10.1002/cssc.201802359
ChemSusChem
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2 mL). The organic layers were dried with sodium sulfate and evaporated
under reduced pressure.
Figure 4. Representative TEM images at different magnifications of Au@SBA15 after seven runs in EtOH abs. under flow conditions.
Typical procedure for a sustainable protocol for the preparation of 2a
under batch conditions
Acknowledgements
In a vial of 10 mL, 2%Au@SBA15 catalyst (100 mg, 2 mol %), 4-
This project has received funding from the European Union’s
Horizon 2020 research and innovation programme under the
Marie Skłodowska-Curie grant agreement No 721290. This
publication reflects only the author’s view, exempting the
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nitroanisole 1a (76.5 mg, 0.5 mmol), NaBH4 (114 mg, 6 eq), and EtOH abs.
(9 mL) were placed. The reaction mixture was stirred at 30 °C for 2 h. After
completion, the solid catalyst was separated by centrifugation and then
washed with EtOH (2 x 2 mL), dried at 180 °C for 20 h and reused in a
successive cycle. After removal and recovery of the solvent via distillation
(90% of solvent recovered) the product was separated simple by washing
the residue with cyclopenthyl methyl ether (3 x 3 mL). The solvent was
evaporated by distillation (95% of solvent recovered) obtaining the pure
product (yield of 2a 95%).
Keywords: Heterogeneous catalysis • SBA-15 • Reduction of
nitroarenes • gold NP • flow conditions
E-factor calculation for product 2a (yield 95%): E-factor = [0.0765 g (4-
nitroanisolo, 1a) + 0.114 g (NaBH4) + 0.100 g (Au@SBA15) + 10.4 g
(EtOH) + 7.7 g (CPME) – 0.058 g (4-methoxyaniline, 2a) – 0.095 g
(recovered Au@SBA15) – 9.5 g (recovered EtOH) – 7.4 g (recovered
CPME)] / 0.058 g (4-methoxyaniline, 2a) = 23.1.
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Without recover of reaction medium the E-factor value was 314.4.
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Typical procedure for a sustainable protocol for the preparation of 2a
under flow conditions
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A premixed mixture of 1a (1.53 g, 10 mmol), NaBH4 (1.13 g, 3 eq) and and
EtOH abs. (40 mL)) was charged into a glass column functioning as a
reservoir. The equipment was connected, by using the appropriate valves,
to a pump and installed into a box thermostated at 30 °C. The reaction
mixture was continuously pumped (flow rate: 0.1 mL∙min-1; residence
time: 50 min) through the catalyst column (15 cm, stainless steel HPLC
column) equipped with a 120 psi back pressure regulator, and the reaction
was monitored by GC. Product was collected in fractions and gold content
in the EtOH solution was periodically measured by MP-AES analysis. After
completion 40 mL of EtOH was used to wash the catalyst inside the reactor.
After removal and recovery of the solvent via distillation (90% of solvent
recovered) the product was separated simple by washing the residue with
cyclopenthyl methyl ether (3 x 20 mL). The solvent was evaporated by
distillation (95% of solvent recovered) obtaining the pure product (yield of
2a 97%).
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E-factor calculation for product 2a (yield 97%): E-factor = [1.53 g (4-
nitroanisole, 1a) + 1.13 g (NaBH4) + 64 g (EtOH) + 52 g (CPME) – 1.19 g
(4-methoxyaniline, 2a) – 58 g (recovered EtOH)] – 50 g (recovered CPME)]
/ 1.19 g (4-methoxyaniline, 2a) = 7.96.
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