VIETNAM NATIONAL UNIVERSITY – HO CHI MINH CITY
HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY
DANG HUYNH GIAO
Cu-BASED ORGANIC FRAMEWORKS AS CATALYSTS
FOR C–C AND C–N COUPLING REACTIONS
Major:
Organic Chemical Technology
Major code: 62527505
PhD THESIS SUMMARY
HO CHI MINH CITY 2015
The thesis was completed in University of Technology –VNU-HCM
Advisor 1:
Advisor 2:
Prof. Dr. Phan Thanh Son Nam
Dr. Le Thanh Dung
Independent examiner 1: Prof. Dr. Dinh Thi Ngo
Independent examiner 2: Assoc. Prof. Dr. Nguyen Thi Phuong Phong
Examiner 1: Assoc. Prof. Dr. Nguyen Cuu Khoa
Examiner 2: Assoc. Prof. Dr. Nguyen Thai Hoang
Examiner 3: Assoc. Prof. Dr. Le Thi Hong Nhan
The thesis will be defended before thesis committee at
.....................................................................................................................
.....................................................................................................................
On………………………………………………………………………………..
The thesis information can be looked at following libraries:
- General Science Library Tp. HCM
- Library of University of Technology – VNU-HCM
Abstract
Four highly porous Copper-based organic frameworks (Cu-MOFs) such
as Cu3 (BTC)2 , Cu2 (BDC)2 (DABCO), Cu2 (BPDC)2 (BPY) and Cu(BDC) were
synthesized and characterized by X-ray powder diffraction (PXRD), scanning
electron microscopy (SEM), transmission electron microscopy (TEM),
thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy
(FT-IR), inductively coupled plasma mass spectrometry (ICP-MS), hydrogen
temperature-programmed reduction (H2 -TPR) and nitrogen physisorption
measurements. Three Cu-MOFs including Cu3 (BTC)2 , Cu2 (BDC)2 (DABCO),
Cu2 (BPDC)2 (BPY) were used as heterogeneous catalysts for direct CC
coupling reactions to synthesize propargylamines. Cu(BDC) was employed as
heterogeneous catalyst for CN coupling reaction to synthesize quinoxalines.
These catalytic systems offered practical approaches with high yields and
selectivity. Additionally, broad functionality was shown to be compatible. The
Cu-MOFs catalysts could be recovered and reused several times without
significant degradation in catalytic activity. To the best of our knowledge, these
transformations using Cu-MOFs catalysts were not previously mentioned in the
literature.
INTRODUCTION
Homogeneous transition metals are often employed as catalysts to
promote the transformation of an organic compound in the liquid phase.
However, difficulties in removing catalyst impurities in the final products
narrow the application of homogeneous catalytic systems, especially in
pharmaceutical industry. Metal-organic frameworks (MOFs) have recently
attracted significant attention with advantages in replacing homogeneous
catalysts in chemical process.
Propargylamines
and
quinoxalines
have
emerged
as
important
intermediates in the synthesis of numerous nitrogen-containing biologically
active compounds as well as a variety of functional organic materials. Many
transition-metal catalytic systems, both in homogeneous and heterogeneous
catalysis, were applied for the preparation of propargylmines and quinoxalines
via the C−C and C−N coupling reations. However, many of those processes
suffered from one or more limitations such as harsh reaction conditions, low
product yields, tedious work-up procedures, and the use of toxic metal salts as
catalysts. Consequently, study for the high-effective, sustainable synthetic
routes of proparylamines and quinoxalines is an unquestionable trend in near
future.
Among several popular MOFs, copper-based organic frameworks (CuMOFs) previously exhibited high activity in various organic reactions due to
their unsaturated open copper metal sites. Especially, the Cu-MOFs including
Cu3 (BTC)2 , Cu(BDC), Cu2 (BDC)2 (DABCO) and Cu2 (BPDC)2 (BPY), which are
constructed from copper salts and 1,4-benzenedicarboxylic acid (BDC), 1,3,5benzenetricarboxylic acid (BTC) and 4,4’-biphenyldicarboxylic acid (BPDC),
exhibit many advantages for catalytic application. Those organic linkers are
commercial and relatively cheap. These Cu-MOFs have surface areas higher
than 1000 m2 /g (except for Cu(BDC)) and thermal stability of up to 300 °C or
higher. Moreover, the largest pore apertures of Cu2 (BDC)2 (DABCO),
Cu3 (BTC)2 and Cu2 (BPDC)2 (BPY) are in the range of 7.5 – 9.0 Å which can
allow average size substrates to enter the pores and reach catalytic sites.
