Heterocyclic Aromatic Amide Protecting Groups for Aryl and Phthalocyaninesulfonic Acids

Pyrroles, indole, imidazole, and a pyrazole were treated with 3,4-dibromobenzenesulfonyl chloride to form 3,4-dibromobenzenesulfonamides. The 1-(3,4-dibromophenylsulfonyl)pyrrole and 1-(3,4-dibromophenylsulfonyl)indole were stable to CuCN in DMF to produce 1-(3,4-dicyanophenylsulfonyl)pyrrole and 1-(3,4-dicyanophenylsulfonyl)indole, which upon treatment with ammonia in 2-N,N-dimethylaminoethanol gave the protected phthalocyanine-2,9,16,23- tetrasulfonamides. Base cleavage of these sulfonamides yielded the free acids. A mixed condensation of 4,5-diheptylphthalonitrile and 1-(3,4-dicyanophenylsulfonyl)pyrrole gave 9,10,16,17,23,24-hexakis(1-heptyl)-2-(1- pyrrolylsulfonyl)phthalocyanine. Cleavage of the latter yielded the lithium salt of the monosulfonic acid.