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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]

• A novel and capable magnetically Lewis acid catalyst based on graphene oxide (GO) was introduced for the synthesis of pyrazole and pyranopyrazol derivatives. • The new catalyst was prepared as a heterogeneous Lewis acid composite by immobilization of BF 3 on GO-Fe 3 O 4. • Pyrazole and pyranopyrazol derivatives were synthesized in desirable yield in the presence of new catalyst. • High surface area, chemical and thermal stability, good selectivity, high reactivity with easily magnetically separation are some of advantageous of new catalyst. • Molecular docking studies were performed to predict the interaction mode of the synthesized compounds toward the EGFR kinase as a possible target. The creation of non-toxic acidic catalysts has benefited greatly from the immobilization of acidic materials on solid substrates. In the present work, a novel and capable magnetically Lewis acid catalyst based on graphene oxide (GO) was introduced for the synthesis of pyrazole derivatives. The new catalyst was prepared as a heterogeneous Lewis acid composite by immobilization on BF 3 on GO-Fe 3 O 4. The magnetic and recoverable catalyst was characterized by FT-IR (Fourier‑Transform Infrared Spectroscopy), FESEM (Field Emission Scanning Electron Microscopy), XRD (X‑Ray Diffraction), EDS (Energy-Dispersive X-Ray Spectroscopy), ICP (Inductively Coupled Plasma), VSM (Vibrating Sample Magnetometer) and TGA (Thermogravimetry Analysis) techniques. Catalytic activity of the GO-Fe 3 O 4 –BF n checked out in the synthesis of pyrazole (3a-3f) and 2,4-dihydropyrano[2,3- c ] pyrazole (8a-8f) derivatives under mild conditions. Pyrazole and pyranopyrazol derivatives were synthesized in desirable yield in the presence of our new catalyst. High surface area, chemical and thermal stability, good selectivity, high reactivity with easily magnetically separation are some of advantageous of our catalyst. The catalyst can also be recycled for several times without reducing its catalytic efficiency. Furthermore, molecular docking studies were performed to predict the interaction mode of the synthesized compounds toward the EGFR kinase as a possible target. [Display omitted] [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]