A recyclable metal-organic framework MOF-199 catalyst in coupling and cyclization of β-bromo-α,β-unsaturated carboxylic acids with terminal alkynes leading to alkylidenefuranones

Article abstract of DOI:10.1016/j.jorganchem.2015.05.040

β-Bromo-α,β-unsaturated carboxylic acids react with terminal alkynes in DMF in the presence of a catalytic amount of metal-organic framework MOF-199 along with a base under microwave irradiation to afford the corresponding alkylidenefuranones in good yiel

Full text of DOI:10.1016/j.jorganchem.2015.05.040

Journal of Organometallic Chemistry 791 (2015) 13e17
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Communication
A recyclable metal-organic framework MOF-199 catalyst in coupling
and cyclization of -bromo- -unsaturated carboxylic acids with
b
a,b
terminal alkynes leading to alkylidenefuranones
Son Long Ho, Il Chul Yoon, Chan Sik Cho*, Heung-Jin Choi
Department of Applied Chemistry, Kyungpook National University, Daegu 702-701, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
b
-Bromo-a,b-unsaturated carboxylic acids react with terminal alkynes in DMF in the presence of a
Received 17 February 2015
Received in revised form
19 May 2015
Accepted 23 May 2015
Available online 27 May 2015
catalytic amount of metal-organic framework MOF-199 along with a base under microwave irradiation to
afford the corresponding alkylidenefuranones in good yields. The catalytic system could be easily
recovered and reused 5 times without any loss of catalytic activity.
© 2015 Published by Elsevier B.V.
Keywords:
MOF-199
Sonogashira coupling
b
-Bromo-
a,b-unsaturated carboxylic acids
Heterocycles
Terminal alkynes
1. Introduction
present work was disclosed during the discovery of a reusable
catalyst alternative for such coupling and cyclization. Metal-organic
It is known that many furanone-containing compounds exhibit
a wide spectrum of biological activities such as antibacterial,
cytotoxic, antimicrobial, antibiotic, and antitumor [1]. Thus, many
furanone-containing compounds have been synthesized and tested
for biological activity [1]. In connection with this report, during the
course of our continuing studies directed towards transition metal-
frameworks (MOFs) have been widely used as materials in
numerous fields [6]. Besides such exploitations, quite recently, it is
also known that MOFs are used as a catalyst or catalyst support for
versatile organic and organometallic reactions [7]. Under these
circumstances, this report describes
catalyzed coupling and cyclization of
a
recyclable MOF-199-
b
-bromo- -unsaturated
a,b
catalyzed cyclization reactions of
hydes and their derivatives, we have identified several new
b
-bromo-
a
,
b
-unsaturated alde-
carboxylic acids with terminal alkynes leading to alkylidenefur-
anones under microwave irradiation [8].
methods for the synthesis of carbo- and heterocyclic compounds
[2].
b
-bromo-
a
,
b
-unsaturated aldehydes and their derivatives are
-methylene group-containing ketones by
2. Results and discussion
readily prepared from
a
bromination under Vilsmeier-Haack conditions [3], and the prod-
ucts can serve as valuable building blocks for the construction of
various cyclic compounds [4]. Among such cyclization reactions, we
First we optimized the conditions for the coupling and cycliza-
tion of 2-bromocyclohex-1-enecarboxylic acid (1a) with phenyl-
acetylene (2a) (Table 1). Treatment of acid 1a with 1.5 equivalent of
2a in DMF at 100 ꢀC for 15 min in the presence of a catalytic amount
of MOF-199 and K2CO3 under microwave irradiation (100 W initial
power) gave (3Z)-3-benzylidene-4,5,6,7-tetrahydroisobenzofuran-
1(3H)-one (3a) in 69% isolated yield with incomplete conversion of
1a (entry 1). Increasing the initial microwave power to 200 W gave
no significant change in 3a yield (entry 2). The yield of 3a increases
on prolonging the reaction time to 30 min with complete conver-
sion of 1a, which was monitored until 1a had disappeared on thin-
have shown that
b-bromo-a,b-unsaturated carboxylic acids are
coupled and cyclized with terminal alkynes in the presence of Pd on
C/PPh3 or CuI/amino acid to give alkylidenefuranones [5]. However,
these protocols have some drawbacks requiring an expensive
consumable transition metal catalyst or an additional ligand. The
* Corresponding author.
E-mail address: cscho@knu.ac.kr (C.S. Cho).
http://dx.doi.org/10.1016/j.jorganchem.2015.05.040
0022-328X/© 2015 Published by Elsevier B.V.

