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Brønsted Acidic Ionic Liquid Accelerated Halogenation of Organic Compounds with N-Halosuccinimides (NXS)
Laboratory for Organic and Bioorganic Chemistry, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
Faculty for Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, 1000 Ljubljana, Slovenia
Department of Chemistry, University North Florida, Science and Engineering Building, 1 UNF Drive, Jacksonville, FL 32224, USA
Centre of Excellence for Integrated Approaches in Chemistry and Biology of Proteins CIPKeBiP, Jamova 39, 1000 Ljubljana, Slovenia
* Author to whom correspondence should be addressed.
Received: 15 November 2012; in revised form: 6 December 2012 / Accepted: 11 December 2012 / Published: 21 December 2012
Abstract: The Brønsted-acidic ionic liquid 1-methyl-3-(4-sulfobutyl)imidazolium triflate [BMIM(SO3H)][OTf] was demonstrated to act efficiently as solvent and catalyst for the halogenation of activated organic compounds with N-halosuccinimides (NXS) under mild conditions with short reaction times. Methyl aryl ketones were converted into α-halo and α,α-dihaloketones, depending on the quantity of NXS used. Ketones with activated aromatic rings were selectively halogenated, however in some cases mixtures of α-halogenated ketone and ring-halogenated ketones were obtained. Activated aromatics were regioselectively ring halogenated to give mono- and dihalo-substituted products. The [BMIM(SO3H)][OTf] ionic liquid (IL-A) was successfully reused eight times in a representative monohalogenation reaction with no noticeable decrease in efficiency. An effective halogenation scale-up in this IL is also presented. The reactivity trend and the observed chemo- and regioselectiivities point to an ET process in these IL-promoted halofunctionalization reactions.
Keywords: Brønsted-acidic ionic liquid; halogenation; aromatic ketones; NXS reagents; green chemistry
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Vražič, D.; Jereb, M.; Laali, K.K.; Stavber, S. Brønsted Acidic Ionic Liquid Accelerated Halogenation of Organic Compounds with N-Halosuccinimides (NXS). Molecules 2013, 18, 74-96.
Vražič D, Jereb M, Laali KK, Stavber S. Brønsted Acidic Ionic Liquid Accelerated Halogenation of Organic Compounds with N-Halosuccinimides (NXS). Molecules. 2013; 18(1):74-96.
Vražič, Dejan; Jereb, Marjan; Laali, Kenneth K.; Stavber, Stojan. 2013. "Brønsted Acidic Ionic Liquid Accelerated Halogenation of Organic Compounds with N-Halosuccinimides (NXS)." Molecules 18, no. 1: 74-96.