A new series of aza-BODIPYs (CNÀ X) with significantly redshifted absorbances were designed and synthesized by installation of various electron-donating groups on the para-positions of 3,5-phenyl groups while strong electron-withdrawing groups (nitrile groups) were fixed on the para-positions of 1,7-phenyl moieties. Interestingly, strong electron-donating groups such as N'N-dimethylaniline (CNÀ NMe 2) could provide strong NIR absorption up to 857 nm and weak fluorescence emission up to 967 nm, whereas strong evidence supported heat production via non-radiative decay after excitation. Electrochemical studies revealed that the substituents on the dyes showed strong effects on the oxidation potentials where the oxidation wave of CNÀ NMe 2 occurred at the lowest overpotential, followed by CNÀ OMe, CNÀ Me, CNÀ Br and CNÀ H, respectively. Calculations were also performed to understand the push-pull effect of the substituents on the aza-BODIPY systems. Finally, applications of dyes in NIR cancer cell imaging and the NIR-II photothermal effect were also investigated.
5-Substituted-2-ethoxy-1,3,4-oxadiazoles were conveniently prepared through a one-pot sequential N-acylation/dehydrative cyclization between ethyl carbazate and N-acylbenzotriazoles in the presence of PhP-I as a dehydrating agent. Subsequent treatment with a stoichiometric amount of alkyl halides (X = Cl, Br, I) enables a rapid access to a variety of 3,5-disubstituted 1,3,4-oxadiazol-2(3H)-ones in good to excellent yields.
An ultrasound-assisted one-pot acylation/cyclization reaction between N-acylbenzotriazoles and 2-hydroxybenzaldehydes has been developed for the synthesis of substituted 3-arylcoumarins. Using ultrasound not only allows rapid and clean conversion but also simplifies experimental setup and parallel workup leading to rapid generation of 3-arylcoumarin libraries under mild, solvent-free, and chromatography-free conditions.
A facile, efficient, and economic method toward N-acylbenzotriazoles was reported using 2,4,6-trichloro-1,3,5-triazine in combination with triethylamine as a carboxylic acid activator. Through reacting 1H-benzotriazole with the generated triacylated triazine intermediate, a series of N-acylbenzotriazoles could be rapidly prepared in high yields without column chromatography. Graphical abstract
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