pubs.acs.org/joc
hydrochloric acid,2a microwave techniques (900 W) in
Ambiphilic Dual Activation Role of a Task-Specific
Ionic Liquid: 2-Hydroxyethylammonium Formate
as a Recyclable Promoter and Medium for the
Green Synthesis of β-Nitrostyrenes
ammonium acetate,2b ultrasound (US)/NH4OAc/HOAc,2c
direct nitration of alkenes with copper(II) tetrafluoroborate
and NaNO2 in acetonitrile,2d Clayfen by MW irradiation
(100-110 °C),2e and ceric ammonium nitrate (CAN)2f have
been utilized to obtain nitroalkenes. In addition, various
heterogeneous catalysts such as zeolite,3a aminopropyl-functio-
nalized silicas (APS),3b FDU-ED (diamino-functionalized
mesostructured polymers),3c and MCM-41 silica3d have been
employed for the synthesis of nitroalkenes starting from
aromatic aldehydes and nitroalkanes. However, most of
the reported methods have one or more of the following
drawbacks: for example, use of expensive reagents and
volatile organic solvents, long reaction times, low yields of
products, complicated reaction assembly, and tedious work-
up, etc.
Abdolhamid Alizadeh,* Mohammad M. Khodaei,* and
Ali Eshghi
Department of Chemistry and Nanoscience & Nanotechnology
Research Center (NNRC) Razi University,
Kermanshah 67149, Iran
ahalizadeh2@hotmail.com; mmkhoda@razi.ac.ir
Received August 28, 2010
In view of the projected benefits of ionic liquids (ILs) for
organic transformations for sustainable development such
as environmental compatibility, reusability, greater selectivity,
operational simplicity, noncorrosiveness, and ease of isolation,4
we were attracted toward the use of ILs. A survey of the
literature indicated that there is no report aimed at the synthe-
sizing of β-nitrostyrenes utilizing ionic liquids. Herein, we report
the first utilization of a low cost and task-specific ionic liquid,
namely 2-hydroxyethylammonium formate (2-HEAF),5 in de-
veloping an environmentally improved route to β-nitrostyrene
derivatives.
To examine the effect of 2-HEAF as an ionic liquid, the
reaction of nitromethane with benzaldehyde under neat
condition and at room temperature was considered for
a model study. An initial screening was done to obtain
maximum conversion to the product in the shortest period.
The progress of the reactions was monitored by TLC taking
into consideration the complete consumption of aldehyde.
The reactants (1 mmol of benzaldehyde and 1 mmol of
nitromethane) were obtained unchanged even after 48 h
stirring in ethanol without addition of 2-HEAF at rt and
also under reflux conditions (Table 1, entries 1 and 2). The
lack of formation of any significant amount of the desired
product without using the IL indicated the specific role of
2-HEAF in imparting the catalytic property. To optimize the
quantity of IL required, the reaction was carried out in the
presence of 1, 0.5, and 5 mL of 2-HEAF under neat condi-
tions and room temperature. In these cases, the desired
A cost-effective task-specific ionic liquid, 2-hydroxyethyl
ammonium formate, efficiently promotes the condensa-
tion of nitroalkanes with various aldehydes to produce
β-nitrostyrenes in high to excellent yields at room tem-
perature. This reaction does not involve any hazardous
organic solvent and toxic catalyst. The ionic liquid is
recovered and recycled for subsequent reactions. In addi-
tion, a novel mechanism has been proposed invoking
ambiphilic dual activation influence of the ionic liquid.
As the nitro group is a strong electron-withdrawing group,
nitroalkenes are versatile synthetic reagents. For example,
conjugate addition,1a Diels-Alder reaction,1b and 1,3-dipo-
lar addition1c using nitroalkenes are powerful methods for
carbon-carbon bond formation. Moreover, since after these
reactions the nitro groups can be converted into various
functional groups, nitroalkenes have become important
intermediates in organic synthesis, and several strategies
for their synthesis are known. Henry reaction (condensation
of carbonyl compounds with nitroalkanes followed by
β-elimination of the resulting 2-nitro alcohols) is one of the
well-, alcoholic sodium hydroxide solution and concentrated
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Rao, M.; Rao, S.; Srinivas, P.; Suresh Babu, K. Tetrahedron Lett. 2005, 46,
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(3) (a) Ballini, R.; Bigi, F.; Gogni, E.; Maggi, R.; Sartori, G. J. Catal.
2000, 191, 348. (b) Sartori, G.; Bigi, F.; Maggi, R.; Sartorio, R.; Macquarrie,
D. J.; Lenarda, M.; Storaro, L.; Coluccia, S.; Martra, G. J. Catal. 2004, 222,
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(4) Wasserscheid, P.; Welton, T. Ionic Liquid in Synthesis; Wiley-VCH:
Weinheim, 2004.
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DOI: 10.1021/jo101696z
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Published on Web 11/03/2010
J. Org. Chem. 2010, 75, 8295–8298 8295
2010 American Chemical Society