14
S.L. Ho et al. / Journal of Organometallic Chemistry 791 (2015) 13e17
Table 1
carboxylic acids 1h and 1i were employed. Even though the
coupling and cyclization took place irrespective of the position,
higher product yield was observed with 1h. As is case for the re-
Optimization of conditions for the reaction of 1a with 2a.a
O
O
action of 1h with 2a under CuI/ -proline system, the product 3l was
L
obtained as stereoisomeric mixture [5b]. Here again (Z)-isomer was
formed in preference to (E)-isomer. In the reaction with 1i, (Z)-3-
benzylidenenaphtho[2,1-c]furan-1(3H)-one (3m) was produced
by dehydrogenation of (Z)-3-benzylidene-4,5-dihydronaphtho[2,1-
c]furan-1(3H)-one initially formed by intrinsic coupling and cycli-
zation between 1i and 2a under the employed conditions. The high
resolution mass spectrum of 3m shows peak at m/z ¼ 272.0835
(Mþ,100% intensity). Similar dehydrogenation was observed by our
OH
MOF-199, base, solvent
Microwave irradiation
O
Ph
Br
Ph
1a
2a
3a
Entry
Bases
Solvents
Temp (ꢀC)
Time (min)
Yield (%)
1
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
K3PO4
NaOtBu
Cs2CO3
NaOAc
Bu3N
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
100
100
100
30
15
15
30
30
30
30
30
30
30
30
30
30
30
30
69
71
81
0
22
68
63
60
68
60
0
2b
3
recent report on the coupling and cyclization of
saturated amides with formamide [9].
b-bromo-a,b-un-
4
5
6
7
8
9
10
11
12
13
14
The configuration of stereoisomeric product 3m was clarified by
quantum chemical calculations compared with observed NMR
chemical shifts. On two possible (E)- and (Z)-stereoisomers the
energy-minimized geometry, energy and chemical shift calcula-
tions were performed based on density functional theory (DFT)
with B3LYP functional as implemented in the Spartan program [10].
The energetics and chemical shifts of each geometry were calcu-
lated using high level 6-311G* basis set.
50
100
100
100
100
100
100
100
100
100
e
0
69
65
K2CO3
K2CO3
Toluene
1,4-Dioxane
Shown in Fig. 1 are electrostatic potential maps on ball-and-
spoke of each isomer. It is easily recognized that (Z)-stereoisomer
is more stable than (E)-isomer destabilized due to steric hindrance
caused between phenyl and naphtofuranone moieties. These two
aromatic planes are planar for (Z)-isomer, but almost orthogonal for
a
Reaction conditions: 1a (0.3 mmol), 2a (0.45 mmol), MOF-199 (0.03 mmol), base
(0.6 mmol), solvent (3 mL), 100 ꢀC, under microwave irradiation (100 W initial
power).
b
200 W initial power.
(E)-isomer, resulting in destabilization due to the
p-electron
layer chromatography (entry 3). The reaction did not proceed at all
at 30 ꢀC and lowering the reaction temperature to 50 ꢀC resulted in
lower yield of 3a (entries 4 and 5). The reaction also proceeded in
the presence of other inorganic bases such as Na2CO3, K3PO4,
NaOtBu, Cs2CO3, and NaOAc, but the yields of 3a were generally
lower than that obtained in the presence of K2CO3 (entries 6e10).
However, the reaction did not proceed at all in the presence of
organic base or in the absence of base (entries 11 and 12). Among
the solvents examined, DMF was found to be that of choice (entries
13 and 14). The best results in terms of the yield of product 3a and
complete conversion of 1a were achieved by the using the set of
reaction conditions shown in entry 3 of Table 1.
deconjugation of (E)-isomer which is 6.05 kcal/mol more unstable
by DFT calculation. Also the chemical shift of the proton H8 of
naphthofuranone moiety is noticeably indicative to clarify whether
the obtained product is (Z)- or (E)-isomer, because the proton of
(E)-isomer is located just above phenyl ring due to steric hindrance,
which will be highly shielded by the magnetic anisotropic effect.
The DFT/6-311G* calculation predicted it resonancing at 6.65 ppm
instead of 7.80 ppm in the (Z)-isomer. The corresponding chemical
shift is observed at 7.78 ppm in CDCl3. This sharp doublet (J ¼ 8.4
Hz) of the proton is easily assignable from the other five protons on
the naphtofuranone moiety which are all doublets of doublet with
long-range coupling. The chemical shift of the vinylic proton is
further indicative, which is observed at 6.53 ppm. The DFT/6-311G*
calculation resulted in 6.46 ppm for (Z)-isomer and 7.24 ppm for
(E)-isomer. All calculations and observed chemical shifts support
that the isolated product has (Z)-configuration.
The initial model reaction between the acid 1a and alkyne 2a
was chosen to test recyclability of MOF-199 (recyclability test was
performed on 5 times larger scale). The recycling potential of the
catalytic system could be reused five times without any loss of
catalytic activity, the yield of 3a remained nearly constant from 1st
(81%), 2nd (81%), 3rd (80%), 4th (80%) to 5th (79%). XRD of the fresh
and reused (after fifth run) MOF-199 demonstrated that the crys-
tallinity of the catalyst was kept unchanged during the course of the
reaction (Fig. 2). The FT-IR spectra of the fresh and reused (after
fifth run) MOF-199 also exhibited nearly same absorption bands
(Fig. 3). Cu2 dimeric units in MOF-199 are coordinated by four
carboxylate ions as paddle-wheel and two water molecules in axial
positions [11]. The axial water molecules can be dissociated in DMF,
in which the axial sites show catalytic activities for the present
reaction.
Having optimized the reaction conditions, b-bromo-a,b-unsat-
urated carboxylic acids 1 were subjected to reaction with terminal
alkynes 2 to investigate the scope of the reaction and several
representative results are summarized in Table 2. 2-
Bromocyclohex-1-enecarboxylic acid (1a) reacted with aryl al-
kynes (2b and 2c) having electron-donating and ewithdrawing
group substituents on aromatic ring and the corresponding ben-
zylidenefuranones (3b and 3c) were produced invariably irre-
spective of the electronic nature of such substituents. The acid 1a
also coupled and cyclized with terminal alkynes (2e and 2f) having
straight and branched alkyl chains to give the corresponding
alkylidenefuranones (3d and 3e) in good yields. These results
clearly indicate that the present catalytic system exhibit higher
catalytic activity compared with Pd on C/CuI/PPh3 and CuI/
[5]. The yields under both catalytic systems are shown in paren-
theses of Table 2. The coupling and cyclization of six-membered
bromo- -unsaturated carboxylic acids 1b and 1c reacted with
L-proline
b
-
a,b
terminal alkynes to give the corresponding furanones in similar
yields, irrespective of the presence of the methyl and phenyl sub-
stituents on 1b and 1c. With cyclic b-bromo-a,b-unsaturated car-
boxylic acids (1d-g) having various ring sizes, the corresponding
coupled and cyclized benylidenefuranones 3h-k were also formed
in 72e84% yields, and the product yield was not significantly
affected by the ring size. To test for the effect of the position of
3. Conclusion
In summary, it has been shown that b-bromo-a,b-unsaturated
carboxylic acids are coupled and cyclized with terminal alkynes in
the presence of a catalytic amount of MOF-199 along with a base to
bromide and carboxy group on
b-bromo-a,b-unsaturated

