2H-Indazoles are synthesized using copper-catalyzed, one-pot, three-component reactions of 2-bromobenzaldehydes, primary amines, and sodium azide. A copper catalyst plays the key role in the formation of C-N and N-N bonds. This method has a broad substrate scope with a high tolerance for a variety of functional groups.

Benzimidazoles were synthesized by the copper-catalyzed, one-pot, three-component reaction of 2-haloanilines, aldehydes, and NaN(3). The reaction was optimized when 2-iodo- or 2-bromoanilines (1.0 equiv), aldehydes (1.2 equiv), NaN(3) (2.0 equiv), 5 mol% of CuCl, and 5 mol % of TMEDA were reacted in DMSO at 120 °C for 12 h. Good yields resulted, and the reaction showed tolerance toward functional groups such as ester, nitro, and chloro. Aliphatic and heteroaromatic aldehydes also afforded the desired products in moderate to good yields.

In this study, we demonstrated a noble Ag-decorated graphene oxide catalyst (GOSH-Ag) for use in the decarboxylative cycloaddition reaction. The catalyst was easily prepared by depositing Ag nanoparticles on thiolated graphene oxide (GOSH) surfaces. Transmission electron microscopy (TEM) indicated that the nanoparticles were well-dispersed and of a small, approximately 3.7 nm average size. These characteristics resulted in a high surface area, which enhanced the catalytic activity of the supported catalyst. Moreover, it was found that the aggregation of Ag catalysts was inhibited by the strong adhesion between the GOSHs and the Ag nanoparticles during the chemical reactions, thereby permitting their reuse. Indeed, the supported catalyst could easily be separated and recovered from the reaction mixture and reused several times.

Copper‐catalyzed coupling reaction of 2‐iodobenzoic acids and alkynes such as terminal acetylenes, alkynyl carboxylic acids, and trimethylsilylacetylene selectively afforded isocoumarins and phthalides in the presence of cesium carbonate (Cs2CO3) and dimethyl sulfoxide (DMSO). Among the regioselective products, only the 6‐endo‐dig product, isocoumarin, was formed at 100 °C, and the 5‐exo‐dig product, phthalide, was formed as a major product at 25 °C. A variety of alkynes produced the corresponding isocoumarins and phthalides in good yields. A mechanism is suggested in which the formation of 2‐alkynylbenzoic acid as an intermediate via Sonogashira‐type coupling was ruled out in the reaction pathway.magnified image