Silylethynyl Substituents as Porphyrin Protecting Groups for Solubilization and Selectivity Control

Silylethynyl substituents are proposed as protecting groups for porphyrin derivatives to enhance their solubility and enable regioselective functionalization. After usage as protecting groups, silylethynyl groups at the mesa-positions can be efficiently removed upon heating with aqueous H2SO4 in the presence of a surfactant. This approach was applied to the preparation of unsymmetrically beta-substituted porphyrins and porphin-porphyrin oligomers, which were inaccessible by conventional methods.