The influence of structured solids (amorphous, lamellar and 3D crystalline) on the regioselectivity of the dibromination of naphthalene using bromine at room temperature has been investigated. The more acidic amorphous catalysts and an acidic clay give rapid reactions and lead to a large preponderance of 1,4-dibromonaphthalene over the 1,5-dibromo compound, while calcined KSF clay, a bentonite material, after a short reaction time gives a small predominance of the 1,5-isomer. Longer reaction times lead to the equilibration of reaction mixtures, which means that the 1,4-isomer eventually predominates in all cases. Based on these observations, it has been possible to devise synthetically useful preparative procedures, involving direct room temperature reactions of bromine with naphthalene, for either 1,4-dibromonaphthalene or 1,5-dibromonaphthalene based on the use of different solids, namely Synclyst 13 and KSF clay, respectively.
The ability to design nanowires (NW) in powder technology provides a great advantage for many applications in a variety of fields ranging from medicine to materials science. In this study, nanoparticles were synthesized simultaneously by using an aqueous two‐phase system, which was an environmentally friendly method since the reducing agent that was not spent in the reaction could be effectively recycled and reused. AgNWs (silver nanowires) with numerous high widths and dyes were easily synthesized between two phases using the 5,8‐dibromo‐2‐(butylamino)naphthalene‐1,4‐dione, a 2‐substituted naphthoquinone. Naphthoquinones are known as reducing agents in the production of metal nanoparticles. Synthesized NWs have an average diameter of 90 nm and an average length of 6 μm. The nanowires produced had a round cross section. Characterization of nanowires and nanoparticles was done with UV‐vis, XRD pattern, SEM, and EDX. As a result of characterization, it showed two relatively sharp absorbances in the UV‐vis spectrum at a wavelength of ~358 and 432 nm. In the XRD analysis, five basic peaks attributed to Ag nanoparticles were observed. When SEM images were analyzed, it was determined that Ag nanowires generally have an average diameter of 90 nm and an average length of 6 μm. Anticancer activity test was performed using the MTT test in the HeLa and HT‐29 cell lines. IC50 value was calculated as 11.54 and 16.07 μg ml, and AgNWs showed anticancer properties at high concentration. Evaluating the influence of AgNWs for the first time, this study has indicated that AgNWs exhibit inhibitory properties on the collagenase enzyme. It was observed that the IC50 rate for the enzyme activity was 346.5 mM (r2: 0.955), and Ki value was 41.09 mM.
An efficient procedure is described for synthesis of 2,5,8-tribromonaphthoquinone (12) from naphthalene in four reaction steps. Silver-promoted solvolysis of hexabromide 3 produces the specific diastereostereoisomer 10. Dehydrobromination of 10 using sodium methoxide gives tribromodihydronaphthalene-1,4-diol 11 in high yield. PCC oxidation of either 10 or 11 results in the formation of 2,5,8-tribromonaphthalene-1,4-dione (12).
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