However, to the best of our knowledge, the direct C–C and C–N coupling
reactions for the synthesis of proparylamines and quinoxalines using these CuMOFs were not previously mentioned in the literature.
The first purpose of this thesis is to synthesize Cu-MOFs including
Cu3 (BTC)2 , Cu(BDC), Cu2 (BDC)2 (DABCO) and Cu2 (BPDC)2 (BPY). The
second objective is to study their use as heterogeneous catalysts for the direct
C–C and C–N coupling reactions to form proparylamines and quinoxalines.
CHAPTER 1
LITERATURE REVIEW: Cu3 (BTC)2 ,
Cu2 (BDC)2 (DABCO), Cu2 (BPDC)2 (BPY), Cu(BDC) AND C–C, C–N
COUPLING REACTIONS
1.1 Introduction to metal-organic frameworks
In comparison with other porous materials, MOFs possess unique
structures, in which the metal ions combine with organic linkers
to form secondary building units (SBUs), which dictate the
final topology of a whole framework. The combination of
numerous kinds of linkers and metal ions can lead to considerable
diversity of this material.
Many studies reported MOFs containing copper active sites as efficient
heterogeneous catalysts.
Among organic linkers that are often used for Cu-MOFs synthesis, 1,4benzenedicarboxylic
acid (BDC), 1,3,5-benzenetricarboxylic
acid
(BTC) and 4,4’-biphenyldicarboxylic acid (BPDC) have advantages
that they are commercial and relatively cheap. In another approach,
MOFs can be constructed from mixed linkers to provide greater
flexibility in terms of surface area, modifiable pore size and chemical
environment. Linkers BDC and BPDC could be easily combined with
pillar linkers such as 1,4-diazabicyclo [2.2.2]octane (DABCO) or 4,4’bipyridine (BPY) to form rigid Cu-MOFs. Therefore, Cu-MOFs
constructed from BDC, BTC or BPDC recently attracted great
attention.
1.1
1.2 Cu3 (BTC)2, Cu(BDC), Cu2 (BDC)2(DABCO) and
Cu2 (BPDC)2 (BPY)
Cu3 (BTC)2 , Cu(BDC), Cu2 (BDC)2 (DABCO) and Cu2 (BPDC)2 (BPY)
constitute Cu-MOFs that contain common SBUs of two 5-coordinate
copper cations bridged in a paddle wheel-type configuration (Fig. 1.4).
Fig 1.4. Common coordination geometry of paddle wheel building units of
Cu3 (BTC)2 , Cu2 (BDC)2 (DABCO), Cu2 (BPDC)2 (BPY), Cu(BDC) and their
framework structures (L = Carboxylate linker, P = N-containing bidentate pillar
linker and G = Guest molecule).
Cu3 (BTC)2 , Cu(BDC), Cu2 (BDC)2 (DABCO) and Cu2 (BPDC)2 (BPY)
are synthesized by solvothermal methods. Their physicochemical
properties are presented in Table 1.2:
Table
1.2:
Physicochemical
properties
of
Cu3 (BTC)2 ,
Cu2 (BDC)2 (DABCO) and Cu2 (BPDC)2 (BPY)
MOFs
Decomposition BET surface
temperature
area
(°C)
(m2 /g)
Cu3 (BTC)2
300
1000-1450
Cu(BDC),
Pore
aperture (Å2 )
8.0 9.0
Cu(BDC)
325
545-625
_
Cu2 (BDC)2 (DABCO)
300
1461
7.5 7.5
4.7 3.8
Cu2 (BPDC)2 (BPY)
320
1210
12.3 7.8
8.8 8.0
Cu3 (BTC)2 , Cu(BDC), Cu2 (BDC)2 (DABCO) and Cu2 (BPDC)2 (BPY)
can be characterized by various techniques, such as single crystal X-ray
diffraction (SC-XRD), powder X-ray diffraction (PXRD), scanning
electron microscopy (SEM), Fourier transform infrared (FT-IR),
transmission electron microscopy (TEM), thermogravimetric analysis
(TGA), inductively coupled plasma mass spectrometry (ICP-MS), and
gas physisorption measurement, etc.
