Solid-Phase Methods for the Synthesis of Cyanine Dyes

We report here a series of studies that explore solid-phase methodologies for the synthesis of various cyanine dyes. The scope of the previously reported catch-and-release method using sulfonyl chloride resin¹ has now been extended to include pentamethine and water-soluble cyanine dyes. We also report a new and chemically distinct synthetic strategy, employing the stepwise attack of heterocyclic carbon nucleophiles on immobilized polyene-chain precursors, allowing the clean synthesis of hydrophobic and hydrophilic trimethine and pentamethine dyes from more easily obtained starting materials. Overall, both approaches appear to be robust and versatile strategies to delivering a wide range of cyanine-based dyes in high purity.