Palladium-catalyzed decarboxylative C2-acylation of indoles with α-oxocarboxylic acids

Abstract

A palladium-catalyzed decarboxylative C2-acylation of indoles with α-oxocarboxylic acids was achieved. This protocol represents a novel and complementary approach to 2-aroylindoles.

Palladium‐Catalyzed C2‐Acylation of Indoles with α‐Diketones Assisted by the Removable N‐(2‐Pyrimidyl) Group

“…α-Diaryl ketones that possess electron-withdrawing groups (3c and 3f) gave higher yields than those with electron-donating groups (3b, 3d, and 3e). The use of electron-donating indoles with methyl (1e and 1j) and methoxy (1f) substituents gave corresponding products 3l, 3q, and 3m, respectively, in good yields (Table 2, Entries 12,13,and 17), whereas indoles with electron-withdrawing groups, such as fluoro, chloro, bromo, nitrile, and methyl ester, provided the corresponding products in moderate to good yields ( Table 2, Entries 9-11 and [14][15][16]. Under standard reaction conditions, challenging 2,3-butanedione 2g and 3,4-hexanedione 2h also afforded products 3g and 3h in 67 and 71 % yields, respectively.…”

“…[11] The coupling of nitrogen-protected 2-lithioindoles with acyl chloride is a common method for their synthesis, [12] however, this method suffers from air-and moisture-sensitive organolithium reagents. [14] Recently, Saxena [15] and Zhu [16] reported palladium-catalyzed decarboxylative C2 acylation of indoles by using α-oxocarboxylic acids under different conditions. Beller and co-workers described an efficient ruthenium-catalyzed carbonylative C-H-bond arylation process to provide 2-acylindole derivatives, however, the essential use of carbon monoxide limits the application of this method.…”

Palladium(II) Acetate

“…MeAcylation of Indoles.A decarboxylative direct arylation of indoles containing a pyrimidyl directing group was reported (eq 158) 282. …”

Palladium‐Catalyzed Direct C2‐ and Further C7‐Acylation of Indoles with Aldehydes

“…[8] In both cases, a large excess of expensive silver carbonate was used as oxidant. Recently, palladium-catalyzed direct acylation of arenes with aldehydes has provided an efficient route to aryl ketones.…”