Efficient cascade reactions for luminescent pyrylium biolabels catalysed by light rare-earth elements.

Cascade catalysis allows multiple chemical steps to occur in a well-defined sequential manner without the isolation of reaction intermediates, and has been applied for the efficient preparation of natural products, pharmaceuticals and agrochemicals, with the preparation of organic functional dyes having been rarely explored. In the present study, light rare-earth elements are found to catalyse cascade reactions from simple aromatic substrates and acetic anhydride to give luminescent pyrylium salts with yields up to 50% under mild conditions. The cascade reactions have been coupled to supramolecular assembly to form aqueous pyrylium nanoparticles that can function as protein labels. [ABSTRACT FROM AUTHOR]