meso,β-Oligohaloporphyrins as Useful Synthetic Intermediates of Diphenylamine-Fused Porphyrin and meso-to-meso β-to-β Doubly Butadiyne-Bridged Diporphyrin^†

The chlorination of β-halo or β,β-dihaloporphyrins with 2-chloro-1,3-bis(methoxycarbonyl)guanidine (Palau′Chlor) proceeded selectively at the neighboring unsubstituted meso position to afford meso,β-dihalo or meso,β,β-trihaloporphyrins. Such oligohaloporphyrins are useful platforms for constructing more-elaborate porphyrin-based extended π systems. For example, meso-chloro-β,β-diiodoporphyrin participated in an efficient single-step synthesis of a diphenylamine-fused porphyrin. In addition, meso-chloro-β-iodoporphyrin was transformed in stepwise fashion into an efficiently conjugated meso-to-meso,β-to-β doubly butadiyne-linked porphyrin dimer, a system which was previously difficult to access without such haloporphyrin precursors.