title: Preparation of second generation ionic liquids by efficient solvent-free alkylation of N-heterocycles with chloroalkanes.
abstract: Non-conventional techniques, such as microwave (MW) and power ultrasound (US) as well as combined MW/US irradiation, have been used to promote one-pot synthesis of second-generation ionic liquids (ILs), cutting down reaction times and improving yields. However, the use of chloroalkanes in the alkylation of N-heterocycles requires more drastic conditions if results are to match those obtained with more reactive alkyl halides. The present paper describes a series of MW- or MW/US-promoted IL preparations starting from chloroalkanes and classic heterocycles (1-methylimidazole, pyridine and 1-methylpyrrolidine). When reactions were carried out under conventional heating in an oil bath they required longer reaction times and gave poorer yields. (1)H-NMR analysis and ion-exchange chromatography showed that the present solventless procedure afforded ILs of satisfactory purity. The observed high yields (usually 70-98% isolated), and short reaction times showed that a straightforward access to ILs can be also achieved with the use of alkyl chlorides, resulting in a considerable reduction of costs.
authors.affiliation: Dipartimento di Scienza e Tecnologia del Farmaco, Università di Torino, Via Giuria 9, 10125 Torino, Italy. giancarlo.cravotto@unito.it
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Cravotto
authors.forename: Emanuela Calcio
authors.initials: EC
authors.lastname: Gaudino
authors.forename: Luisa
authors.initials: L
authors.lastname: Boffa
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Lévêque
authors.forename: Julien
authors.initials: J
authors.lastname: Estager
authors.forename: Werner
authors.initials: W
authors.lastname: Bonrath
mesh_terms: D000478:Alkylation; D017606:Chlorine Compounds / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry*; D052578:Ionic Liquids / Q000138:chemical synthesis*; D008872:Microwaves; D012997:Solvents / Q000737:chemistry*; D014465:Ultrasonics
chemical_list: D017606:Chlorine Compounds; D006571:Heterocyclic Compounds; D052578:Ionic Liquids; D012997:Solvents