The first example of electrophilic substitution on a benzannulene

Mitchell, Reginald H.; Yan, Joseph Shue-Hen

doi:10.1016/s0040-4039(01)86127-x

Cited by 2 publications

(1 citation statement)

References 12 publications

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“…(a) In [emim][NO 3 ]. The Cu(II)nitrate/acetic anhydride system has been used for nitration of activated systems such as annulenes and cyclophanes . Using Cu(II)nitrate/TFAA in the present study, we find that toluene is nitrated in [emim][NO 3 ] ionic liquid solvent in reasonable yield (59% isolated yield; ortho / para ratio = 0.92).…”

Section: Resultssupporting

confidence: 67%

Electrophilic Nitration of Aromatics in Ionic Liquid Solvents

2000

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Potential utility of a series of 1-ethyl-3-methylimidazolium salts [emim][X] with X = OTf-, CF3COO-, and NO3- as well as [HNEtPri2][CF3COO] (protonated Hünig's base) ionic liquids were explored as solvent for electrophilic nitration of aromatics using a variety of nitrating systems, namely NH4NO3/TFAA, isoamyl nitrate/BF3.Et2O, isoamyl nitrate/TfOH, Cu(NO3)/TFAA, and AgNO3/Tf2O. Among these, NH4NO3/TFAA (with [emim][CF3COO], [emim][NO3]) and isoamyl nitrate/BF3.Et2O, isoamyl nitrate/TfOH (with [emim][OTf]) provided the best overall systems both in terms of nitration efficiency and recycling/reuse of the ionic liquids. For [NO2][BF4] nitration, the commonly used ionic liquids [emim][AlCl4] and [emim][Al2Cl7] are unsuitable, as counterion exchange and arene nitration compete. [Emim][BF4] is ring nitrated with [NO2][BF4] producing [NO2-emim][BF4] salt, which is of limited utility due to its increased viscosity. Nitration in ionic liquids is surveyed using a host of aromatic substrates with varied reactivities. The preparative scope of the ionic liquids was also extended. Counterion dependency of the NMR spectra of the [emim][X] liquids can be used to gauge counterion exchange (metathesis) during nitration. Ionic liquid nitration is a useful alternative to classical nitration routes due to easier product isolation and recovery of the ionic liquid solvent, and because it avoids problems associated with neutralization of large quantities of strong acid.

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Section: Resultssupporting

confidence: 67%