Synthesis of Halogen Derivatives of N-Methylimidazole

Abstract

A. R. Egypt Bromo, iodo, fluoro and mixed halogen derivatives of N-methylimi-dazole (NMI) were prepared in good yields by direct halogenation. The reactivity of NMI ring towards halogenation was investigated. Structural assignments of the new halogen NMI derivatives were confirmed by their 1 H NMR spectra. Previously 1-•> some bromo and iodo NMI compounds have been prepared by tedious procedures and in poor yields. In the present work bro-mination of NMI ring was performed smoothly either by N-bromosuccin-imide (NBS), or by organo-lithium intermediate to yield compounds 1-7 (Scheme 1). 2-Bromo NMI (1) 1 .1> has been prepared in high yield (800/o) by successive action of butyllithium (BuLi) on NMI followed by bromine. This result indicates that the reaction is regiospecific and position two is the more reactive one. NBS afforded a mixture of bromo derivatives, but when equimolecular quantities were used 5-bromo NMI (3) predominated. Similarly, iodo NMI derivatives 8-14 were prepared in good yields by either butyllithium and iodine or iodine and iodic acid (Scheme 2). Scheme 1 Buli t N Br2 ~~Br 1 CH3 ł NBS ~~ (IJ8uLi,llllH20 Br ~ Br 5 CH3 Bulił Br2 Br t\ lllBuLi,llllH20 ~ Br 4 CH~ NBS Br)-N Br)-N 1'.. .. > (IJBuLi,(llJH 2 o ~ A BrN BrN Br 6 tH3 7 tH3