Strain‐Promoted Double Azide Addition to Octadehydrodibenzo[12]annulene Derivatives

Abstract

Octadehydrodibenzo[12]annulenes (DBAs), readily available by the oxidative acetylenic coupling of 1,2‐diethynylbenzene derivatives, were reacted with organic azides. As compared to the well‐known strain‐promoted azide‐alkyne cycloaddition (SpAAC) of 5,6,11,12‐tetradehydrodibenzo[a,e][8]annulene, the reactivity of the DBA alkynes was lower due to the lower strain energy. However, the regioselective double azide addition occurred without any side reactions under mild conditions, yielding bis‐triazole products. The structures of the products were confirmed by an X‐ray crystal structure analysis, and the reaction mechanism was studied by 1H‐NMR spectroscopy and computational studies. It was also found that the DBAs were hardly fluorescent, while the bis‐triazole products showed a green fluorescence with quantum yields up to 5.1 %. Finally, the new strain‐promoted double azide addition to the DBAs was used for step‐growth polymerization, successfully producing a high molecular weight triazole polymer.

π‐Conjugated Macrocycles Bearing Angle‐Strained Alkynes

“…Its symmetrical and planar π‐conjugated structure induced the formation of self‐assemblies, such as nanofibers and gels . As expected from the highly strained structure, the strain‐promoted double azide–alkyne cycloaddition of 77 c takes place regioselectively to give adduct 79 (Figure c) . The electrophilic cyclization of 77 d using an excess amount of iodine under oxygen atmosphere gave two types of diiododiones, 80 a and 80 b .…”

“…[140][141][142][143][144][145] As expected from the highly strained structure,t he strain-promoted double azide-alkyne cycloadditiono f77 c takes place (Figure 31 c). [146] The electrophilic cyclization of 77 d using an excessa mount of iodine under oxygen atmosphere gave two types of diiododiones, 80 a and 80 b. [147] The electrophilic cyclization of 77 b using two equivalents of iodine gave tetraiodide 81,w hichs moothly converted to 80 a' under aerobic conditions.…”

Clicking in harmony: exploring the bio-orthogonal overlap in click chemistry

“…This bis-triazole product emitted green uorescence when irradiated with UV light and therefore could be used in the labelling of azidated molecules, and hence the reaction has the potential to emerge as an important toolbox in material science. 159 Liao and team developed a strategy derived from liver sinusoidal endothelial cells (LSEC) to enhance liver engrament prociency and tagged them with a uorescent probe, indocyanine greenactive in the near-infrared range i.e., from 12500 cm −1 to 4000 cm −1 . LSCE-altered peptides and the uorescent dye were implanted over adipose tissue-derived mesenchymal stem cells via bio-orthogonal click chemistry and metabolic glycoengineering for in vivo tracing and binding boosting the cell therapy.…”

Activated Internal Alkyne‐Based Polymerization†

“…Heating the annulene and 2,7‐diazidofluorene at 85°C in DMF for 2 d furnished the PTA with M w (up to 13800) in high yield (up to 79%). [ 105 ] Taking advantage of the metal‐free feature, this strain‐promoted alkyne‐azide polycycloaddition has been widely used in the synthesis of functional polymers for tissue engineering and therapeutic drug release. [ 106‐109 ]…”