European Journal of Organic Chemistry
10.1002/ejoc.201700990
FULL PAPER
Conclusions
collection was based on three ω-scan runs (starting = -34º) at values of φ
=
0º, 120º, and 240º with the detector at 2θ = -32º. For each of the runs,
6
06 frames were collected at 0.3º intervals and 10 s per frame. An
To conclude, this study has expanded the use of heterogeneous
catalysts based on alkaline earth metals (such as calcium and
barium). The preparation of a variety of heterogeneous catalysts
based on calcium and barium was achieved by means of a
straightforward and easy to carry out procedure. This study also
showed that small variations in the metal-organic framework
precursors, such as the counterion of the organic linker,
provided different pattern in the final structure, what can
influence in the catalytic activity of the heterogeneous catalyst.
The set of prepared catalysts is a toolkit to mediate in synthetic
processes, such as the synthesis of quinoline via Friedländer
reaction. The catalytic systems presented allow the reaction
additional run at φ=0º of 100 frames was collected to improve
redundancy. The diffraction frames were integrated using the program
SAINT, and the integrated intensities were corrected for
Lorentz_polarization effects and absorption with SADABS. The structure
was solved by direct methods and refined to all 2366 unique Fo
matrix least-squares calculations using SHELXL-97. All the hydrogen
atoms, except the hydrogens of the H O molecules, were placed at
idealized positions and refined using a riding model. The positions of the
water hydrogens are located in the Fourier difference map and refined
using a riding model. Final R1 indices [1852 with I>2σ(I)] 0.0527, wR2 =
2
by full
2
0
1
.1163. R indices (all data) R1 = 0.0713, wR2 = 0.1246. S[F2] 1.095 for
54 refined parameters. Crystal data: C14H22CaN4O12, M = 478.44,
monoclinic, a =4.8879(6) Å, b = 29.526(4) Å, c = 7.1117(12) Å, α = γ =
90º, 93.693(2)º, 1024.2(2) crystal dimensions:
0.32x0.22x0.08 mm, space group: P 21/n, Z = 2, F(000) = 500, μ = 0.377
between
carbonyl
compounds
and
not
only
2-
β
=
V
=
Å ,
3
aminobenzophenones but also 2-aminobenzaldehydes, which
have not previously been reacted in the presence of metal-
organic frameworks for quinoline synthesis. Both, conventional
heating or microwave heating can be employed with similar
-
1
mm .
results in this transformation, although longer reaction times are Acknowledgements
needed for the former. Furthermore, the reusability of this type of
catalysts have been proved, the material bcmim-Ba1 being the
most robust among the considered in this study.
The Spanish Ministry (Ministerio de Economía y Competitividad,
CTQ2015-66624-P) and the University of Alicante (VIGROB-
285) are gratefully acknowledged for financial support. M.A.S.
thanks the Spanish Ministry (Ministerio de Educación, Cultura y
Deporte, FPU15/06040) for a Predoctoral Fellowship.
Experimental Section
General. All reagents and solvents were used as supplied commercially.
Analytical thin-layer chromatography (TLC) was performed on 0.2 mm
coated Science silica gel (EM 60-F254) plates purchased from Merck,
Germany. Visualization was achieved by UV light (254 nm). Flash
Keywords: alkaline earth • imidazole • heterogeneous catalyst •
quinoline • metal-organic framework
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0
.25mm (inner diameter) and 0.25 μm (film).
(
pp. 1189-1216.
General procedure for the synthesis of quinolines. A mixture of the
corresponding 2-aminobenzaldehyde (see Supporting Information) or 2-
aminoarylketone and ketone (2, 5 or 10 equivalents) was stirred at 80 ºC
in the presence of the corresponding catalyst (10 mol-% metal)
employing microwaves as the heating source (initial power 80 W) or
conventional heating. After cooling down the mixture, it was filtered
through celite to remove the catalyst, eluting with ethyl acetate. The
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Structural analysis of bcmim-Ca2.[27] X-ray diffraction data were
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a Bruker Smart CCD diffractometer with graphite
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