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Issue 5, 2008
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Regiospecific β-functionalization of free-base porphyrins by pseudohalogens

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Abstract

Pseudohalogens based on iodine (‘I–X’) can be used to regiospecifically introduce chlorine atoms or acetoxy groups onto the β-positions of meso-tetraphenylporphyrins (TPPs). TPPs and a quinoxaline derivative were reacted with iodine monochloride to give mono- or di-chlorinated porphyrins, such that when two chlorine atoms were added they were placed antipodally on the porphyrin ring. Reaction of the porphyrins with a mixture of iodine and silver acetate gave the corresponding mono- and di-acetoxylated porphyrins. The acetoxylated porphyrins could be simply transformed to the corresponding hydroxyporphyrins with subsequent oxidation with the Dess–Martin periodinane, giving a simple new route to chlorin-α-diones and bacteriochlorin-tetraones. From the products of the reactions and a UV–visible spectroscopic study, it is proposed that the reactions proceed via a single electron transfer mechanism through a porphyrin cation radical intermediate.

Graphical abstract: Regiospecific β-functionalization of free-base porphyrins by pseudohalogens

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Publication details

The article was received on 30 Nov 2007, accepted on 19 Dec 2007 and first published on 01 Feb 2008


Article type: Paper
DOI: 10.1039/B718542A
Citation: Org. Biomol. Chem., 2008,6, 879-886
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    Regiospecific β-functionalization of free-base porphyrins by pseudohalogens

    W. Zhang, M. N. Wicks and P. L. Burn, Org. Biomol. Chem., 2008, 6, 879
    DOI: 10.1039/B718542A

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