Journal
TETRAHEDRON LETTERS
Volume 53, Issue 50, Pages 6782-6785Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tetlet.2012.09.137
Keywords
Arene nitration; Bismuth nitrate; Imidazolium ionic liquids; Comparative reactivity; Isomer distribution; ipso Substitution
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Funding
- UNF
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A suspension of bismuth nitrate pentahydrate (BN) in [bmim][PF6] or [bmim][BF4] imidazolium ionic liquid (IL) is an effective reagent for ring nitration of activated aromatics under mild conditions without the need for external promoters. Nitration can also be effected in 1,2-DCE, MeCN, or MeNO2 without additives. Nitration of activated arenes (anisole, toluene, ethylbenzene, cumene, p-xylene, mesitylene, durene, and 1,3-dimethoxybenzene) is considerably faster (time to completion) in BN/[bmim][PF6] relative to BN/ 1,2-DCE and there are also differences in isomer distributions (for anisole, toluene, and ethylbenzene). With introduction of strongly deactivating substituents (-CHO; -MeCO; -NO2) the BN/IL system is no longer active but reactions still proceed with BN/1,2-DCE in reasonable yields. The ready availability and low cost of BN, simple operation, and absence of promoters, coupled to recycling and reuse of the IL, provide an attractive alternative to classical nitration methods for activated arenes. Switching from Bi(NO3)(3)center dot 5H(2)O/[bmim][PF6] to Bi(NO3)(3)center dot 5H(2)O/1,2-DCE increases the scope of the substrates that can be nitrated. (C) 2012 Elsevier Ltd. All rights reserved.
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