Palladium-Catalyzed Synthesis of 3-Acylated Indoles Involving Oxidative Cross-Coupling of Indoles with α-Amino Carbonyl Compounds

Abstract

A new and selective C-N bond oxidative cleavage method to 3-acylated indoles by Pd-catalyzed oxidative cross coupling of indoles with α-amino carbonyl compounds has been developed; moreover, one-pot synthesis of 3-acylated indoles from 2-ethynylanilines and α-amino carbonyl compounds has also been established. Importantly, the products 3-acylated indoles can be used to construct polyheterocyclic compound, which can be employed as efficient probes for Hg(2+) and Fe(3+).

CuCl/air-mediated oxidative coupling reaction of imidazoheterocycles with N-aryl glycine esters

“…Replacing 2b with tertiary amine 2c caused the coupling reaction of 1a to 2c to selectively produce a diketone product 28 in 70% yield (eqn (2)). 16 These results are similar to those obtained from the coupling of indole to 2b reported by Li et al 17 Imidazoheterocycles with glycine motifs are of considerable interest to researchers and may have applications in biochemistry. Compound 3 was hydrolyzed to amino acid 29 (Scheme 3).…”

Strategies for Synthesis of Imidazo[1,2‐a]pyridine Derivatives: Carbene Transformations or C−H Functionalizations

“…Recently, Li et al. reported a Cu‐catalyzed oxidative cross‐coupling of indoles with α‐amino‐ketones to prepare 1,2‐dicarbonyl compounds 44 (Scheme a); In 2013, they also described a Pd‐catalyzed synthesis of 3‐acylated indoles 46 involving oxidative cross‐coupling of Indoles (Scheme b); Wu et al. developed I 2 ‐mediated direct regioselective oxidative cross‐coupling of indoles with methyl ketones to synthesize 1,2‐dicarbonyl Indoles 46 (Scheme c) .…”

Transition Metal‐Catalyzed CH Activation of Indoles

“…Reaction Couplingpartner/reagentC atalyst References 1a rylation aryl halides Pd [101,102,104,105] 2b enzoic acids Pd [107] 3a rylhydrazines Pd [108] 4c yclohexanones Pd [109] 5d iaryliodonium salts Cu [110] 6N -heterocyclic compounds Pd [111][112][113][114] 7a lkynylation alkynes Au [115] 8b enzylation benzylic alcohols Au [116] 9o lefination alkenes Pd [117,118] 10 acylation benzaldehydes Pd [119] 11 TMEDA Cu [120] 12 nitrilesP d [121] 13 CO and alcohols Rh [122] 14 a-amino carbonyl compounds Cu [123] 15 Pd [124] 16 synthesis of bisindoles alcohols Pd [141,142] 17 aldehydes Ag [143] 18 amines Pd [144] 19 annulation alkenes Pd 21 cyanation CuCN Pd [150] 22 K 4 [Fe(CN) 6 ]P d [151] 23 t-BuNC Pd [152] 24 NH 4 HCO 3 and DMSOP d [153] 25 amidation isocyanides Pd [154] Scheme 44. Pd-catalyzedarylation.…”

“…Thef ormation of 3-acylated indolesf rom indoles and a-aminocarbonyl substancesw as reported,e ither by Cu catalysis [123] as described by Lis group,o rb y Pd catalysis [124] as reported by Xianga nd Li, (Scheme 60a and b, respectively).…”