Eleni Vasilikogiannaki et al.
COMMUNICATIONS
NPs does not involve H as a reducing agent, but
Synth. Catal. 2011, 353, 1260–1264; f) V. Pandarus, R.
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2
rather highly reactive gold hydride species (transfer
hydrogenation). The fate of ammonia·borane after re-
duction is still unknown and currently under examina-
tion.
In conclusion, we have presented the first practical
protocol regarding the gold-catalysed activation of
a boron hydride substance towards the reduction of
nitro compounds, in contrast to previous examples
2
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9
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4
efficiency of Au NPs, operating even at ppm level, ex-
[
9]
emplifies once more their unique nature in catalysis.
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To a vial containing para-nitrotoluene (1.0 g, 7.3 mmol) and
5 mL ethanol were added at room temperature NH -BH
1
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3
3
(
(
336 mg, 10.9 mmol) and immediately after Au/TiO2
145 mg, 0.1 mol%) in two portions. For large-scale experi-
ments, such as this one, ice bath cooling is necessary since
the reaction is exothermic. Additionally, to avoid the forma-
tion of minor side-products (e.g., azoxyarene), inert atmos-
phere conditions are preferable. The reaction was monitored
by TLC, and after 30 min, the slurry was filtered under pres-
sure through a short pad of celite or preferably silica gel to
withhold the supported catalyst and inorganic salts with the
aid of ethanol or methanol (10 mL). The filtrate was evapo-
rated under vacuum to afford pure p-toluidine as a pale
yellow solid; yield: 0.75 g (96%).
Caution: Ammonia·borane complex is a stable substance
under normal conditions, however, it may decompose violent-
ly upon heating, especially over 1008C. It must be stored in
a dry, cool and well-ventilated place. It is advised to maintain
the temperature of reactions below 508C.
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Acknowledgements
2
This work was supported in part by the project “IRAKLEI-
TOS II - University of Crete” of the Operational Programme
for Education and Lifelong Learning 2007–2013
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ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2013, 355, 907 – 911