First three-component addition reaction in a series of 1,5-bis(dialkylamino)pentamethinium salts: a simple and efficient approach to tridentate chelating ligand systems

A new approach to tridentate chelating NPN, NPO and OPO ligand systems is described via a tandem reaction of easily available 1,5-bis(dialkylamino)pentamethinium salts (streptocyanine dyes) with diphenylphosphine in the presence of TfOH.