Domino synthesis of 2-arylbenzo[b]furans by copper(II)-catalyzed coupling of o-iodophenols and aryl acetylenes

Facile synthesis of 2-substituted benzo[b]furans and indoles by copper-catalyzed intramolecular cyclization of 2-alkynyl phenols and tosylanilines

“…When the experiment was carried out in the absence of CuCl, no reaction took place aer 24 h (entry 24), which suggested that copper catalyst was essential for this conformation although recently Gao and coworkers reported that this reaction could be completed at a higher temperature without any transition metal catalyst. 14 Compared with other copper-catalyzed methods for benzo [b] furan synthesis, [11][12][13]15 our optimized conditions featured lower catalyst and base loading, ambient temperature and ligand free.…”

“…10 For example, Venkataraman and coworkers accomplished the synthesis of 2-arylbenzo[b]furans by exposing aryl acetylenes and 2-iodophenols to 10 mol% [Cu(phen) (PPh 3 ) 2 ]NO 3 and 2 equivalents of Cs 2 CO 3 in toluene at 100 C for 24 h. Similar transformations were realized with copper pincer complexes by Domínguez 11 and with Cu(OTf) 2 -BINAM by Sekar. 12 2-Substituted indoles can also be obtained aer the reaction of 2-ethynylaniline derivatives under reux in Cu(OCOCF 3 ) 2 aqueous solution for 24 h. 13 However, high reaction temperature and the use of stoichiometric amount of base are usually unavoidable to achieve high yields in these reactions. Herein, we report a facile and inexpensive method for the synthesis of 2-substituted benzo[b]furans and indoles by copper-catalyzed intramolecular cyclization of 2-alkynyl phenols and tosylanilines under mild conditions.…”

One‐Pot Synthesis of Benzofurans via Cu–Catalyzed Tandem Sonogashira Coupling‐Cyclization Reactions

“…This interesting preliminary finding motivated us to check the effect of different bases on the outcome of the reaction 13,14,11,12). We have also carried out some blank experiments and as expected, the reaction did not proceed in the absence of catalyst or ligand (entries 18 & 19).…”

“…The first Cu‐catalyzed one‐pot method for the synthesis of benzofurans was reported by Venketaraman's group in 2002 . A few years later Cu(II) dibenzyl BINAM based ligand was also reported for this purpose . Recently a CuI 2 (pip) 2 ‐catalyzed one‐pot method was developed by Chen's group and they explored the mechanism of the reaction using DFT studies .…”

“…[12] A few years later Cu(II) dibenzyl BINAM based ligand was also reported for this purpose. [13] Recently a CuI 2 (pip) 2 -catalyzed one-pot method was developed by Chen's group and they explored the mechanism of the reaction using DFT studies. [14] However these protocols were limited to the coupling of 2-iodophenols only.…”