Search

Graphene oxide modified with tryptophan (GO-Trp) has been introduced as a new heterogeneous acid-base biocatalyst for synthesis of some pyran derivatives. GO was prepared according to the Hummer's method and tryptophan as a low-cost green amino acid is covalently bonded to the surface of GO without any organic or toxic reagents in a green way. The new catalyst was characterized by different spectroscopic methods such as Fourier transform infrared, X-ray diffraction (XRD), etc. .... The results of XRD patterns showed an increase in the distance between the GO plates in the presence of the modifying agent which specifies the presence of amino acid between the GO layers. XPS analysis also confirmed successful modification through the presence of C–N bonds in the structure of the catalyst. In addition, improvements in thermal stability and changes in the morphology of the samples were observed using thermogravimetric analysis and Field emission scanning electron microscopy analysis respectively. Evaluation of the catalyst performance in the synthesis of some benzo[b]pyran and pyrano[3,2-c] chromene derivatives showed presentable results. Seven benzo[b]pyran (4a–4g) and five pyrano[3,2-c] chromene (4h–4l) derivatives were synthesized. GO-Trp as a safe, natural and efficient catalyst, could be reused up to 5 runs for synthesis of pyran derivatives without any significant decrease in its potency. High purity of the products and desirable yields are other points that make the present work more attractive. [ABSTRACT FROM AUTHOR]

In this study, a new heterogeneous catalyst was synthesized based on graphene oxide (GO) as a natural material. On the surface of nanosheet graphene oxide, 2-Morpholinoethanamine was immobilized using a non-toxic, green, and simple method. This resulted in the preparation of a bifunctional acid–base nanocatalyst. The synthesized composite was fully characterized using various methods, including Fourier transform infrared spectrometry (FT-IR), scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), mapping, Raman spectroscopy, X-ray diffractometry (XRD), thermogravimetric analysis (TGA), and CHN elemental analysis. The catalytic reactivity of GO-mor was investigated in the one-pot synthesis of some benzo[b]pyran, pyrano[3,2-c]chromene, and polyhydroquinoline derivatives, yielding good efficiency and short reaction times. In addition, several recent studies have shown that some derivatives of pyran, chromene, and quinoline have remarkable anti COVID activity. Particularly, COVID-19 3CLpro/Mpro is considered a potential target for the treatment of this virus. For this purpose, docking models were constructed using the corresponding crystal structures with the synthesized derivatives. Based on the docking score and similarity of the binding mode to remdesivir and elvitegravir (the only approved drugs for the treatment of COVID-19), A2, B1, and C4 were selected as promising candidates for further research. [ABSTRACT FROM AUTHOR]

Graphene Oxide (GO) containing 1‐(2‐aminoethyl) piperazine as a reusable, highly efficient and heterogeneous organocatalyst was prepared using a simple and green way. Epoxide groups on the surface of GO layers were replaced with 1‐(2‐aminoethyl) piperazine by an easy and green technique in a mild condition. The prepared catalyst (GO‐A.P.) was characterized using diverse microscopic and spectroscopic techniques. The presence of organic functional groups on the surface of GO‐A.P. was confirmed by Fourier transform infrared and Raman spectroscopy. X‐ray diffraction analysis showed an increase in the catalyst's interlayer spaces which confirm the successful presence of 1‐(2‐aminoethyl) piperazine molecules on the GO surface. Also interaction between the organic molecules and GO was established by thermogravimetric analysis via weight loss steps. Then, the capability of this catalyst was evaluated in a three‐component coupling reaction for one‐pot synthesis of 12‐aryl‐8,9,10,12‐tetrahydrobenzo[a]xanthen‐11‐one (A1–A7) and also 2‐amino‐4H‐pyrans (B1–B8) derivatives. The target products were obtained in high isolated yields. Furthermore, our catalyst was reusable at least for 5 runs with no significant decrease in its activity. [ABSTRACT FROM AUTHOR]

• GO-Arg was introduced as a new biocatalyst for synthesis of chromen derivatives. • GO-Arg was synthesized in two steps. • The new catalyst was analyzed using microscopic and spectroscopic techniques. • Using of the GO-Arg in the synthesis of chromen derivatives showed respectable results. • Reusing the catalyst up to 5 runs, and getting a very pure product are the other points. L-arginine modified graphene oxide (GO-Arg) was introduced as a new heterogeneous biocatalyst for synthesis of benzo[ b ]pyran and pyrano[3,2‑ c ]chromene derivatives. First GO was synthesized and then, Arg was covalently bonded on its surface. The new catalyst was analyzed using spectroscopic techniques such as Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Energy-dispersive X-ray spectroscopy (EDS) and Raman. XRD analysis results showed that, Arg was located between the graphene oxide layers. Comparison of the bond intensity ratio of the D and G (ID/IG) in GO and GO-Arg confirmed the presence of Arg via covalent bond on the GO surface. XPS analysis also confirmed the successful modification through the presence of C N bonds in the structure. Moreover, changes in morphology of the samples were observed using SEM analyze, respectively. Evaluation of the performance of the catalyst in the synthesis of benzo[ b ]pyran and pyrano[3,2‑ c ]chromene derivatives showed presentable results. Using of amino acid as an available organocatalyst, its stabilization by a simple method on graphene oxide, reusing the catalyst up to 5 times, and introducing a highly pure product are positive points of this work. [Display omitted] [ABSTRACT FROM AUTHOR]