Azines polycycliques. (IV). Synthèse de dérivés sulfurés en —3 de l'imidazo[1,5‐a]pyridine

Abstract

La dihydro‐2,3 imidazo[1,5‐a]pyridinethione‐3 est ‐préparée aisément à partir de l'aminométhyl‐2 pyridine et est ensuite S‐alkylée ou ‐aralkylée. On décrit, dans le cas du dérivé 3‐thiométhylé, la trifluoroacétylation en ‐1,l'oxydation en méthylsulfone et l'hydrolyse des trifluorocétones en acides alkylthio‐3 et alkylsulfonyl‐3 imidazo[1,5‐a]pyridine carboxyliques‐1.

Product Class 5: Azaindolizines with Two Nitrogen Atoms in the Five-Membered Ring

“…Pyridin-2-amines can be acylated by acids, anhydrides, or acid chlorides, and the acylamino compounds so obtained, when treated with a water-withdrawing agent like strong acid, inorganic acid chloride, or dicyclohexylcarbodiimide, undergo ring closure, generally in good yields. [149] 2-[(Thioacetylamino)methyl]pyridine (189), prepared from 2-(aminomethyl)pyridine (188) and ethyl dithioacetate, reacts with mercury(II) oxide to give 3methylimidazo[1,5-a]pyridine (190) in moderate yield. 2-(Aminomethyl)pyridine (179) reacts with either acids or acid chlorides and affords 3-substituted imidazo[1,5-a]pyridines (180).…”

“…Examples of this reaction are shown in Scheme 31. [139] Scheme 32 Ring Closures of Various (Acylaminomethyl)pyridines To Give Fused Imidazoles [139,148,149] [137] A mixture of 2-(formamidomethyl)pyridine (1.95 g, 14.3 mmol), POCl 3 (6.58 g, 43 mmol), and benzene (12 mL) was refluxed for 4 h. The mixture was evaporated in vacuo, the residue was decomposed with H 2 O, basified, and extracted (CHCl 3 ). [137,145] The same approach can usefully be applied for the synthesis of benzo ana-logues: 1-(aminomethyl)isoquinoline (181) when treated with propyl formate (182) and, subsequently, with formic acid yields the tricyclic imidazole-fused product 183 in good yield.…”