Palladium‐Catalyzed Direct C2 Arylation of N‐Substituted Indoles with 1‐Aryltriazenes

Abstract

A novel and efficient palladium-catalyzed C2 arylation of N-substituted indoles with 1-aryltriazenes for the synthesis of 2-arylindoles was developed. In the presence of BF3⋅OEt2 and palladium(II) acetate (Pd(OAc)2), N-substituted indoles reacted with 1-aryltriazenes in N,N-dimethylacetamide (DMAC) to afford the corresponding aryl-indole-type products in good to excellent yields.

Exploration of Biaryl Carboxylic Acids as Proton Shuttles for the Selective Functionalization of Indole C–H Bonds

“…The product was isolated by column chromatography (PE:EA = 100:1) as a light yellow solid (51.6 mg, 69%). Spectral data is consistent with previous reports …”

“…The compound was prepared following the general procedure using methyl 1-methylindole-4-carboxylate and 1-bromo-4-methoxybenzene as reactants. The product was isolated by column chromatography (PE:EA = 20:1) as a light yellow solid (49.6 mg, 56%) Spectral data is consistent with previous reports …”

Polarclean/Water as a Safe and Recoverable Medium for Selective C2-Arylation of Indoles Catalyzed by Pd/C

“…When the reaction is performed in the absence of Pd/C, the thermal reaction is not effective at 70 °C (entry 18, Table ); the formation of the C-3 product provides support for an electrophilic palladiation mechanism at C-3 followed by a 1,2-migration of palladium to the C-2 position that involves classic Pd(0)/Pd­(II) catalytic cycles. − …”

Palladium Catalyzed Electrophilic C2‐Arylation of Azoles by Aryltriazenes in Ionic Liquid Promoted by Acidic Ionic Liquid

“…Direct coupling protocols that unite the azole based heterocycles with diverse aryl counter parts remain mainstay transformation as it avoids the need for stoichiometric amount of aryl‐metal reagents. Of the numerous methods developed over the decades to synthesize these compounds of interest, the C(2)‐H activation of the azole rings gains significance among the chemists and in particular activation effected by transition metal catalyzed arylation at C(2) position in azole frameworks is of considerable importance . This metal catalyzed direct arylation strategy employs aryl electrophiles such as aryl‐halides,‐triflates,‐sulfinates and organoboranes etc.…”