Approach to a Substituted Heptamethine Cyanine Chain by the Ring Opening of Zincke Salts

Abstract

Cyanine dyes play an indispensable and central role in modern fluorescence-based biological techniques.Despite their importance and widespread use, the current synthesis methods of heptamethine chain modification are restricted to coupling reactions and nucleophilic substitution at the meso position in the chain. Herein, we report the direct transformation of Zincke salts to cyanine dyes under mild conditions, accompanied by the incorporation of a substituted pyridine residue into the heptamethine scaffold. This work represents the first general approach that allows the introduction of diverse substituents and different substitution patterns at the C3′−C5′ positions of the chain. High yields, functional tolerance, versatility toward the condensation partners, and scalability make this method a powerful tool for accessing a new generation of cyanine derivatives.

Cyanine Dyes Containing Quinoline Moieties: History, Synthesis, Optical Properties, and Applications

“…, Scheme 16]. The synthesis of symmetrical heptamethine dyes 93 – 97 implies the synthesis of 2 moles of quinolinium salts and 1 mole of the linker, which allows formation of the dye within one step [71–73] . The resulting iodides 94 and 95 may be treated with sodium tetraphenylborate to form new fluorophores 96 and 97 in excellent yields (93–94 %).…”

Cyanine‐Flavonol Hybrids for Near‐Infrared Light‐Activated Delivery of Carbon Monoxide

“…UV/Vis absorption spectra of cyanine‐flavonol hybrids 5 a – b in methanol display an intense absorption band typical for the heptamethine cyanine dyes with λ max =791 and 793 nm, respectively (Figure a and Table ) . The compounds also exhibit emission at λ em =815 and 819 nm, respectively, with the intensity comparable to that of indocyanine green (ICG).…”

“…In addition, such a system exhibits high customization potential for further applications owing to the presence of several versatile structural elements. The N ‐substituents of the indolenine heterocycles can be used to tune its solubility in aqueous media or for bioconjugation of enzyme ligands and antibodies, whereas the C4′ position of the heptamethine chain can be used to tune absorption spectra or photostability, or to attach targeting residues . The phenyl substituent of the flavonol moiety is introduced at a late stage of the synthesis, which allows for the installation of additional substituents.…”

NIR‐Sensitized Activated Photoreaction between Cyanines and Oxime Esters: Free‐Radical Photopolymerization

“…note 6). There were also synthesized many different structural motifs to explain the reactivity at distinct positions in the cyanine …”

“…There were also synthesized many different structural motifs to explain the reactivity at distinct positions in the cyanine. [44] Shown herein for the first time is the NIR-sensitized decomposition of oxime esters,resulting in photoinitiation of radical polymerization. New high-power NIR-LEDs facilitate the decomposition of oxime esters.T he question as to whether decomposition follows an entire photonic mechanism or thermal decomposition might play acertain function as well.…”