ABSTRACT
The transmutation of waste into valuable materials has a special place in green chemistry. Herein, we report the preparation of quinazoline-2,4(1H,3H)-diones from 2-iodoaniline, isocyanides, and carbon dioxide in the presence of ZnO NPs stably placed on the surface of dendritic fibrous nanosilica by cellulose (DFNS/cellulose-ZnO) as a catalyst. This is a great economic strategy to create three bonds in a one-pot multicomponent reaction step employing functional groups. To prepare the catalyst, the dendritic fibrous nanosilica surface was first activated using cellulose as a substrate to support ZnO NPs. Cellulose acts as a stabilizing and reducing agent for the ZnO nanocatalyst and eliminates the need for a reducing agent. The structure of the prepared DFNS/cellulose-ZnO was examined by various methods, including thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP). The largest amount of quinazoline-2,4(1H,3H)-diones was obtained under ideal situations in the presence of 5 mg of DFNS/cellulose-ZnO under carbon dioxide (1 atm) utilizing a balloon set at 70 °C for 3 hours. The substance was reused for ten consecutive runs and the quinazoline-2,4(1H,3H)-dione content was more than 92% each time. This indicates the potential for application in the green and economic production of quinazoline-2,4(1H,3H)-diones, especially from low-cost feedstocks.
ABSTRACT
Photocatalytic selective oxidation has attracted considerable attention as an environmentally friendly strategy for organic transformations. Some methods have been reported for the photocatalytic oxidation of sulfides into sulfoxides in recent years. However, the practical application of these processes is undermined by several challenges, such as low selectivity, sluggish reaction rates, requirement of UV-light irradiation, use of additives, and instability of the photocatalyst. Pure monoclinic lead chromate nanoparticles were prepared via a new simple way as Pb and Cr sources. PbCrO4 NPs were synthesized via a green method in the presence of gum of ferula assa-foetida from Pb(NO3)2 and CrCl3 as lead and chromium resources, respectively. The structural analysis of the samples confirmed the formation of PbCrO4 nanostructures in the range of 30 ± 5 nm. The PbCrO4 nanocatalyst was thoroughly characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX) study. Considering the large ionic internal character and high mechanical and thermal stability as well as long-term colloidal stability, this system can be considered as a perfect nanocatalyst by using the host-guest approach. A green and ecofriendly method for oxidation of sulfides to sulfones in the presence of O2 as an oxidant was examined for the synthesised PbCrO4 NPs. The easy and applied reusability of the catalyst was observed after the completion of the reaction under visible-light irradiation.
