Electrooxidative Rhodium‐Catalyzed C−H/C−H Activation: Electricity as Oxidant for Cross‐Dehydrogenative Alkenylation

Abstract

Rhodium(III) catalysis has enabled ap lethora of oxidative CÀHf unctionalizations,w hich predominantly employs toichiometric amounts of toxic and/or expensive metal oxidants.I nc ontrast, we herein describe the first electrochemical rhodium-catalyzed C À Ha ctivation that avoids hazardous chemical oxidants.E nvironmentally benign twofold C À H/C À Hfunctionalizations were accomplished with weakly coordinating benzoic acids and benzamides,employing electricity as the terminal oxidant and generating H 2 as the sole byproduct.

Nickel‐Catalyzed Electrooxidative C−H Amination: Support for Nickel(IV)

“…To this end, we first conducted intermolecularc ompetition experiments( Scheme 4a). In contrastt oa ll previously reportede lectrooxidative CÀHa ctivations with palladium, [5] rhodium, [6] ruthenium, [7] iridium, [8] or cobalt catalysts, [9,10] the more electron-deficient arenesr eacted faster here. These findings are indicative of ac oncerted-metal-ation-deprotonation mechanism [18] being operative in the CÀH metalation.I ng ood agreement with this observation, we, second, did not find H/D scrambling when using D 3 COD as the cosolvents (Scheme 4b).…”

“…Combining metal-catalyzed CÀHa ctivation [1] with electrocatalysis [2] holds transformativep otential for molecular syntheses, [3] because it circumventst he use of toxic ande xpensive metal oxidants. [4] The use of electricity as formal oxidantf or CÀHa ctivation is likewise attractive since it allows the sustainableu se of renewablee nergy.W hile this approach considerably improvedt he atom-economy of CÀHa ctivation, advancesw ere until very recently largely limited to the precious 4d metals palladium, [5] rhodium, [6] ruthenium, [7] and iridium. [8] In sharp contrast, only very recentlyw eh ave unraveled the potential of cobalt catalysts for electrochemical CÀHf unctionalizations, [9] which has proven instrumental for cobalt-mediated transformations.…”

Electrochemical Oxidation Dearomatization of Anisol Derivatives toward Spiropyrrolidines and Spirolactones

“…In recent years, electrochemical synthesis has been widely recognized as an efficient and environmentally benign synthetic tool in synthetic chemistry. [24][25][26][27][28][29][30][31][32][33][34] With sufficient potential bias, organic substrates can lose electrons at the anode to generate highly reactive intermediates, which is superior than the classical reactions involving chemical oxidants. Compared with the well-versed chemical dearomative procedures, few sustainable electrochemical versions have been validated.…”

Electrochemical Oxidative Clean Halogenation Using HX/NaX with Hydrogen Evolution

“…Electrochemical anodic oxidation presents the prospect of the efficient and environmentally benign synthesis of complex molecules and has attracted considerable interest (Tang et al., 2018a, Yoshida et al., 2018, Jiang et al., 2018, Yan et al., 2017, Pletcher et al., 2018, Francke and Little, 2014, Jutand, 2008, Sperry and Wright, 2006, Qiu et al., 2018, Xiong et al., 2017, Gieshoff et al., 2017, Fu et al., 2017b, Yang et al., 2017, Horn et al., 2016, Badalyan and Stahl, 2016, Kärkäs, 2018, Liu et al., 2018, Lyalin and Petrosyan, 2013, Raju et al., 2006, Kulangiappar et al., 2016, Tan et al., 2017). As part of our continuing studies in the area of electrochemical oxidative C-C and C-heteroatom bonds formation (Yuan et al., 2019, Tang et al., 2018b, Gao et al., 2018, Yuan et al., 2018a, Yuan et al., 2018b, Yuan et al., 2018c), we herein report a clean halogenation by exogenous-oxidant-free electrochemical oxidation.…”