Fusion and Desulfurization Reactions of Thiomorpholinochlorins

An unusually nonplanar, ruffled structure that had been suspected for the previously reported [2,3-bismethylenethiomorpholinochlorinato]nickel(II) complex was confirmed by determination of its crystal structure. Treatment of this thiomorpholinochlorin with acid converts the exocyclic double bonds to direct links to the ortho-positions of both adjacent meso-phenyl groups. The crystal structure of this product indicated that the introduction of these linkages did not change the overall conformation of the macrocycle. The reactivity of the bis-linked thiomorpholine moiety with respect to Raney-nickel-induced (hydro)desulfurization reactions was probed, forming a bis-phenyl-linked 2,3-dimethylchlorin, also characterized by X-ray diffraction, and a bis-indene-annulated porphyrin. We also report on the synthesis of the oxygen analogue to the bis-linked thiomorpholine by reaction of a secochlorin bisketone nickel complex with Woollins' reagent. We thus introduce novel methodologies toward the synthesis of porphyrinoids carrying β-to-ortho-phenyl fusions and expand on the scope and limits of the chemistry and interconversion of pyrrole-modified porphyrins.