title: Regiospecific beta-functionalization of free-base porphyrins by pseudohalogens.
abstract: Pseudohalogens based on iodine ('I-X') can be used to regiospecifically introduce chlorine atoms or acetoxy groups onto the beta-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-alpha-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.
authors.affiliation: Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, UKOX1 3TA.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Matthew N
authors.initials: MN
authors.lastname: Wicks
authors.forename: Paul L
authors.initials: PL
authors.lastname: Burn
mesh_terms: D002712:Chlorides / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D054879:Halogenation; D007455:Iodine / Q000737:chemistry*; D015394:Molecular Structure; D011166:Porphyrins / Q000737:chemistry*; D011810:Quinoxalines / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D002712:Chlorides; D005609:Free Radicals; D011166:Porphyrins; D011810:Quinoxalines; C409084:tetraphenylporphyrin; D007455:Iodine