Niranjan Panda

Decolourization of Methyl Orange using Fenton-like mesoporous Fe2O3–SiO2 composite

Rapid decolourization of Methyl Orange by Fenton-like mesoporous Fe(2)O(3)-SiO(2) catalyst has been reported. The effect of various parameters such as initial pH, initial H(2)O(2) concentration, Fe content in the catalyst and initial dye concentration on decolourization process were studied. The results show that 20mg of mesoporous Fe(2)O(3)/SiO(2) composite (with Si/Fe=10) was sufficient to decolourize 0.6 mg/ml of Methyl Orange in presence of 2 ml of H(2)O(2) at an initial pH of 2.93 within 20 min. The pH range for effective decolourization (≥90%) was found to be 1-3. Leaching tests indicated that the activity of the catalyst was almost unaffected up to three consecutive cycles although ≤0.2 ppm of Fe ion was leached into treated water in each run.

Synthesis of substituted oxazoles from enamides

Annulation of enamides into 2,5- and 2,4,5-substituted oxazoles by NBS/Me2S in the presence of mild base has been achieved. The reaction conditions are simple and tolerant to a wide variety of substituents including both electron-donating and withdrawing groups to produce oxazoles in one-pot without further purification of the intermediate.

One-pot two-step synthesis of 3-iodo-4-aryloxy coumarins and their Pd/C-catalyzed annulation to coumestans

An efficient protocol for the synthesis of various coumestans from the intramolecular annulation of 3-iodo-4-aryloxy coumarins through C–H activation has been developed. When 3-iodo-4-aryloxy coumarins were treated with 10% Pd/C (0.3 mol% Pd) in the presence of sodium acetate, the corresponding coumestans were produced in good to excellent yield. Reusability of the palladium catalyst was investigated in up to three consecutive cycles and it was found that the yield of the reaction was almost unaltered. Sequential iodination and O-arylation of 4-hydroxy coumarins leading to the 3-iodo-4-aryloxy coumarins were also achieved in a one-pot two-step process starting from aryl iodides in high yield. Pivalic acid was revealed to be the most effective additive for the later method to produce 3-iodo-4-phenoxy coumarins. Different functional groups bearing electron-donating as well as withdrawing groups are also tolerant to the reaction conditions.

Facile synthesis of 3(2 H )-furanones

A practical method for the synthesis of 3(2H)-furanones including the bullatenone was described. Intramolecular cyclization of 4-hydroxyalkynones in the presence of KOH affords the biologically potent furanones in moderate-to-good yield at room temperature. Synthesis of 4-hydroxyalkynones from the reaction of acid chloride and terminal alkyne in the presence of copper iodide at room temperature was also reported.Graphical abstract

A novel carbon quantum dot-based fluorescent nanosensor for selective detection of flumioxazin in real samples

Herein, a carbon quantum dot-based highly selective luminescent probe has been designed for the detection of the pesticide flumioxazin via the alkyne azide click reaction. An azide (N3)-functionalized QD has been synthesized by conjugating 4-azidoaniline on the surface of the CQD by carbodiimide coupling. The turn-on fluorescence of the probe upon the addition of flumioxazin is attributed to the formation of a triazole-functionalized CQD in the presence of Cu(II) and ascorbic acid. The sensing protocol was also successfully validated in a number of compounds containing alkynyl groups. The fluorescence increase factor for flumioxazin (F/F0) works linearly in the concentration range 0–35.4 μg l−1, and the limit of detection is found to be 0.027 μg l−1. The specific recognition of alkynyl groups towards azide in the presence of Cu(II) makes our probe specific and selective towards flumioxazin even in the presence of other pesticides. The utility of the developed sensor has also been explored in real agricultural samples.