxazoline-fused chlorins according to dipolar [3+2]-cycloaddition pathway. The respective nitrile oxides were in situ generated from the corresponding functionalized nitroalkanes in the presence of base (NEt 3, DABCO) and dehydrating agent (PhNCO, (Boc) 2O). Substituent R bearing diverse of functionality allows synthesis of very attractive moieties which may be of potential use as sensitizers in photodynamic therapy. The products obtained are also suitable intermediates for further derivatization of porphyrins. © 2012 The Japan Institute of Heterocyclic Chemistry.