Copper-catalyzed tandem cyclization of 2-(2-iodophenyl)imidazo[1,2-a]pyridine derivatives with selenium: Synthesis of benzo[b]selenophene-fused imidazo[1,2-a]pyridines

Recent Advances in the Synthesis of Selenophenes and Their Derivatives

“…Similarly, in recent years, several protocols have been described for the synthesis of fused benzoselenophene derivatives through TM-catalyzed tandem cyclization reactions, employing ortho -haloarene heterocycles and elemental selenium. In this context, in 2016, the Cu-catalyzed tandem cyclization of 2-(2-iodophenyl)imidazo[1,2- a ]pyridines 115 with selenium, for the synthesis of benzo[ b ]selenophene-fused imidazo[1,2- a ]pyridines 116 via Ullmann-type Se -arylation and C( sp 2 )-H selenylation was described ( Scheme 75 ) [ 167 ]. The reaction was performed using CuI (10 mol%) as the catalyst, under aerobic conditions in DMSO at 130 °C.…”

Synthesis of 2-Aryl-3-(arylselanyl)imidazo[1,2-a]pyridines: Copper­-Catalyzed One-Pot, Two-Step Se-Arylation of Selenium with Imidazopyridines and Triarylbismuthanes

“…On the other hand, when N,N,N,′N′-tetramethylethylenediamine (TMEDA) was used instead of 1,10-phenanthroline, selenide 3a was formed as the major product and diselenide 2a was not obtained (entry 11). The screening of solvents showed that the reaction proceeded most efficiently in DMSO (87%), whereas other solvents gave disappointing results (entries 1 and [16][17][18][19][20][21][22]. A significant decrease in the yield of 2a was observed under Ar and O 2 atmospheres (entries 23 and 24).…”

Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs2CO3-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium

“…For example, the reaction of 2-(2-iodophenyl)indoles with selenium powder in the presence of CuO as catalyst resulted in benzoselenopheno[3,2- b ]indole derivatives [14]. The reaction of 2-(2-haloaryl)imidazo[1,2- a ]pyridines with selenium using a CuI catalyst for the synthesis of benzo[ b ]selenophene-fused imidazo[1,2- a ]pyridines occurred smoothly [15–16]. Performing these types of reactions without the addition of a transition metal catalyst is more challenging, but would alleviate the environmental burden of removing and disposing of the metal catalyst.…”