Synthesis of annulated benzimidazoles via amidine cyclization

An improved synthesis of telmisartan via the copper-catalyzed cyclization of o-haloarylamidines

“…[14][15][16][17] Considerable efforts have been devoted to the copper-catalyzed synthesis of benzimidazole derivatives, [18][19][20][21][22] in which the cyclization of ohaloarylamidines has drawn much attention. [23][24][25][26][27][28][29] Herein, we explored the idea to build the key bis-benzimidazole structure of telmisartan via the copper-catalyzed cyclization of o-haloarylamidines, 30,31 which were accessible to be obtained from ohaloarylamines (Scheme 2). This approach was suitable to produce telmisartan with good overall yield while avoiding the shortcomings associated with the reported routes.…”

Greener synthesis using hydrogen peroxide in ethyl acetate of alicyclic ring-fused benzimidazoles and anti-tumour benzimidazolequinones

“…3,16,29 There are drawbacks to reported syntheses of alicyclic ring-fused benzimidazoles such as requirements for transition metals, [1][2][3][4][5][6][7][8][9] prior synthesis of cyclization precursors, [10][11][12][13][14][15][16][17] full equivalents of strong base, [17][18][19][20] high molar mass hypervalent iodine reagents, 21 and the formation of mixtures of isomeric products. 22 The most convenient protocol remains the traditional oxidative cyclization of o-cyclic amine substituted anilines, which was first reported in the early 1960s using hydrogen peroxide in the presence of trifluoroacetic acid.…”

Peptidines: glycine-amidine-based oligomers for solution- and solid-phase synthesis

“…This transformation was accomplished with substantial generality using PCl 5 in refluxing benzene. 14 , 15 Although the poor hydrolytic stability of intermediate imidoyl chlorides precluded traditional work-up and purification protocols, 1 H-NMR analysis of crude reaction mixtures indicated ≥95% purity, alleviating the need for further purification. These intermediates were stable at room temperature for months without observable decomposition upon storage under moisture-free conditions as 1 M stock solutions in DCM.…”