Ruthenium-Catalyzed Regioselective C–H Bond Acetoxylation on Carbazole and Indole Frameworks

Abstract

The regioselective C-H bond cleavage/C-O bond formation takes place smoothly upon treatment of 9-(pyridin-2-yl)carbazoles with acetic acid in the presence of a silver salt oxidant under ruthenium catalysis to afford the corresponding C1- and C8-diacetoxylated products. Under similar conditions, the acetoxylation of 2-aryl-1-(pyridin-2-yl)indoles as well as 1-aryl-7-azaindoles can also be conducted efficiently.

A comprehensive overview of directing groups applied in metal-catalysed C–H functionalisation chemistry

“…Finally, the acetoxylation of indoles (2-substituted, C7 functionalisation) and carbazoles was reported by Miura using acetic acid, Ru catalysis, and Ag oxidant ( Scheme 127E ). 771 It is worth noting that the functionalisation of unsubstituted indoles was not observed, either in C7 or in C2.…”

Aerobic C–H Oxidation of Arenes Using a Recyclable, Heterogeneous Rhodium Catalyst

“…The combined organic layer was washed with brine, dried over Na 2 SO 4 , and filtered, and the solvent was evaporated to afford the crude product, which was purified by silica gel column chromatography (AcOEt/hexane 20%) to yield 45 mg (76%) of 4a as yellow-green solids. 1 H NMR (600 MHz, CDCl 3 ): δ 8.22 (1H, s), 8.05 (1H, s), 7.94 m),7.81 (1H,d,J = 8.4 Hz),7.77 (1H,d,J = 8.4 Hz),7.54 (1H,t,J = 8.4 Hz),7.45 (1H,t,J = 8.4 Hz),7.34 (1H,d,J = 8.4 Hz), 2.16 (3H, s). 13 C NMR (150 MHz, CDCl 3 ): δ 151.8 (s), 140.5 (s, q: J C−F = 35 Hz), 126.8 (s), 124.1 (s), 120.2 (s), 119.2 (d), 118.7 (s), 118.3 (d), 117.5 (d), 116.3 (d), 115.9 (d), 114.1 (s), 113.8 (s), 112.1 (d), 111.1 (d), 107.4 (s, q: J C−F = 229 Hz), 101.7 (d), 34.7 (q).…”

Transition‐Metal‐Catalyzed Directing Group Assisted (Hetero)aryl C−H Functionalization: Construction of C−C/C‐Heteroatom Bonds

“…Concurrently, Ackermann group demonstrated the use of O ‐tethered 2‐pyridyl DG for the ortho ‐selective C−H acyloxylation using broad range of carboxylic acids under Ru‐catalysis employing AgSbF 6 as the additive and K 2 S 2 O 8 as the oxidant [42] . In addition, Shi group [43] reported a copper‐catalyzed acyloxylation of benzamides using N,N ‐bidentate directing group while Miura group [44] utilized the Ru‐catalysis for the C−H acetoxylation of indole and carbazole scaffolds utilizing Ag 2 CO 3 as the oxidant at elevated temperature (Scheme 9C–D). Later, Li group disclosed a Rh‐catalyzed pyridyl‐directed strategy for C−O bond formation by exploiting various carboxylic acids as the coupling partners in the presence of AgF as the oxidant (Scheme 9E) [45] …”