A Versatile and Practical One-Pot Strategy for a Greener, Waste-Minimized Synthesis of Aryloxy- and Alkyloxy-Substituted Metallophthalocyanines via Tandem SNAr-cyclotetramerization

Abstract

Phthalocyanines represent molecules of considerable scientific interest, yet their synthesis remains challenging, particularly under environmentally sustainable conditions. Due to the increasingly urgent need for developing sustainable and efficient synthetic methodologies, we report a general, practical, and potentially scalable one-pot procedure for the synthesis of aryloxy- and alkyloxy-substituted metallophthalocyanines. This method integrates a nucleophilic aromatic substitution on the phthalonitrile precursors with a subsequent metal-templated cyclotetramerization, all within a single reaction vessel, thus eliminating the need for intermediate isolation and minimizing solvent and reagents consumption. The protocol is compatible with a wide variety of phenols and alcohols, including sterically hindered or electron-withdrawing substituents, and can be performed using standard laboratory glassware and conventional heating, suggesting its practical suitability for scale-up. Selected phthalocyanines were obtained with up to nearly fourfold higher yields compared to literature-reported two-step procedures (e.g., 27% vs. 7% for tetra(3,5-bis(trifluoromethyl)phenoxy)zinc-phthalocyanine) and were characterized by UV–vis, IR, NMR spectroscopy, and mass spectrometry. Environmental efficiency, assessed through E-factor calculations, achieves over 90% reduction in waste generation relative to literature-reported two-step procedures, demonstrating the advantages of our one-pot strategy in terms of environmental sustainability, operational simplicity together with waste reduction and broader applicability to green phthalocyanine synthesis.