Convenient Synthesis of Isocyanate and Isothiocyanate-Substituted Boron Dipyrromethene Dyes and Derivatives

Starting from nitro-substituted phenyl rings, the preparation of boron dipyrromethene dyes carrying amino functions was achieved in good yields. Conversion of the p-aminophenyl group to the corresponding isocyanate and isothiocyanate is feasible under mild conditions. Various combinations allow the production of luminescent molecules bearing mono- or disubstituted urea or thiourea substituents. When two adjacent amino functions are present, a simple protocol allows the production of pyridineindole and dipyridophenazine derivatives. The on/off switching of the fluorescence from the nitro to the amino and further to the urea renders these dyes attractive as fluorescent probes.