Non-directed Pd-catalyzed electrooxidative olefination of arenes Salman Ahsan 1 , Subir Panja 2 , Tanay Pal 1 , Simon Kolb 3 , Wajid Ali 1 , Sulekha Sharma 2 , Chandan Das 1 , Jagrit Grover 2 , Arnab Dutta 2 , Daniel B. Werz 3 , Amit Paul 2 , Debabrata Maiti 1 1 Indian Institute of Science Education and Research Bhopal, India, 2 IIT Bombay, India 3 Institute of Organic Chemistry, Germany The Fujiwara-Moritani reaction is a powerful tool for the olefination of arenes by Pd-catalyzed C–H activation. 1 Most of the methods for this exemplary reaction require the presence of directing groups on the substrate to address the low reactivity and regioselectivity. 2-3 We report here a ligand-enabled nondirected Pd-catalysed electrochemical C-H olefination of arenes and heteroarenes with excellent regioselectivity avoiding expensive silver salts, and high thermal energy that is sufficient enough to perturb the regio-selection since multiple C-H bonds of arenes are susceptible to activation. 4-5 The key findings of this work include: (i) the first report of electro- oxidative Pd-catalyzed non-directed olefination of arenes, (ii) highly regioselective olefination of (hetero)arenes, (iii) expensive and harmful chemical oxidant-free transformation, and (iv) exceedingly mild reaction conditions at 25 °C. The developed transformation provides an alternative route to conventional Fujiwara-Moritani reactions by substituting toxic chemical oxidants with electric current. The applicability of this non-directed approach was proven by broad substrate scopes and high regioselectivities. Preliminary mechanistic investigations suggested the involvement of a Pd(II)/Pd(IV) catalytic cycle via a Pd(III) intermediate. 6 References 1. Fujiwara, Y.; Moritani, I.; Danno, S.; Asano, R.; Teranishi, S., Aromatic substitution of olefins. VI. Arylation of olefins with palladium(II) acetate. Journal of the American Chemical Society 1969, 91 (25), 7166-7169. 2. Chen, Z.; Wang, B.; Zhang, J.; Yu, W.; Liu, Z.; Zhang, Y., Transition metal-catalyzed C–H bond functionalizations by the use of diverse directing groups. Organic Chemistry Frontiers 2015, 2 (9), 1107-1295. 3. Wedi, P.; van Gemmeren, M., Arene-Limited Nondirected C-H Activation of Arenes. Angew Chem Int Ed Engl 2018, 57 (40), 13016-13027. 4. Kubota, A.; Emmert, M. H.; Sanford, M. S., Pyridine Ligands as Promoters in PdII/0-Catalyzed C–H Olefination Reactions. Organic Letters 2012, 14 (7), 1760-1763. 5. Wang, P.; Verma, P.; Xia, G.; Shi, J.; Qiao, J. X.; Tao, S.; Cheng, P. T. W.; Poss, M. A.; Farmer, M. E.; Yeung, K. S.; Yu, J. Q., Ligand-accelerated non-directed C-H functionalization of arenes. Nature 2017, 551 (7681), 489-493. 6. Panja, S.; Ahsan, S.; Pal, T.; Kolb, S.; Ali, W.; Sharma, S.; Das, C.; Grover, J.; Dutta, A.; Werz, D. B.; Paul, A.; Maiti, D., Non- directed Pd-catalysed electrooxidative olefination of arenes. Chemical Science 2022, 13 (32), 9432-9439.
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