Synthesis and spectral properties of 6′-triazolyl-dihydroxanthene-hemicyanine fused near-infrared dyes

Abstract

<p>Copper(<sc>i</sc>)-catalyzed azide alkyne cycloaddition (CuAAC) to explore the fluorogenic potential of near-infrared (NIR) dihydroxanthene (DHX) triazole dyes.</p>

Deep Red to NIR Emitting Xanthene Hybrids: Xanthene‐Hemicyanine Hybrids and Xanthene‐Coumarin Hybrids

“…In 2020 Gu et al used the click reaction to synthesize series of triazole based HD dyes. [100] The reported hybrids showed λ emi ∼ 745 nm and Stokes shift ∼ 90 nm. In 2021 Ebaston et al synthesized series of NIR emitting (λ emi ∼ 700 nm) O-HD by using iodinated Fisher base.…”

“…Scheme 8 shows the general synthetic route for the synthesis of 6-triazolyl based HD dyes (C-HD) reported by Gu et al in 2020. [100] The synthesis involves copper-catalysed cycloaddition (CuAAC) Click reaction between aliphatic and aromatic azides with a terminal alkynyl-based-dihydroxanthene-hemicyanine (C-HD1) scaffold to obtain (C-HD). (C-HD1) is obtained from (1 r) through Pd catalysed Sonogashira reaction.…”

“…O-HD3, N-HD1, and C-HD1 have different substituent at position 6 of xanthene scaffold. [95,98,100,102] Dimethylamine substituted HD dye is redshifted followed by hydroxy substituent followed by ethynyl substituted HD dyes. [95,98,100,102] It probably due to electron donating nature of dimethylamine that resulted in red-shifted absorption and emission.…”

Chelation-Assisted Interrupted Copper(I)-Catalyzed Azide–Alkyne–Azide Domino Reactions: Synthesis of Fully Substituted 5-Triazenyl-1,2,3-triazoles

“…Copper chelation via N,O and N,S donor sites proved to be much less efficient . The click -reactions of 2-azidosulfonic acid and 4-azidobenzene-1,3-disulfonate afforded the 1,4-disubstituted triazole after more than 3 h of reaction in low yield (Scheme S1).…”

“…The lower effectiveness of the diphenylphosphoryl moiety as the directing group in the synthesis of the triazenyltriazole 10o may be due to large steric hindrance by the Ph 2 P­(O) group, which makes the copper atom of the intermediate copper triazolide less accessible to coordination with a second molecule of (2-azidophenyl)­diphenyl­phosphine oxide. Previous copper­(I)-catalyzed click reactions of 2-azido-sulfonic acids and -sulfonates provided only 1,4-disubstituted triazoles in low yields. The formation of 10p in good yield indicates that the concept of chelation-assisted interception in CuAAC reactions may be extended to a variety of chelating systems.…”