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.