Aerobic homocoupling of arylboronic acids catalysed by copper terephthalate metal–organic frameworks

Abstract

Copper terephthalate MOF is utilised as an environmentally benign, efficient and reusable heterogeneous catalyst to effect the aerobic homocoupling of arylboronic acids yielding the corresponding symmetrical biphenyls under mild reaction conditions. This method tolerates various substituents present in arylboronic acids such as halogens, cyano and nitro groups. The catalytic performance has been compared with that of other copper based MOFs namely MOF-101, [Cu(pdc) 2 ]NH 2 Me 2 , [Cu 2 (ndc) 2 ted] n and [Cu(H 2 L)] n as well as with other copper salt catalysts. Sheldon test confirmed the heterogeneity of the catalyst, which can be reused under optimized conditions with only a minor loss in its activity. A mechanism for the homocoupling reaction is also proposed. The simplicity of catalyst preparation, its stability, substrate selectivity, easy recovery and regeneration designate possible utilization of this catalytic system in a multitude of catalytic reactions and industrial processes. † Electronic supplementary information (ESI) available. See

Framework‐Copper‐Catalyzed C−N Cross‐Coupling of Arylboronic Acids with Imidazole: Convenient and Ligand‐Free Synthesis of N‐Arylimidazoles

“…However, the catalyst was sensitive to water, and a notable decrease in the yield was observed if an aqueous mixture of solvents was used. The catalyst was highly specific towards N‐arylation, and no other homocoupling or conversion of the C−B bond into a C−O bond was found with any protic polar solvents, which was observed in previous studies under identical conditions . The reaction was highly time dependent, and shorter reaction times result in moderate conversions (Table , entry 10), whereas reaction times of 12 h afford an excellent yield of 99 % without any byproducts.…”

“…The exposed apical Cu 2+ coordination sites, high surface area, and large pore volume of Cu(tpa)‐MOF will be expected to catalyze the N ‐ arylation of imidazole using arylboronic acids as electrophiles. Except for very few reports on the application of Cu(tpa)‐MOF in organic synthesis, to the best of our knowledge this is the first report of Cu(tpa)‐MOF as a catalyst for the synthesis of N‐arylimidazoles by C−N cross‐coupling.…”

Engineering Metal–Organic Framework Catalysts for C−C and C−X Coupling Reactions: Advances in Reticular Approaches from 2014–2018

“…[51] MOF-74i sh ighly nanocrystalline, with crystal sizes ranging from 35 to 50 nm and surface areas as high as 1010 m 2 g À1 .D ang and co-workers [52] used Cu-MOF-74 to produce substituted indolizines through ao ne-pot amine-aldehyde-alkyne couplingr eaction. Puthiaraj and co-workers [53] reported the use of aC u-terephthalate framework for aerobic Suzuki coupling reactions. The MOF had aB ET surface area of 1100 m 2 g À1 with ap ore volume of 0.50 cm 3 g À1 .C u-MOF-74 synthesized in this regard had an unusually high thermal stability (exceeding3 00 8C) and ac opperc ontento f3 6.51 %.…”

Novel visible-light-responsive Ag/AgCl@MIL-101 hybrid materials with synergistic photocatalytic activity

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