Trihalide-based ionic liquids. Reagent-solvents for stereoselective iodination of alkenes and alkynes

Abstract

A study of the preparation of trihalide-based room temperature ionic liquids (ILs) has been made and the structure of trihalide ions has been investigated by electrospray ionization mass spectroscopy and NMR. The best procedure consists of mixing equimolar amount of ICl to [hmim][Cl] and IBr to [bmim][Br] or alternatively Cl₂ or Br₂ to [emim][I]. Trihalide ILs thus generated have been tested as reagent-solvents, or as reagents carrying out the reactions in [bmim][PF₆], in iodobromination as well as iodochlorination of alkenes and alkynes. Furthermore, the addition of ICl and IBr in [bmim][PF₆] was investigated. Yields of vic-iodochloro or iodobromo adducts from very good to almost quantitative are observed for all the substrates examined.