Recyclable copper(i)-catalyzed coupling of 1-bromo-2-iodobenzenes and β-keto esters in bioderived 2-MeTHF: green synthesis of 2,3-disubstituted benzofurans

Abstract

A mesoporous SBA-15-anchored N-heterocyclic carbene (NHC)-copper(I) complex [SBA-15-NHC-CuI] was prepared via immobilization of 1,1′-(butane-1,4-diyl)bis(3-(3-(triethoxysilyl)propyl)-1H-imidazol-3-ium) chloride onto SBA-15, followed by reaction with CuI and NaO^tBu. With the use of SBA-15-NHC-CuI (10 mol% Cu) as a catalyst, the domino C–C/C–O coupling reaction between 1-bromo-2-iodobenzenes and β-keto esters proceeded smoothly in bioderived 2-MeTHF at 110 °C with K₂CO₃ as a base to deliver a wide array of 2,3-disubstituted benzofurans in good to high yields with a wide tolerance of functional groups. This new heterogenized NHC-copper(I) catalyst could be facilely recovered by centrifugation of the reaction mixture and recycled up to eight cycles without a significant loss of catalytic activity.