N-alkylation of benzimidazoles and benzotriazole via phase transfer catalysis

✍ Scribed by L.J. Mathias; D. Burkett

• Publisher: Elsevier Science
• Year: 1979
• Tongue: French
• Weight: 200 KB
• Volume: 20
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)86690-9

✦ Synopsis

Sumnary: N-methyl and other N-alkyl benzimidazoles and benzotriazoles were prepared by 18-crown-6 catalysis involving basic aqueous solutions of the heterocycles and organic solutions of alkyl iodides or bromides. In the course of our work with highly substituted benzimidazoles, we required a mild, clean procedure for introducing methyl and benzyl groups onto the heterocycle nitrogens. Available methods involving refluxing CH31 in CH30H1 or dimethyl sulfate* were unsatisfactory, often leading to large yields of the unwanted N,N'-disubstituted quanternary salts 1. We describe here a new procedure for such alkylations involving phase transfer catalysis with 18-crown-6 (2). 1 " 2 3 A typical meth>ation involves dissolving 0.5 g of a benzimidazole 4 or benzotriazole 3 in 5 ml of 3-6N KOH, adding 1.1 eq. CH31 in Ccl4 followed by 0.05 -0.1 eq. 2. Stirring rapidly for 4-24 hours leads to essentially complete conversion. The Table lists the reactions examined for 2 and several derivatives of 4.