Oligomeric cyclization of dinitriles in the synthesis of phthalocyanines and related compounds: the role of the alkoxide anion

Abstract

The formation of phthalocyanine from phthalonitrile has been shown to proceed through reactive precursors condensing to reactive oligomeric intermediates which, as a result of ring-closure reactions, cyclize to conjugated macrocyclic product. The roles of alkoxide anion in the reaction scheme leading to phthalocyanine has been illustrated by isolation of reactive precursor sodium 1-imido-3-methoxyisoindolene and reactive intermediate lithium 1-imido-3-(3-methoxy-5-nitroisoindolenin-1-ylideneamino)-5-nitroisoindole (6) while its role in the overall yield of desired conjugated macrocyclic product has been shown by comparing the yield of magnesium dibenzobarrelenoporphyrazine to that obtained when the alkoxide concentration was reduced during the synthesis.