A Au nanoparticle-reduced graphene oxide nanocomposite (Au NPs-RGO) was used as an effective and reusable heterogeneous catalyst for the Ullmann homocoupling of aryl iodides with short reaction times and good yields. For the first time, aryl bromides bearing electron-withdrawing groups were coupled in the presence of a catalyst giving moderate yields.Supported Au nanoparticles (Au NPs) and their catalytic applications in heterogeneous organic reactions have attracted considerable attention in recent years. Aldehyde-alkyne-amine coupling (A3-coupling), 1 oxidation of alcohols, 2 secondary amines 3 and carbon monoxide, 4 hydrogenation of olens, 5 Suzuki 6 and Sonogashira 7 reactions, formation of nitrogen containing compounds, 8 etc. are some of the most important applications of supported Au NP catalysts. The catalytic performance of Au NPs-support strongly depends on the size and shape of the Au NPs, the nature of the support, and the Au NPs-support interface interaction. 9 Supporting carriers may function by dispersing and xing the Au NPs. Supports such as oxides (CeO 2 , 10 SiO 2 , 11 Al 2 O 3 , 12 MgO 13 and TiO 2 (ref. 14)), mixed oxides (Mg-Al-O 15 and Ga-Al-O 16 ), polymers (PVP 17 and PS derivatives 18 ) and ordered mesoporous carbon 19 have been used as supports for Au NPs. Among these, it has been reported that the p-interaction of aromatic rings with gold nanoparticles leads to nanoparticle stabilization and improves the catalyst performance in a variety of gold-catalyzed reactions. 9,18,20 Graphene is a two-dimensional sheet of sp 2 bonded carbon atoms, which can be viewed as an extra-large polycyclic aromatic molecule. 21 Recently, graphene has been used as the support for metal and metal oxide that is mainly due to its large surface area, excellent electrical and thermal conductivity, low price, high chemical inertness, ease of modication and strong
A palladium‐catalyzed cascade protocol has been established for the synthesis of 4‐methyl‐1‐(1H‐pyrrolo[2,3‐b]‐quinoxalin‐2‐yl)cyclohexanols and 2‐phenyl‐1‐(1H‐pyrrolo[2,3‐b]quinoxalin‐2‐yl)propan‐1‐ols through the reaction of N‐alkyl(aryl)‐3‐chloroquinoxalin‐2‐amines with calcium carbide and cyclohexanones or 2‐phenylpropanal. This one‐pot process, carried out without any copper salt in the key step of the Sonogashira coupling reaction, provides an efficient method for the synthesis of 2,3‐disubstituted pyrrolo[2,3‐b]quinoxalines in the presence of catalytic amounts of Pd(PPh3)2Cl2 in DMSO/H2O with high yields. The benefit of this strategy is the use of a commercially available, inexpensive, and less hazardous primary chemical feedstock, calcium carbide, as an acetylene source in a wet solvent.
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