Synthesis of 2-Substituted Benzofurans from o-Iodophenols and Terminal Alkynes with a Recyclable Palladium Catalyst Supported on Nano-sized Carbon Balls under Copper- and Ligand-Free Conditions

Abstract

We have developed a one-step synthesis of benzofurans from o-iodophenol and various terminal alkynes, by using Pd catalyst supported on nano-sized carbon balls (NCB) under copper-and ligand free conditions. This recyclable catalyst could be reused more than 5 times in the same heteroannulation reaction. The results have demonstrated that diverse 2-substituted benzofurans with tolerant functional groups can be prepared simply and conveniently under these conditions.

One-Pot Tandem Hiyama Alkynylation/Cyclizations by Palladium(II) Acyclic Diaminocarbene (ADC) Complexes Yielding Biologically Relevant Benzofuran Scaffolds

“…Important is the comparison of the yields of the aryl benzofuran products obtained in our Hiyama alkynylation/cyclization reaction to those obtained by other methods. In particular, 2-phenylbenzofuran was obtained in 57% at 2 mol % of catalyst 4 loading under our Hiyama alkynylation/cyclization condition which is lower than the near-quantitative yield of 93% obtained using Et 2 Zn (5 mol %), of 90% obtained using a Cu I 2 (pip) 2 complex (1%), and of 88% obtained using Pd­(OAc) 2 -NCB (5 mol %), all obtained using tandem Sonogashira/cyclization reaction between 2-iodophenol and phenylacetylene substrates. The 2-phenylbezofuran synthesis has also been reported in 88% of yield using [1,3-bis­(2,6- i Pr 2 C 6 H 3 )­imidazol-2-yilidene]­AuCl (5 mol %) from 1-(alkynyl)-7-oxabicyclo[4.1.0]­heptan-2-ones .…”

Pd/Cu-catalyzed access to novel 3-(benzofuran-2-ylmethyl) substituted (pyrazolo/benzo)triazinone derivatives: theirin silico/in vitroevaluation as inhibitors of chorismate mutase (CM)

“…1), we envisioned that the construction of the benzofuran ring could be a convenient as well as effective approach for serving the purpose. While numerous approaches are known for the construction of 2-substituted benzofuran ring, 17 the one-pot method [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] involving the tandem transition-metal-catalyzed Sonogashira cross-coupling 36 followed by intramolecular cyclization of 2-halogenated phenols with terminal alkynes gained considerable interest due to its convenience, functional group tolerance and environmental advantages. Indeed, one of us has been involved in exploring this strategy since 1992 (ref.…”

“…From the view point of reaction mechanism, 20,22–24,29,32 the involvement of two key steps e.g. Sonogashira coupling followed by intramolecular cyclization in the current approach are depicted in Scheme 2.…”

Synthesis of Bioactive Five- and Six-Membered Heterocycles Catalyzed by Heterogeneous Supported Metals

“…Park et al [70] developed Pd(OAC) 2 catalyst supported on NCBs and applied it for the synthesis of 2-substituted benzofuran from o-iodo phenol and various substituted terminal alkynes using Sonogashira cross-coupling reaction under copper and ligand-free condition. Park et al [70] developed Pd(OAC) 2 catalyst supported on NCBs and applied it for the synthesis of 2-substituted benzofuran from o-iodo phenol and various substituted terminal alkynes using Sonogashira cross-coupling reaction under copper and ligand-free condition.…”