Table 2
MOF-199-catalyzed synthesis of furanones 3 f rom 1 and 2.a
O
O
OH
Br
MOF-199, K2CO3, DMF
Microwave irradiation
O
R
R
1
2a R = Ph
2b
3
R = 4-MeC6H4
2c R = 4-FC6H4
2d
2e
R = butyl
R = hexyl
2f R = isobutyl
Yieldb (%)
1
2
Alkynes
Carboxylic acids
Furanones 3
O
O
OH
O
Br
R
1a
2a
2b
2c
2e
2f
3a
3b
3c
3d
3e
81 (60)
71 (51)
74 (55)
72 (51)c
54
O
O
OH
O
Br
Ph
1b
2a
2d
3f
81 (65)
O
O
Ph
Ph
OH
O
Br
Bu
59 (51)c
1c
3g
O
O
OH
O
Br
Ph
1d
1e
2a
2a
3h
3i
72 (50)
84 (70)
O
O
OH
O
Br
O
Ph
O
OH
O
Br
Ph
1f
2a
2a
3j
75 (42)
73 (56)
O
O
OH
O
Br
Ph
1g
3k
O
O
OH
O
Br
Ph
71d (0)
1h
1i
2a
2a
3l
O
O
O
OH
Br
Ph
3m
21
a Reaction condition: 1 (0.3 mmol), 2 (0.45 mmol), MOF-199 (0.03 mmol), K2CO3 (0.6 mmol),
DMF (3 mL), 100 oC, 30 min, under microwave irradiation (100 W initial power).
b Yields under CuI/amino acids are shown in parentheses unless otherwise stated [5b].
c Under Pd on C/CuI/PPh3 catalytic system [5a].
d (E)- and (Z)-isomers were isolated in 25% and 46% yields, respectively.

