Peripheral metalation, oxygen-substituted

The preparation of oxygen substituted porphyrazines as analogues to the thiol appended porphyrazines proved to be a formidable challenge. Unlike the sulfur appended porphyrazines for which Na2(mnt) was a readily available precursor, no simple dinitrile precursor could be prepared for the analogous oxygen systems. In 1997, this hurdle was overcome through the preparation of a chiral dispiroketal appended pz (11), which could be further deprotected to form the diol and then either peripherally metalated or converted to the pyridazine (10). These oxygen appended porphyrazines are described in Section VI. 

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