Full Paper
+
(
electrospray, 20 V): m/z=1281.6 [MÀAuÀC H +H] , 492.5
Conclusion
8
5
2
+
[MÀ2AuÀ2C H +2H]
;
elemental analysis calcd (%) for
C H N Au (H O) : C 51.3, H 4.93, N 5.2; found: C 51.4, H 5.25, N
8
5
We have obtained and fully characterized two NHC–gold–ace-
tylide MOMPs based on our recently described triphenylene-
tris-NHC ligand. The new solids were tested in the catalytic re-
69 75
6
3
2
2
5
.05.
General procedure for the reduction of nitroarenes in aque-
ous medium
duction of nitroarenes with NaBH and in the three-component
4
Strecker reaction for the synthesis of a-aminonitriles, and
showed high activity in both processes. Whereas their activity
in the reduction of nitroarenes can be attributed to the forma-
Nitroarene (1.078 mmol) and sodium borohydride (50 mmol) were
placed in a Schlenk tube, which was evacuated and filled with ni-
trogen three times. The solids were stirred in 10 mL of Mili-Q
water/MeOH (1/1) under a nitrogen steam for 15 min. Then, solid 2
or 3 (2.5 mg containing 5.1ꢁ10 mmol of gold, 0.5 mmol%) was
added. The resulting mixture was stirred at room temperature for
tion of Au nanoparticles due to the use of NaBH as reducing
4
agent, the activity in the Strecker reaction may originate from
Lewis acidic activation of the ketone or imine on coordination
to Au. We believe that this is the first time that a gold catalyst
has been used in the Strecker reaction, and therefore the re-
sults described here represent a new application of gold in
a heterogeneously catalyzed reaction.
À3
5
h. The solid residue was separated by filtration and washed with
distilled water and acetone. The filtrate was extracted with ethyl
acetate (3ꢁ10 mL) and the extract dried over MgSO . The solvent
was evaporated under vacuum. Yields were determined by H NMR
4
1
spectroscopy with 1,3,5-trimethoxybenzene (1.078 mmol) as inter-
nal standard.
Experimental Section
General procedure for the synthesis of a-aminonitriles
Synthesis of 2
(
Strecker reaction)
NaOH (40.6 mg, 0.51 mmol) and 1,4-diethynylbenzene (7.13 mg,
A capped vessel containing a stirrer was charged with the corre-
sponding ketone (0.5 mmol), aniline (0.55 mmol), TMSCN (1 mmol),
anisole as internal reference (0.5 mmol), the catalyst (0.02 mmol
Au), and 2 mL of dichloromethane. The resulting mixture was
stirred for 12 h at room temperature. For recycle tests, the catalyst
was recovered by centrifugation and washed with dichlorome-
thane. The evolution of the reactions and yields were determined
by GC analysis.
0
.054 mmol) were dissolved in 20 mL of methanol. This mixture
was heated to reflux for 15 min and then compound 1 (50 mg,
.036 mmol) was added as a solid. The resulting suspension was
0
heated to reflux for 4 h. The resulting brown solid was collected by
filtration and washed with water, methanol, acetonitrile, dichloro-
methane, toluene, hexane, and diethyl ether. Yield: 35 mg (68%);
À1
IR (ATR): n˜ (CꢀC)=2102 cm ; elemental analysis calcd (%) for
(
C H N Au ) : C 49.29, H, 4.55, N 5.75; found: C 48.95, H, 4.60, N
60 66 6 3 n
5
.39.
Acknowledgements
Synthesis of 3
NaOH (31.7 mg, 0.76 mmol) and 1,3,5-triethynylbenzene (5.43 mg,
We gratefully acknowledge financial support from Ministerio
de Economia y Competitividad of Spain (CTQ2011-24055/BQU)
and UJI (P1.1B2011-22). We would also like to thank the
Ramꢂn y Cajal program (M.P.). Sergio Gonell thanks the Minis-
terio de Ciencia e Innovaciꢂn for a fellowship. The authors are
grateful to the Serveis Centrals d’Instrumentaciꢂ Cientꢃfica
(SCIC) of the Universitat Jaume I for providing us with all char-
acterization techniques. We are very grateful to Dr. Brunklaus
0
.036 mmol) were dissolved in 20 mL of methanol. This mixture
was heated to reflux for 15 min and then compound 1 (50 mg,
.036 mmol) was added as a solid. The resulting suspension was
0
heated to reflux for 4 h. The resulting yellow solid was collected by
filtration and washed with water, methanol, acetonitrile, dichloro-
methane, toluene, hexane, and diethyl ether. Yield: 46.6 mg (90%);
À1
IR (ATR): n˜ (CꢀC): 2103 cm ; elemental analysis calcd (%) for
(
C H N Au ) : C 48.11, H 4.46, N 5.91; found: C 47.75, H 4.56, N
57 63 6 3 n
13
5
.56.
for the C (CP/MAS) NMR spectra of this work. We also thank
Francisco Gonell for helpful comments.
Synthesis of 4
NaOH (31.7 mg, 0.76 mmol) and phenylacetylene (17.6 mL,
Keywords: carbene ligands · coordination polymers · gold ·
heterogeneous catalysis · Strecker reaction
0
.108 mmol) were dissolved in 20 mL of methanol. This mixture
was heated to reflux for 15 min and then compound 1 (50 mg,
.036 mmol) was added as a solid. The resulting suspension was
0
[
1] J. C. Bailar, Jr., Prep. Inorg. React. 1964, 1, 1–27.
heated to reflux for 4 h. A white solid formed. The volatile materi-
als were evaporated. The resulting solid was dissolved in dichloro-
methane, filtered through a pad of Celite, and the solvent removed
under vacuum. Precipitation from CH Cl /hexane gave the desired
2004, 73, 3–14; c) K. Rurarek, R. Martꢃnez-MꢄÇez, The Supramolecular
Chemistry of Organic-Inorganic Hybrid Materials, John Wiley & Sons,
2
2
1
product as a white solid. Yield: 77 mg (91%); H NMR (500 MHz,
3
CDCl ): d=9.01 (s, 6H, CH ), 7.52 (d, J =8.3 Hz, 6H, CHarom),
3
arom
HH
3
3
7
2
.23 (t, J =7.4 Hz, 6H, CH ), 7.17 (d, J =7.4 Hz, 3H, CHarom),
HH arom HÀH
13
.39 ppm (s, 54H, C(CH ) ); C NMR (126 MHz, CDCl ): d=199.6
3
3
3
(
AuCcarbene), 134.7 (Cq arom), 132.4 (CHarom acetylide), 127.9 (CHarom acetylide),
1
1
26.4 (CHarom acetylide), 126.0 (Cq acetylide), 125.5 (Cq arom), 121.8 (Cq acetylide),
09.3 (CHarom), 106.7 (Cq acetylide), 62.6 (C(CH ) , 33.5 ppm (C(CH ) ; MS
3 3
3 3
Chem. Eur. J. 2014, 20, 1 – 7
5
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&
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