16
S.L. Ho et al. / Journal of Organometallic Chemistry 791 (2015) 13e17
Fig. 1. Electrostatic potential maps on ball-and-spoke model of (Z)- and (E)-isomer of 3m as obtained with DFT/6-311G* calculation. The proton H8 of naphtofuranone moiety is
shown in green. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
give alkylidenefuranones in good yields. The MOF-199 catalyst
could be easily recovered by simple filtration and solvent washing
and reused 5 times without any loss of catalytic activity. Further
study of catalytic applications of the present recyclable MOF-199
system to organic reactions is currently under investigation.
High-resolution mass spectrometry (HRMS) was performed with a
Jeol JMS-700 spectrometer at the Korea Basic Science Center, Daegu
Korea. The isolation of pure products was carried out via thin layer
(silica gel 60 GF254, Merck) chromatography. The starting
b-bromo-
a,b-unsaturated carboxylic acids were prepared via two steps from
the corresponding ketones according to literature procedures
[3,12]. Commercially available organic and inorganic compounds
were used without further purification.
4. Experimental
1H and 13C NMR (400 and 100 MHz) spectra were recorded on a
Bruker Avance Digital 400 spectrometer using TMS as an internal
standard. Melting points were determined on a Standford Research
Inc. MPA100 automated melting point apparatus. X-ray diffraction
4.1. General procedure for MOF-199-catalyzed coupling and
cyclization of b-bromo-a,b-unsaturated carboxylic acids with
terminal alkynes under microwave irradiation
experiments (XRD) were performed in a Bragg-Brentam
Rigaku D/Max-2500 diffractrometer using a Cu source working at
40 kV and 200 mA over the range of 5-90ꢀ (2
). FT-IR spectra (ATR)
q/2q
A 10 mL microwave reaction tube was charged with b-bromo-
a,b-unsaturated carboxylic acid 1 (0.3 mmol) and terminal alkyne 2
(0.45 mmol), together with MOF-199 (0.018 g, 0.03 mmol), K2CO3
q
were recorded on Shimadzu IR Prestige-21 spectrophotometer.
(0.083 g, 0.6 mmol), and DMF (3 mL). The mixture was heated to
100 C for 30 min by microwave irradiation (CEM Discover Micro-
ꢀ
wave System) at 100 W initial power. After cooling to room tem-
perature, the solid was filtered out, washed with water and MeOH,
and dried under vacuum. The recovered MOF-199 was subjected to
a second run by charging with 1, 2, K2CO3, and DMF (recyclability
test was performed on 5 times larger scale). Removal of the solvent
from the filtrate left an oil, which was purified by thin layer chro-
matography (silica gel, ethyl acetate/hexane) to give desired
products 3. Except for 3m, all products were characterized by
spectroscopic comparison with authentic samples synthesized by
our recent reports [5].
4.1.1. (Z)-3-Benzylidenenaphtho[2,1-c]furan-1(3H)-one (3m)
Solid, m.p. 133e134 ꢀC (from CH2Cl2-hexane); 1H NMR (CDCl3):
d
6.53 (s,1H), 7.35 (tt, J ¼ 7.2,1.4 Hz,1H), 7.45 (dd, J ¼ 7.4, 7.2 Hz, 2H),
Fig. 2. X-ray powder diffraction pattern of MOF-199: (a) fresh; (b) reused.
7.64 (dd, J ¼ 8.1, 7.7, 1.2 Hz, 1H), 7.75 (dd, J ¼ 8.0, 7.7, 1.6 Hz, 1H), 7.78
(d, J ¼ 8.4 Hz, 1H), 7.92 (td, J ¼ 7.4, 1.4 Hz, 2H), 7.97 (td, J ¼ 8.1 Hz,
1H), 8.15 (d, J ¼ 8.4 Hz, 1H), 8.92 (dd, J ¼ 8.0, 1.2 Hz, 1H); 13C NMR
(CDCl3):
d 108.51, 116.68, 117.96, 124.17, 127.86, 128.83, 128.87,
129.06, 129.19, 129.68, 130.61, 133.42, 133.97, 135.92, 141.56, 145.08,
167.50; HRMS (EI) Anal. Calc. for C19H12O2 (Mþ): 272.0837. Found:
272.0835.
Acknowledgement
This research was supported by Basic Science Research Program
through the National Research Foundation of Korea (NRF) funded
by the Ministry of Education, Science and Technology (2010-
0007563).
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