1.3 C–C coupling reactions
Traditional routes to access propargylamines often suffer from
disadvantages such as hard conditions, low yields, and limited reaction
scopes.
Difficults in removing catalysts contaminated in final products narrow
the application of homogeneous catalytic systems, especially in
pharmaceutical industry.
Recently, the most attractive synthetic route is the use of Manich-type
reaction, a three component procedure of terminal alkynes,
formaldehyde, and secondary amines. However, the aldehyde-free,
oxidative Manich reactions have not been previously reported under
any catalysis.
1.4 C–N coupling reactions
Traditionally, quinoxalines have been prepared by the acid-catalyzed
condensation of 1,2-aryldiamines with 1,2-diketone or 1,2-diketone
alternatives, such as epoxides, α-bromoketones, and α-hydroxyketones.
Although the contamination of the desired products with transition
metals or other solids would be minimized under heterogeneous
catalysts conditions, developing an efficient heterogeneous catalyst
system for the quinoxaline synthesis still remains to be explored.
1.2
1.5 Aim and objectives
Propargylamines and quinoxalines are frequently found as the versatile
intermediates for the synthesis of many nitrogen-containing
biologically active compounds.
Cu3 (BTC)2 , Cu2 (BDC)2 (DABCO), Cu2 (BPDC)2 (BPY) and Cu(BDC)
have many advantages for suitable catalytic applications.
To the best of our knowledge, the direct C–C and C–N coupling
reactions for synthesizing proparylamines and quinoxalines using these
Cu-MOFs were not previously mentioned in the literature.
The
main
aim
of
this
dissertation
is
using
Cu3 (BTC)2 ,
Cu2 (BDC)2 (DABCO), Cu2 (BPDC)2 (BPY) and Cu(BDC) as catalysts
for the synthesis of proparylamines and quinoxalines:
i) Synthesis and characterization of the Cu-MOFs including
Cu3 (BTC)2 , Cu2 (BDC)2 (DABCO), Cu2 (BPDC)2 (BPY) and Cu(BDC);
ii)Catalytic
studies
of
Cu3 (BTC)2 ,
Cu2 (BDC)2 (DABCO),
Cu2 (BPDC)2 (BPY) on C–C coupling reactions between amine
compounds and terminal alkynes, catalytic studies of Cu(BDC) on C–N
coupling reaction between α-hydroxyacetophenone and ophenylenediamine.
CHAPTER 2 SYNTHESIS AND CHARACTERIZATION OF
Cu3 (BTC)2 , Cu2 (BDC)2(DABCO), Cu2 (BPDC)2 (BPY), Cu(BDC)
2.1 Introduction
In this chapter, the synthesis, characterization methods, physicochemical
properties of Cu3 (BTC)2 , Cu2 (BDC)2 (DABCO), Cu2 (BPDC)2 (BPY) and
Cu(BDC) were studied.
2.2 Experimental
Cu3 (BTC)2 , Cu2 (BDC)2 (DABCO), Cu2 (BPDC)2 (BPY) and Cu(BDC)
were synthesized by solvothermal methods.
They were charactized by different techniques such as PXRD, FT-IR,
SEM, TEM, TGA, ICP-MS and nitrogen physisorption measurement.
2.3
Results and discussions
2.3.1
Synthesis and characterization of Cu3 (BTC)2
The synthesis yield was approximately 85% based on H3 BTC.
The copper content in the Cu3 (BTC)2 was 29% (ICP-MS).
The BET surface areas of Cu3 (BTC)2 were achieved approximately
1799 m2 /g, the Langmuir surface areas were achieved approximately
2007 m2 /g.
The thermal stability of Cu3 (BTC)2 is over 300 o C (TGA).
The PXRD pattern of the synthesized Cu3(BTC)2 was similar to the
simulated pattern previously reported in the literature (Figure 2.2).
The SEM micrograph indicated Cu3(BTC)2 exhibited a cubic octahedral
morphology (Fig. 2.4).
Figure 2.2 X-ray powder
diffractograms of the simulated
Cu3 (BTC)2 (a) and the synthesized
Cu3 (BTC)2 (b)
2.3.2
Figure 2.4 SEM micrograph
of the Cu3 (BTC)2
Synthesis and characterization of Cu2 (BDC)2 (DABCO)
The synthesis yield was approximately 66% based on H2 BDC.
The copper content in the Cu2 (BDC)2 (DABCO) was 21.5% (ICP-MS).
