A Microwave-Assisted Method for the Synthesis of Symmetrical and Unsymmetrical Cyanine Dyes

Cyanine dyes are widely used fluorophores with a range of labeling applications. However, there exists a lack of common, general methods for their synthesis that are applicable to dyes with a broad range of emission wavelengths. Herein, we describe a rapid, microwave-assisted, one-pot procedure for the synthesis of symmetrical trimethine, pentamethine, and heptamethine cyanine dyes in near-quantitative yields. A variation of the procedure allows the moderate-to-high-yielding synthesis of unsymmetrical cyanine dyes bearing -COOH substituents for functionalization.