Chlorination of Aromatics with Trichloroisocyanuric Acid (TCICA) in Brønsted-Acidic Imidazolium Ionic Liquid [BMIM(SO3H)][OTf]: an Economical, Green Protocol for the Synthesis of Chloroarenes*
Abigail Hubbard A , Takao Okazaki A and Kenneth K. Laali A BA Department of Chemistry, Kent State University, Kent, OH 44242, USA.
B Corresponding author. Email: klaali@kent.edu
Australian Journal of Chemistry 60(12) 923-927 https://doi.org/10.1071/CH07261
Submitted: 26 July 2007 Accepted: 2 October 2007 Published: 4 December 2007
Abstract
A survey study on electrophilic chlorination of aromatics with trichloroisocyanuric acid (TCICA) in Brønsted-acidic imidazolium ionic liquid [BMIM(SO3H)][OTf] is reported. The reactions are performed under very mild conditions (at ~50°C) and give good to excellent yields, depending on the substrates. Chemoselectivity for mono- v. dichlorination can be tuned by changing the arene-to-TCICA ratio and the reaction time. The survey study and competitive experiments suggest that triprotonated/protosolvated TCICA is a selective/moderately reactive transfer-chlorination electrophile. Density functional theory was used as guide to obtain further insight into the nature of the chlorination electrophile and the transfer-chlorination step.
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* Part of undergraduate Honours Thesis of Abigail Hubbard: Halogen Introduction Strategies through Onium Ion Chemistry in Ionic Liquid Solvents (Kent State University) May 2007.