A novel route to 4-chloro-5-alkyl-phthalonitrile and phthalocyanines derived from it

A new route to the synthesis of 4-chloro-5-alkyl-phthalonitrile derivatives was shown by the displacement reaction of 4,5-dichloro-phthalonitrile and diethylmalonate, a CH-acidic precursor, in the presence of K2CO3. Cyclotetramerization of 1-chloro-3,4-dicyano-6-(1,1-dicarbethoxymethyl)benzene and the metal salt without any solvent gave the corresponding metallophthalocyanines (M = Co, Cu or Pd). Transesterification occurred when the reaction was carried out in hexanol in the presence of DBU to obtain the metal-free derivative. Treatment of 1-chloro-3,4-dicyano-6-(1,1-dicarbethoxy-methyl)benzene with sodium ethoxide at ambient temperature and further acidification resulted in 2,9,16,23-tetra(carboxymethyl)-3,10,17,24-tetrachloro-phthalocyaninatopalladium(II) with partial decarboxylation. Its electronic spectrum in aqueous solution indicated no appreciable change over a pH range from 7 to 12. Copyright (c) 2004 Society of Porphyrins & Phthalocyanines.