The nitroaldol reaction is demonstrated as an efficient dynamic covalent reaction in phosphate buffers at neutral pH. Rapid equilibration was recorded with pyridine‐based aldehydes, and dynamic oligomerization could be achieved, leading to nitroaldol dynamers of up to 17 repeating units. The dynamers were applied in a coherent stimuli‐responsive molecular system in which larger dynamers transiently existed out‐of‐equilibrium in a neutral aqueous system rich in formaldehyde, controlled by nitromethane.
Triazole derivatives constitute an important group of heterocyclic compounds have have been the subject of extensive study in the recent past. These compounds have shown a wide range of biological and pharmacological activities. In this work, new fused tricyclic 1-(3-nitrophenyl)-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1,5]-benzodiazepines have been synthesized by the thermal cyclization of N'-(2,3-dihydro-1H-1,5-benzodiazepin-4-yl)-3-nitrobenzohydrazides. After screening ethanol, toluene and 1-butanol as solvents, butanol-1 was found to be the best choice for the cyclization reaction in order to obtain the highest yields of tricyclic derivatives. The chemical structures of the synthesized compounds were elucidated by the analysis of their IR, 1H- and 13C-NMR spectral data. For tentative rationalization of the reaction processes, the global and local reactivity indices of certain compounds, taking part in the reaction pathway, were assessed by means of quantum mechanical calculations using the conceptual density functional theory (DFT) approach. This work could be useful for the synthesis of new heterocyclic compounds bearing a fused triazole ring.
The nitroaldol reaction is demonstrated as an efficient dynamic covalent reaction in phosphate buffers at neutral pH. Rapid equilibration was recorded with pyridine‐based aldehydes, and dynamic oligomerization could be achieved, leading to nitroaldol dynamers of up to 17 repeating units. The dynamers were applied in a coherent stimuli‐responsive molecular system in which larger dynamers transiently existed out‐of‐equilibrium in a neutral aqueous system rich in formaldehyde, controlled by nitromethane.
Functionalized gold nanostructures with efficient, broadband absorption
properties are of interest for a variety of biomedical applications. In
this study, we report a plasmon-enhanced functionalization methodology
that results in selective surface conjugation of a fluorescent probe <em>via</em>
two-photon excitation under visible-wavelength laser irradiation. The
fluorescent probe was designed to incorporate a thiolated
4-piperidinyl-1,8-naphthalimide (SNaph) entity, carrying a photolabile
6-nitroveratryl (NV) protecting group, straightforwardly synthesized in a
few steps in good yield. Efficient plasmon-enhanced photodeprotection
of the NV-group, followed by thiol-gold bond formation on gold
nanoisland substrates was recorded upon exposure to 650 nm laser light,
supported by confocal laser scanning microscopy (CLSM). Photolysis of
the labile NV-group, thereby efficiently exposing the free mercapto
group of the thiolated 1,8-naphthalimide, was recorded upon
UV-irradiation at 350 nm, whereas no cleavage occurred at 650 nm. No
conjugation occurred on featureless, gold-plated flat substrates under
the same conditions. Surface plasmon-enhanced two-photon excitation at
plasmonic hotspots in the absorber layer thus resulted in selective and
efficient conjugation of the fluorescent probe to the structured
surfaces. The resulting laser-assisted approach introduces the advantage
of accomplishing selective molecular functionalization at plasmonic
hotspots, owing to the combined, simultaneous effects of long-wavelength
deprotection and spontaneous conjugation.
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