Langmuir surface areas of Cu2 (BDC)2 (DABCO) were achieved
approximately 1174 m2 /g.
The Cu2 (BDC)2 (DABCO) was stable up over 300 °C.
Figure 2.8 X-ray powder diffractograms of the
simulated Cu2 (BDC)2 (DABCO) (a) and the
synthesized Cu2 (BDC)2 (DABCO) (b)
Figure 2.9 SEM
micrograph of the
Cu2 (BDC)2 (DABCO)
The PXRD pattern of the synthesized Cu2 (BDC)2 (DABCO) was in
good accordance with the simulated pattern of the optimized plausible
structure by using Cerius 2 (Fig. 2.8).
Figure 2.9 showed that SEM micrograph of Cu2 (BDC)2 (DABCO)
revealed that well-shaped, high- quality cubic crystals were formed.
2.3.3 Synthesis and characterization of Cu 2 (BPDC)2 (BPY)
The synthesis yield was approximately 66% based on H2 BPDC.
The copper component in Cu2 (BPDC)2 (BPY) was 18% (ICP-MS).
Langmuir surface areas of 1519 m2 /g were achieved for the
Cu2 (BPDC)2 (BPY), BET surface areas were achieved 1082 m2 /g.
TGA result indicated that the Cu2 (BPDC)2 (BPY) was stable up to over
300 °C.
PXRD pattern of the Cu2 (BPDC)2 (BPY) (Fig. 2. 14) showed the
presence of a sharp peak at 2θ = 6°, being consistent with the simulated
pattern of single-crystal previously reported by James and co-workers.
The SEM micrograph of the Cu2 (BPDC)2 (BPY) revealed that the
formed crystals were well-shaped cubic (Fig 2.16).
Figure 2.14 X-ray powder diffractograms
of the simulated Cu2 (BPDC)2 (BPY) (a)
and the synthesized Cu2 (BPDC)2 (BPY) (b)
Figure 2.16 SEM micrograph
of the Cu2 (BPDC)2 (BPY)
2.3.4 Synthesis and characterization of Cu(BDC)
The synthesis yield was approximately 66% based on H2 BDC.
The copper content in the Cu(BDC) was 29% (ICP-MS).
Langmuir surface areas of 616 m2 /g were achieved for the material.
TGA result indicated that the Cu(BDC) was stable up to over 300 °C.
The PXRD pattern of the Cu(BDC) was also similar to the simulated
pattern previously reported in the literature (Fig. 2.20).
The
SEM micrograph indicated the
formation of the cubic
microcrystals of the Cu(BDC).
1.3
Figure 2.20 X-ray powder diffractograms of
the simulated Cu(BDC) (a) and the
synthesized Cu(BDC) (b)
Figure 2.22 SEM micrograph
of the Cu(BDC)
2.4 Conclusion
The four Cu-MOFs such as Cu3 (BTC)2 , Cu2 (BDC)2 (DABCO),
Cu2 (BPDC)2 (BPY) and Cu(BDC) were successfully synthesized and
characterized by PXRD, FT-IR, TGA, H2 TPR, ICP-MS and nitrogen
physisorption measurements.
CHAPTER 3
CATALYTIC STUDIES OF Cu3 (BTC)2 ,
Cu2 (BDC)2 (DABCO), Cu2 (BPDC)2 (BPY), Cu(BDC) ON C–C AND C–N
COUPLING REACTIONS
3.1 Introduction
Cu3 (BTC)2 , Cu2 (BDC)2 (DABCO), Cu2 (BPDC)2 (BPY) and Cu(BDC)
exhibited high activity for many reactions due to their unsaturated open
metal sites.
In
this
chapter,
the
catalytic
performance
of
Cu3 (BTC)2 ,
Cu2 (BDC)2 (DABCO), Cu2 (BPDC)2 (BPY) and Cu(BDC) on the C–C,
C–N coupling reactions will be discussed (Scheme 3. 1 and Scheme
3.2).
Scheme 3.1. The synthesis of propargylamines
Scheme 3.2. The synthesis of quinoxaline
1.4
3.2 Experimental
Catalytic studies of Cu3 (BTC)2 on C–C coupling reaction from N,Ndimethylanilines and terminal alkynes (reaction 1); Catalytic studies of
Cu2 (BDC)2 (DABCO) on C–C coupling reaction from N-methylanilines and
terminal alkynes (reaction 2); Catalytic studies of Cu2 (BPDC)2 (BPY) on C–C
coupling reaction from Tetrahydroisoquinoline, benzaldehydes and terminal
alkynes (reaction 3); Catalytic studies of Cu(BDC) on C–N coupling reaction
from α-hydroxyacetophenone and phenylenediamine (reaction 4).
