Efficient access to β-vinylporphyrin derivatives via palladium cross coupling of β-bromoporphyrins with N-tosylhydrazones

Abstract

This work describes a new approach to obtain new β-vinylporphyrin derivatives through palladium-catalyzed cross-coupling reaction of 2-bromo-5,10,15,20-tetraphenylporphyrinatozinc(II) with N-tosylhydrazones. This is the first report of the use of such synthetic methodology in porphyrin chemistry allowing the synthesis of new derivatives, containing β-arylvinyl substituents.

Synthesis, Characterization and Photodynamic Activity against Bladder Cancer Cells of Novel Triazole-Porphyrin Derivatives

“…Then, a Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC) reaction with propargylic alcohol, afforded triazoles 4a-f. Oxidation of the hydroxyl group in these intermediates with 2-iodoxybenzoic acid (IBX) in DMSO allowed the isolation of aldehydes 5a-f; the latter compounds, after reaction with the ylide generated from methyltriphenylphosphonium bromide, afforded the desired 4-vinyl-1H-1,2,3-triazoles 1a-f. The Heck coupling reactions between bromo-porphyrin 2 and the 4-vinyl-1,2,3-triazoles 1a-f (2 equivalents) were performed in the presence of Pd(OAc) 2 (20% mol), KOAc (1 equivalent) and Et 4 NBr (1 equivalent) as the catalytic system and using toluene/DMF (2:1) as solvent (Scheme 3) [52]. The 4-vinyl-1,2,3-triazoles were used in slight excess in order to minimize the debromination of porphyrin 2; this is a side reaction well known in palladium-catalyzed cross-coupling reactions involving halogenated porphyrin derivatives [52].…”

“…The Heck coupling reactions between bromo-porphyrin 2 and the 4-vinyl-1,2,3-triazoles 1a-f (2 equivalents) were performed in the presence of Pd(OAc) 2 (20% mol), KOAc (1 equivalent) and Et 4 NBr (1 equivalent) as the catalytic system and using toluene/DMF (2:1) as solvent (Scheme 3) [52]. The 4-vinyl-1,2,3-triazoles were used in slight excess in order to minimize the debromination of porphyrin 2; this is a side reaction well known in palladium-catalyzed cross-coupling reactions involving halogenated porphyrin derivatives [52]. The reactions were maintained under magnetic stirring during 3 h at 120 • C, being confirmed at that time by TLC the total or almost total consumption of the starting porphyrin into a main product.…”