Photoinduced Proton Transfer in 2-(2′-Hydroxynaphthalenyl)benzoxazole: Observation of Fluorescence with a Small Stokes Shift Induced by Excited-State Intramolecular Proton Transfer
2-(2′-Hydroxynaphthalenyl)benzoxazole (1) emits fluorescence with small Stokes shift from its excited tautomer (K*), produced by excited-state intramolecular proton transfer. Intramolecular hydrogen bonding may be responsible for this phenomenon on comparison with the results of 2-(2′-hydroxyphenyl)benzoxazole (HBO) and 2-(naphthalene-1-yl)benzoxazole (2) as a reference compound.
Highly efficient AgNO<sub>3</sub>
-catalyzed approach to 2-(benzo[<i>d</i>
]azol-2-yl)phenols from salicylaldehydes with 2-aminothiophenol, 2-aminophenol and benzene-1,2-diamine
derivatives in good to excellent yields (63–98%) is described. The reaction proceeds via condensation/intramolecular nucleophilic addition/oxidation process between substituted salicylaldehydes and 2‐aminothiophenol, 2‐aminophenol or benzene‐1,2‐diamine under mild reaction conditions. Notably, this reaction utilizes cheap AgNO3 as a readily available and low‐cost benign oxidant at low catalyst loadings with
描述了一种新的,便捷有效的AgNO 3催化策略,用于制备2-(苯并[ d ] azol-2-基)苯酚衍生物,产率高至优异(63-98%)。反应在温和的反应条件下通过取代的水杨醛与2-氨基硫酚,2-氨基酚或苯1,2-二胺之间的缩合/分子内亲核加成/氧化过程进行。值得注意的是,该反应利用廉价的AgNO 3作为易于获得的低成本良性氧化剂,催化剂负载低,具有出色的官能团耐受性。
Catalyst-free microwave-promoted one pot synthesis of 2-aryl benzoxazoles using MnO2 nanoparticles as a convenient oxidant under mild condition
An efficient and facile protocol for one pot synthesis of a series of 2-aryl benzoxazoles through coupling of o-aminophenol with aromatic aldehydes under microwave irradiation in the presence of MnO2 nanoparticles as oxidant reagent was demonstrated. The MnO2 nanoparticles were prepared via a solid-state chemical reaction technique. The structure of oxidant was assigned by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The target molecules were obtained in good to high yields, high purity and short reaction times. The pure products were identified and characterized by physical and spectral data such as; melting point, IR, 1H NMR and 13C NMR. An efficient and facil protocol for one pot synthesis of a series of 2-aryl benzoxazoles through coupling of o-aminophenol with aromatic aldehydes under microwave irradiation in the precense of MnO2 nanoparticles as oxidant reagent was demonstrated.
MnO2 was found to be an efficientoxidant agent for the synthesis of 2-substituted benzoxazoles through one-pot reaction of o-aminophenol and different aromatic aldehydes in acetonitrile under ultrasonic irradiation. This method was performed under mild conditions with high yields, inexpensive and readily available oxidant agent, facile and easy experimental procedure, simple purification of final products