Regiospecific Synthesis of 3-Substituted Imidazo[1,2-a]pyridines, Imidazo[1,2-a]pyrimidines, and Imidazo[1,2-c]pyrimidine

Abstract

3-Substituted imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, and imidazo[1,2-c]pyrimidine were obtained regiospecifically in yields of 35-92% in one pot by reaction of 2-aminopyridines or 2-(or 4-)aminopyrimidines, respectively, with 1,2-bis(benzotriazolyl)-1,2-(dialkylamino)ethanes.

6-Bromo-2-(4-chlorophenyl)-3-methyl-3H-imidazo[4,5-b]pyridine

“…Many imidazopyridines have a significant inhibitory effect on many target enzymes (Palmer et al 2007;Katritzky et al 2003), as well as anti-viral, antibacterial, anti-microbial and anti-cytokinin activity. Some of them can be used to treat peptic ulcers, diabetes and mental illness (Scribner et al 2007, Liang et al 2007.…”

Fast and efficient direct conversion of 2-aminopyridine into 2,3-disubstituted imidazo[1,2-a]pyridines

“…R f 0.27 (acetone:CH 2 Cl 2 5:95); mp 115.5-115.7 o C. 1 H NMR 1.841 (d, 3H, J 7.4, CH 3 ), 5.048 (q, 1H, J 7.4, CH-CH 3 ), 6.592 (td, 1H, J 1.2, 6.9, CH-6), 7.140 (ddd, 1H, J 1.1, 6.9, 9.0, CH-7), 7.269 (m, 3H, CH-2, CH-4 and CH-6 of Ph-3), 7.339 (tt, 2H, J 1.9, 7.2, CH-3 and CH-5 of Ph-3), 7.403 (tt, 1H, J 1.9, 7.4, CH-4 of Ph-2), 7.483 (tt, 2H, J 1.6, 7.0, CH-3 and CH-5 of Ph-2), 7.627 (dt, 1H, J 1.1, 6.9, CH-5), 7.679 (dt, 1H, J 1.2, 9.0, CH-8), 7.778 (dt, 2H, J 1.4, 6.9, CH-2 and CH-6 of Ph-2). 13 -1-yl)-3-(1-(naphthalen-1-yl) 1,6.8,7.177 (ddd,1H,J 1.1,6.7,9.0,7.264 (tt,1H,J 1.3,7.3, CH-4 of Ph-2), 7.333 (m, 5H, CH-3 and CH-5 of Ph-2 and CH-3, CH-4 and CH-5 of Ph-3), 7.387 (dt, 2H, J 1.3, 7.0, CH-2 and CH-6 of Ph-3), 7.634 (dt,1H,J 1.1,6.9,7.685 (dt,1H,J 1.0,9.0,7.934 (dt,2H,J 1.9,7.1, CH-2 and CH-6 of Ph-2). 120.12 (C quat .039 (ddd, 1H, J 1.4, 6.4, 7.1, CH-7), 6.723 (dd, 1H, J 1.4, 9.1, CH-9), 6.743 (dd, 1H, J 1.5, 7.1, CH-6), 6.962 (ddd, 1H, J 1.5, 6.4, 9.1, CH-8), 7.636 (tt, 2H, J 1.9, 8.9, CH-2 and CH-6 of 4-NO 2 Ph-4), 7.834 (tt, 2H, J 1.9, 8.9, CH-2 and CH-6 of 4-NO 2 Ph-2), 8.093 (tt, 2H, J 1.9, 8.9, CH-3 and CH-5 of 4-NO 2 Ph-2), 8.173 (tt, 2H, J 1.9, 8.9, CH-3 and CH-5 of 4-NO 2 Ph-4).…”

“…120.12 (C quat .039 (ddd, 1H, J 1.4, 6.4, 7.1, CH-7), 6.723 (dd, 1H, J 1.4, 9.1, CH-9), 6.743 (dd, 1H, J 1.5, 7.1, CH-6), 6.962 (ddd, 1H, J 1.5, 6.4, 9.1, CH-8), 7.636 (tt, 2H, J 1.9, 8.9, CH-2 and CH-6 of 4-NO 2 Ph-4), 7.834 (tt, 2H, J 1.9, 8.9, CH-2 and CH-6 of 4-NO 2 Ph-2), 8.093 (tt, 2H, J 1.9, 8.9, CH-3 and CH-5 of 4-NO 2 Ph-2), 8.173 (tt, 2H, J 1.9, 8.9, CH-3 and CH-5 of 4-NO 2 Ph-4). 13 …”

“…7 A number of methods have been developed for the synthesis of this important framework; the most exploiting 2-aminopyridine as starting material. The main part of the protocols involves initial coupling reactions between endocyclic nitrogen of 2-aminopyridine and various reagents, such as α-halocarbonyl compounds, 8 diazoketones, 9 oxothioamide, 10 1,2-diols, 11 1-chloromethylbenzotriazole, 12 1,2-bis(benzotriazolyl)-1,2-(dialkylamino)-ethanes, 13 followed by cyclization with the exocyclic amino group. However, these approaches generally suffer from…”

Aqueous phase synthesis of bridgehead azaheterocycles in the presence of β-cyclodextrin

“…9 Imidazo [1,2-a]pyridines are also an important pharmocophore in a number of drug formulations currently available in the market. 10 Apart from the above, imidazo[1,2-a]pyridinium salts are also used to prepare styryl dyes. …”