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Molecules 2008, 13(1), 149-156; doi:10.3390/molecules13010149
Article

Preparation of Second Generation Ionic Liquids by Efficient Solvent-Free Alkylation of N-Heterocycles with Chloroalkanes

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1 Dipartimento di Scienza e Tecnologia del Farmaco, Università di Torino, Via Giuria 9, 10125 Torino, Italy 2 Laboratoire de Chimie Moléculaire et Environnement, Polytech’Savoie, Université de Savoie, 73376 Le Bourget du Lac Cedex, France 3 DSM Nutritional Products, Research and Development, NRD/CC, Building-214/071, P.O. Box 3255, CH 4002-Basel, Switzerland
* Author to whom correspondence should be addressed.
Received: 24 December 2007 / Revised: 23 January 2008 / Accepted: 23 January 2008 / Published: 25 January 2008
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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-potsynthesis of second-generation ionic liquids (ILs), cutting down reaction times andimproving yields. However, the use of chloroalkanes in the alkylation of N-heterocyclesrequires more drastic conditions if results are to match those obtained with more reactivealkyl halides. The present paper describes a series of MW- or MW/US-promoted ILpreparations starting from chloroalkanes and classic heterocycles (1-methylimidazole,pyridine and 1-methylpyrrolidine). When reactions were carried out under conventionalheating in an oil bath they required longer reaction times and gave poorer yields. 1H-NMRanalysis and ion-exchange chromatography showed that the present solventless procedureafforded 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 achievedwith the use of alkyl chlorides, resulting in a considerable reduction of costs.
Keywords: Ionic liquids; chloroalkanes; one-pot reaction; microwaves; ultrasound. Ionic liquids; chloroalkanes; one-pot reaction; microwaves; ultrasound.
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Cravotto, G.; Gaudino, E.C.; Boffa, L.; Lévêque, J.-M.; Estager, J.; Bonrath, W. Preparation of Second Generation Ionic Liquids by Efficient Solvent-Free Alkylation of N-Heterocycles with Chloroalkanes. Molecules 2008, 13, 149-156.

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