Synthesis and IR spectra of 2-phenylbenzimidazole and its amino derivatives

Product Class 4: Benzimidazoles

“…Typically, a 1-(acylamino)-or 1-(aroylamino)-2-aminoarene 31 is cyclized either by uncatalyzed thermolysis [192,193] or by treatment with aqueous or ethanolic acid [194] or phosphoryl chloride. [195] Hydrochloric, sulfuric, and phosphoric acids have been used successfully, but yields can vary considerably.…”

“…Benzimidazoles Made from 1-(Acylamino)-or 1-(Aroylamino)-2-aminoarenes [192,194,195,211,281] [192] H Ph H 4 M HCl 65 [194] H 3-H 2 NC 6 H 4 NH 2 4 M HCl 85 [194] H 4-H 2 NC 6 H 4 H 4 M HCl 75 [194] Me Me H 4 M HCl 2 [211] Bn Me H 4 M HCl 12 [211] H There are many examples of reactions that start with a 2-nitroaniline that is then acylated, reduced, and cyclized. [7,8] If the 2-nitroaniline has been acylated by ethyl chloroformate, the carbamate product can be catalytically reduced to the 2-aminocarbamate 31 (R 2 = OEt), which, on thermolysis, gives rise to a 1-substituted 1H-benzimidazol-2(3H)one.…”

“…2-(3-Aminophenyl)-1H-benzimidazol-5-amine (32, R 1 = H; R 2 = 3-H 2 NC 6 H 4 ; R 5 = NH 2 ): [194] A mixture of N 2 -(3-aminobenzoyl)benzene-1,2,4-triamine (24.2 g, 0.1 mol) and 4 M HCl (250 mL), or 1 M H 2 SO 4 (500 mL), was heated to its boiling point and maintained at that temperature for 0.5 h. After cooling, the precipitated salt was filtered and adjusted to pH 8.0±8.5 with 4 M NaOH, and the solid product was filtered off, washed with H 2 O, and dried at 102±105 8C, and then at 150 8C to remove H 2 O of crystallization, before final recrystallization (EtOH); yield: 19 g (85%); mp 257±258 8C. N-Alkyl-N-(ethoxycarbonyl)-2-nitroanilines; General Procedure: [197] A stirred soln of the 2-nitroaniline (20 mmol) and ethyl chloroformate (60 mmol) in xylene (30 mL) was heated for 14±18 h under reflux.…”