The reaction conversions were monitored by withdrawing aliquots from the
reaction mixture at different time intervals, quenching with water (1 ml), drying
over anhydrous Na 2 SO4 , analyzing by Gas chromatographic (GC) with
reference to inernal standard. All major products from four reactions were
confirmed by 1 H NMR and 13 C NMR.
3.3 Results and discussions
3.3.1 Catalytic studies of Cu3 (BTC)2 on C–C coupling reaction (1)
Scheme 3.3. The direct oxidative C-C coupling reaction between N,Ndimethylaniline and phenylacetylene using Cu3 (BTC)2 as catalyst.
All optimized synthetic conditions of reaction 1 between N,Ndimethylaniline and phenylacetylene are summaried in Table 3.2.
Reaction conditions
Temperature
Results (Reaction conversion (%))
RT (0), 100 °C (56), 110 °C (76), 120 °C
(96)
Molar ratio of Phenylacetylene :
1:1 (85), 1: 2 (96), 1:3 (93)
N,N-dimethylaniline
Catalyst amount (%)
Oxidant
0 % (12), 1 % (65), 3 % (83), 5 % (96), 7
%(87)
TBHP (96), TBHP in decane (100),
DTBP (44), CHP (96, by product),
K2 S2 O8 and H2 O (no product)
1 (54), 1.5 (76), 2 (82), 3 (96)
DMA (96), Clorobenzene (45), o-xylene
(40), DMF, DEF, NMP (99, 95, 100,
byproduct)
Similar to Cu3 (BTC)2
No product appeared
Oxidant concentration (equiv)
Solvent
Other Cu-MOFs, Cu salts
Other MOFs
leaching test
100
80
80
Conversion (%)
Conversion (%)
5 mol%
100
60
40
60
40
20
20
0
0
0
25
50
75
100
Time (min)
125
1
150
Figure 3.9. Leaching test
indicated no contribution from
homogeneous catalysis of active
species leaching into reaction
solution
2
3
4
5
6
Run
7
8
9
10
Figure 3.12. Catalytic recycling studies
Leaching test indicated no contribution from homogeneous catalysis of
active species leaching into reaction solution (Fig. 3.9).
The Cu3 (BTC)2 catalyst could be recovered and reused ten times in the
direct C-C coupling reaction between N,N-dimethylaniline and
phenylacetylene without a significant degradation in catalytic activity.
Indeed, a conversion of 95% was still obtained after 150 min for the
transformation in the ten run (Fig. 3.12).
XRD result confirmed that the reused Cu3 (BTC)2 was still highly
crystalline. Moreover, FT-IR analysis of the reused Cu3 (BTC)2
exhibited a similar absorption as compared to that of the fresh CuMOF.
With various coupling starting materials of N,N-dimethylanilines and
terminal alkynes, all the products were characterized by 1 H NMR. The
yields were isolated yields. The results showed that the isolated yields
were achieved from 55% to 81%.
3.3.2 Catalytic studies of Cu2 (BDC)2 (DABCO) on C–C coupling reaction (2)
Scheme 3.4. The direct C-C coupling reaction via methylation and C-H
functionalization of N-methylaniline and phenylacetylene.
All optimized synthetic conditions of reaction 2 between Nmethylaniline and phenylacetylene are summaried in Table 3.4.
Reaction conditions
Temperature
Results (Reaction conversion (%))
RT (3), 100 °C (37), 110 °C (67), 120 °C
(96)
Molar ratio of Phenylacetylene :
1:1 (79), 1: 2 (96), 1:3 (96)
N-methylaniline
Catalyst amount (%)
Oxidant
Oxidant concentration (equiv)
Solvent
0 % (11), 1 % (83), 3 % (89), 5 % (96), 7
%(96)
TBHP (96), TBHP in decane (100), DTBP
(44),
K2 S2 O8 and Dilauroyl peroxide (no product)
1 (54), 1.5 (76), 2 (83), 3 (96)
DMA (96), DMF (82), NMP (97, byproduct), DEF (56), Clorobenzene (57),
Diclorobenzene
(73), o-xylene
(54),
Other Cu-MOFs, Cu salts
Other MOFs
Leaching test
Mesitylene (45)
Similar to Cu2 (BDC)2 (DABCO)
No product appeared
5 mol%
100
100
80
Conversion (%)
Conversion (%)
80
60
40
40
20
20
0
0
0
30
60
90
120
Time (min)
150
Figure 3.22. Leaching test
indicated no contribution from
homogeneous catalysis of active
species leaching into reaction
solution
60
180
1
2
3
4
5
6
Run
7
8
9
10
Figure 3.24. Catalytic recycling
studies.
