Arene borylation through C H activation using Cu3(BTC)2 as heterogeneous catalyst

α,β-Enone Borylation by Bis(Pinacolato)Diboron Catalyzed by Cu3(BTC)2 Using Cesium Carbonate as a Base

“…These results clearly indicate that this reaction is promoted efficiently with Cu 2+ as active sites, while other MOFs with Cr 3+ and Zn 2+ are ineffective for this transformation under these reaction conditions. These results are also in agreement with a previous report where the C-H borylation reaction of arene with B 2 pin 2 was promoted by Cu 3 (BTC) 2 while other MOFs failed to provide the desired product [41]. Although enantioselective borylation of 2-cyclohexenone with B 2 pin 2 was reported by CuCl using NaOt-Bu in MeOH/THF at a 92% yield with 98% ee [18], CuCl in the presence of cesium carbonate gives less than one half of the yield achieved with Cu 3 (BTC) 2 in the present work.…”

“…Similarly, other related MOFs like Al(OH)(BDC) (BDC: 1,4-benzenedicarboxylate) and ZIF-8 with the trade names Basolite A100 and Basolite Z1200, respectively were also purchased from Sigma Aldrich, Barcelona, Spain. MIL-101(Cr) was synthesized by adopting earlier procedure, and its structural integrity was confirmed by powder X-ray diffraction (XRD), which was in good agreement with an earlier report [41]. Furthermore, CuCl, Cu(NO 3 ) 2 .3H 2 O, Cs 2 CO 3 , K 2 CO 3 , Na 2 CO 3 , B 2 pin 2 , 2-cyclohexenone and acetonitrile were procured from Sigma Aldrich, Barcelona, Spain.…”

“…incorporation of B2pin2 shows spectroscopic changes compatible with the formation of Cu-Bpin and the weakening of the Cu-Cu bond [41]. These spectroscopic signatures are reversed upon the desorption of Bpin by thermal evacuation under vacuum [41]. Additionally, the fact that the product yield is not affected by the presence of 2,6-di-t-butyl-4-methylphenol (Entry 15, Table 1) and TEMPO (Entry 16, Table 1) that are typical C-centred radical quenchers, thus ruling out the reaction mechanism involving carbon radicals.…”

“…incorporation of B2pin2 shows spectroscopic changes compatible with the formation of Cu-Bpin and the weakening of the Cu-Cu bond [41]. These spectroscopic signatures are reversed upon the desorption of Bpin by thermal evacuation under vacuum [41].…”

“…Therefore, Cu 3 (BTC) 2 has been widely used as a catalyst to promote a variety of Lewis acidcatalyzed organic reactions including condensation [28], the ring opening of epoxide [29], and cyclizations [30][31][32], among others [33][34][35]. Furthermore, Cu 2+ ions in Cu 3 (BTC) 2 MOF with unsaturated positions have also been reported in many organic transformations like the oxidation of styrene [36], aerobic epoxidation of olefin [37], CO oxidation [38], oxidative synthesis of quinazolinones [39], synthesis of tetrazoles [40], arene borylation [41], Friedel-Crafts alkylation of indoles with nitroalkenes [42], dehydrogenative coupling of dimethylphenylsilane with phenol [43], acetalization of benzaldehyde [44], aldol synthesis of pyrimidine-chalcone hybrids [45], and hydrogenation of acetophenone by silanes [46].…”