Palladium-catalyzed direct arylation of thiazoles with aryl bromides

Catalytic Direct Arylation of Heteroaromatic Compounds

“…35 In this reaction, no monoarylated product is observed, even in the early stage of the reaction, suggesting that the second arylation proceeds relatively fast.…”

Five‐Membered Heterocycles: 1,3‐Azoles

“…However, although in particular cases it is possible to obtain the arylation with palladium in a regioselective form, in general, non-fused azoles gave mixtures of substitution at the 2-and/or 5-position and the use of bulky phosphines as ligands gives improved yields of diarylation [261].…”

Direct Transition Metal Catalyzed Functionalization of Heteroaromatic Compounds

“…26 The best yields of diarylated products were obtained by employment of bulky phosphine ligands (P(obiphenyl)( t Bu) 2 ) or P( t Bu) 3 in DMF at 150 °C. At the same time, arylation of thiazole 31 bearing a carboxanilide function as sacrificial group in less polar o-xylene afforded 4,5-diarylated thiazole 32 exclusively, (Scheme 12).…”

“…At the same time, arylation of thiazole 31 bearing a carboxanilide function as sacrificial group in less polar o-xylene afforded 4,5-diarylated thiazole 32 exclusively, (Scheme 12). 26 One of the first direct heteroarylations of heterocycles was reported in 1989 by Ohta who investigated palladium-catalyzed coupling of 2-chloro-3,6-dialkylpyrazines with protected indoles 33 (Scheme 13). 27,28 Reactions of 1-tosylindole with chloropyrazine in the presence of catalytic Pd(PPh 3 ) 4 led predominately to 3-heteroaryl indoles 34 in moderate to good yields.…”