Leaching test indicated no contribution from homogeneous catalysis of
active species leaching into reaction solution (Fig. 3.22).
The Cu2 (BDC)2 (DABCO) catalyst could be recovered and reused ten
times in the direct C-C coupling reaction between N-methylaniline and
phenylacetylene without a significant degradation in catalytic activity.
Indeed, a conversion of 96% was still obtained after 180 min for the
transformation in the ten run (Fig. 3.24).
With various coupling starting materials of N-methylanilines and
terminal alkynes, all the products were characterized by 1 H NMR. The
yields were isolated yields. The results showed that the isolated yields
were achieved from 58% to 77%.
FT-IR analysis of the reused Cu2 (BDC)2 (DABCO) exhibited a slightly
different absorption as compared to that of the fresh Cu-MOF. The
crystallinity of the reused Cu-MOF was found to be slightly different to
that of the fresh catalyst. However, XRD result indicated that the
reused Cu2 (BDC)2 (DABCO) was still highly crystalline.
3.3.3. Catalytic studies of Cu2 (BPDC)2 (BPY) on C–C coupling reaction (3)
Scheme 3.5. The A3 reaction of tetrahydroisoquinoline, benzaldehyde, and
phenylacetylene using Cu2 (BPDC)2 (BPY) catalyst.
All optimized synthetic conditions of reaction 3 from
Tetrahydroisoquinoline, benzaldehyde and phenylacetylene are
summaried in Table 3.5.
Reaction conditions
Temperature
Molar ratio of Phenylacetylene :
Benaldehyde:
Tetrahydroisoquinoline
Catalyst amount (%)
Solvent
Pyridine (equiv)
Adding product
Other Cu-MOFs, Cu salts
Results (Reaction conversion (%))
RT (10), 60 °C (20), 70 °C (46), 80 °C
(95), 90 (96)
1:1:1 (88), 1:1.1: 1.1 (95), 1:1.2: 1.2 (96),
1:1.5: 1.5 (96)
0 % (10), 1 % (32), 3 % (66), 5 % (95)
Toluene (95), p-xylene (52), metylsilene
(36), NMP (31), DMA (80), 1,4-dioxane
(39)
As a catalyst poison with copper sites
Product adsorbed on the copper sites of
Cu2 (BPDC)2 (BPY)
Higher than other Cu-MOFs, similar to Cu
salts
Other MOFs
No product appeared
Interestingly,
the
Cu2 (BPDC)2 (BPY)-catalyzed
C1-alkynylation
reaction of tetrahydroisoquinoline offered high regioselectivity to the
endo-yne-product. Indeed, more than 99% of (A) was achieved, leaving
less than 1% of (B) in the product mixture.
5 mol%
Leaching test
80
80
% Selectivity
100
Conversion (%)
100
60
40
60
40
20
20
0
0
0
30
60
90
120
150
180
1
2
3
4
Run
5
6
7
Time (min)
Figure 3.35. Leaching test indicated
no contribution from homogeneous
catalysis of active species leaching
into reaction solution
Figure 3.36. Catalyst recycling
studies
Fig. 3.35 indicated that no contribution from homogeneous catalysis of
active species leaching into reaction solution after Cu2 (BPDC)2 (BPY)
catalyst was removed.
The Cu2 (BPDC)2 (BPY) catalyst could be recovered and reused several
times for the copper-catalyzed A3 reaction of tetrahydroisoquinoline,
benzaldehyde, and phenylacetylene without a significant degradation in
catalytic activity. Indeed, a conversion of more than 95% was still
achieved in the 7th run (Fig. 3.36).
As compared to the FT-IR result of the fresh Cu2 (BPDC)2 (BPY), the
spectra of reused Cu-MOF exhibited a similar absorption. Moreover,
the XRD result of the recovered Cu2 (BPDC)2 (BPY) indicated that the
- Xem thêm -