A Simple and Efficient One‐Pot Synthesis of Substituted Benzo[b]furans by Sonogashira Coupling–5‐endo‐dig Cyclization Catalyzed by Palladium Nanoparticles in Water Under Ligand‐ and Copper‐Free Aerobic Conditions

Abstract

A simple and efficient procedure for the synthesis of 2-substituted benzo [b]furan derivatives has been developed by the reaction of 2-iodophenols and arylacetylenes in water catalyzed by palladium nanoparticles generated in situ in open air. The reaction does not require any additive, ligand, or co-

Fluorescent 1-Arylidene-1,3-dihydroisobenzofuran: Ligand-Free Palladium Nanoparticles, Catalyzed Domino Synthesis and Photophysical Studies

“…We believe that reaction proceeds through a standard pathway of oxidative addition of 2‐iodobenzylalcohol to PdNPs followed by transmetalation, reductive elimination and cyclization to give desired biaryl product with regeneration of PdNPs for next cycle (Figure ) . A trial reaction has been carried out to check the species responsible for the cyclization step and we observed that both PdNPs and base K 2 CO 3 are essential for cyclization.…”

Sonogashira Reactions Using Nanocatalysts

“…47 This one-pot coupling-cyclization process for the preparation of benzofurans has been performed using as catalyst Pd-NPs generated in water by reduction of Na 2 PdCl 4 with sodium dodecyl sulphate, which also acted as a stabilizer. 48 Thus, benzofurans such as 16 have been obtained after coupling of 2-iodophenols such as 14 with terminal alkynes such as phenylacetylene in the presence of the generated Pd-NPs, and triethylamine in refluxing water at 100 • C, the Sonogashira intermediate 15 being cyclized in situ to give the final heterocycle (Scheme 4.5). The aqueous suspension containing the catalyst after the reaction has been recycled for three runs with gradual loss of efficiency due to agglomeration of the nanoparticles after each cycle.…”

Synthesis of green nanocatalysts and industrially important green reactions

“…The reaction protocol involved the use of ethanol as the solvent, potassium carbonate as the base, and PVP capped palladium nanoparticles as the catalyst, so the protocol is environmentally friendly green reaction. The synthesis of 2-substituted benzo[b]furans was conducted in water and involves the Sonogashira coupling reaction between 2-iodophenols with phenylacetylenes followed by 5-endo-dig cyclization (69). Figure 16 shows an example of a TEM image of palladium nanoparticles used as catalysts for the Sonogashira coupling reaction (69).…”

“…The synthesis of 2-substituted benzo[b]furans was conducted in water and involves the Sonogashira coupling reaction between 2-iodophenols with phenylacetylenes followed by 5-endo-dig cyclization (69). Figure 16 shows an example of a TEM image of palladium nanoparticles used as catalysts for the Sonogashira coupling reaction (69). Palladium nanoparticles are prepared in water and uses 2-hydroxypropyl-a-cyclodextrin (a-HPCD) as both a reductant and stabilizer (65).…”

“…TEM image of palladium nanoparticles used as catalysts for the Sonogashira coupling reaction(69). Reproduced with permission from John Wiley and Son.…”