Oxidative Coupling of an Enaminoporphyrin: C−C, N−N Linkages or Both?

Abstract

International audienceA symmetrical bis-nickelporphyrin was prepared in very good yield by oxidative coupling of a nickel(II) enaminoporphyrin. This dimer was obtained by the intermolecular reaction of the starting enamine (acting as nucleophile) with the porphyrin radical cation (acting as electrophile) generated in situ. Alternatively, by using different reaction conditions, an N-N linked porphyrin dimer was obtained in moderate yield. The monomeric extended porphyrin leading to the N-N linked dimer was obtained by the intramolecular reaction of the same radical cation with the neighbouring meso-aryl group (acting as nucleophile)

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

“…The porphyrin dimer 322.2 was obtained by Ruppert et al upon subjecting 322.1 to various monoelectronic oxidants, with best results obtained when using 0.55 equiv of [Fe(phen) 3 ] 3+ in the presence of base ( Scheme 322 ). 605 Another porphyrin dimer, 322.4 was obtained in 18% yield upon slow and simultaneous addition of equimolar solution of 322.1 and PIFA to a suspension of sodium carbonate in DCM. Intramolecular cyclization was preferred under these conditions, leading to the formation of an intermediate 322.3 , which subsequently afforded the N–N linked dimeric product 322.4 .…”

“… a Reagents and conditions: (a) Fe­(phen) 3 (PF 6 ) 3 , Na 2 CO 3 , DCM, rt; (b) PIFA, Na 2 CO 3 , DCM, rt. …”