Synthesis of 2-aminobutene-1,4-diones by gold-catalysed three-component coupling reactions

Article abstract of DOI:10.3184/174751916X14579667880206

A gold-catalysed three-component coupling reaction of phenylglyoxal derivatives, alkynes and secondary amines was developed to provide a novel one-pot synthesis of 2-aminobutene-1,4-diones in moderate to good yields.

Full text of DOI:10.3184/174751916X14579667880206

JOURNAL OF CHEMICAL RESEARCH 2016
VOL. 40 APRIL, 247–249
RESEARCH PAPER 247
Synthesis of 2-aminobutene-1,4-diones by gold-catalysed three-component
coupling reactions
Li Liu*, Jiaqi Tang, Jian Qiang and Mingyang He
School of Petrochemical Engineering, Changzhou University, Changzhou 213164, P.R. China
A gold-catalysed three-component coupling reaction of phenylglyoxal derivatives, alkynes and secondary amines was developed to
provide a novel one-pot synthesis of 2-aminobutene-1,4-diones in moderate to good yields.
Keywords: 2-aminobutene-1,4-dione, gold-catalysis, phenylglyoxal derivative, secondary amine, alkynes, three-component coupling reaction
Compounds which have the 2-aminobutene-1,4-dione skeleton
can be found in many drugs, bio-active compounds and industrial
products.1–4 Additionally, these 2-aminobutene-1,4-diones can
also serve as useful tools for constructing heterocyclic compounds
in organic synthesis containing, for example, pyrrole, hydrazine,
furan and cyclopentenone moieties.5–8 As a consequence, various
methods for their preparation have been reported previously,
for example, conjugate addition of diaroylacetylenes or sulfur
ylides to aryl azides,9,10 using α,β-unsaturated γ-dicarbonyl or
acetophenones with amines,11,12 reaction of pyridinium bromides
and primary aromatic amines with phenylglyoxal or ethyl
glyoxalate13 and other ways.14,15 Recently, Wu and co-workers
developed an efficient Cu-catalysed tandem reaction to synthesise
2-aminobutene-1,4-diones in good yields, but a long reaction time
is needed.16 Here, we develop a simple and convenient method
by a multi-component reaction process to access 2-aminobutene-
1,4-diones rapidly.
Gold catalysis offers new ways for the efficient construction
of complex molecules and has attracted much attention because
of the catalyst’s soft and carbophilic Lewis acidity in recent
years.17–20 Furthermore, Au-catalysed reactions generally proceed
under very mild conditions with small amounts of catalyst. In
2013 we reported a new gold-catalysed three-component coupling
(TCC) reaction of phenylglyoxal derivatives, secondary amines
and alkynes under an N2 atmosphere.21 This method afforded
the efficient synthesis of three-substituted furans in good yields
and provided a powerful approach for the preparation of furan
derivatives. Meanwhile, Hashmi and co-workers demonstrated a
reaction to form 1,2-dicarbonyl-3-enes with the same substrates
under AuCl catalysis.22 Secondary amine mediated alkyne-to-
allene isomerisation and hydrolysis of the enamine substructure
during the work-up delivered the formal hydroacylation products.
During our previous work, we found traces of 2-aminobutene-1,4-
diones formed under aerobic conditions with gold catalysts, so we
decided to study this product. Now we wish to introduce a gold-
catalysed one-pot, three-component synthesis of 2-aminobutene-
1,4-dione derivatives utilising the same substrates (phenylglyoxal
derivatives, secondary amine and alkynes) in the presence of
H2O (Scheme 1).
Results and discussion
Initially, phenylglyoxal monohydrate (1a), morpholine (2a) and
phenylacetylene (3a) were chosen as the model substrates to
determine the catalytic activity of different metal catalysts under
an O2 atmosphere (Table 1). Among the various metal catalysts,
AuBr3 was found to be the most effective catalyst for this TCC
transformation affording the product in 34% yield (Table 1, entry
5). This reaction did not work in the absence of any catalyst
(Table 1, entry 1). CuI showed no catalytic activity to the reaction
(Table 1, entry 2). We were happy to find that a yield of 82% of
4a was formed using 5 mol% AuBr3 in MeOH/H2O (ratio of 10:1)
at 50 °C after 5 h (Table 1, entry 7), while using H2O only led to
a lower yield (Table 1, entry 8). Various other solvents such as
DMF, THF and toluene were also used for the reaction but none
of them could produce a higher yield, even at higher temperature
(Table 1, entries 9–12).
With the optimised reaction conditions in hand, the scope
of this TCC reaction was explored. As shown in Table 2, the
results revealed that all the desired products could be obtained
in moderate to good yields. Alkyne substrates bearing electron-
withdrawing groups or electron-donating groups were
converted efficiently into 2-aminobutene-1,4-dione products
O
[Au]
R4
Hashmi's work
R
O
O
R3
N
R2
O
R2
R3
[Au]
+
R4
Previous work
This work
+
O
N
R
R4
R
H
R2
N R3
[Au], H2O
O2 balloon
R4
R
O O
Scheme 1
* Correspondent. E-mail: liliuchem@163.com

248 JOURNAL OF CHEMICAL RESEARCH 2016
Table 1 Optimisation studies for the preparation of 4aa
Table 2 Gold-catalysed three-component coupling reaction to form E-2-
aminobutene-1,4-dionesa
O
R2
N
N
O
R3
O
[M], solvent
O2 balloon
O
R1
R2
R3
5 mol% AuBr3
O
Ph
R4
O
R4
N
H
Ph
N
H
2a
CH3OH/H2O, 50oC
O2 balloon
+
+
O
4a
O
R1
O
O
4
1a
3a
3
1
2
Product R1
Amine
R4
Yieldb/%
82
Entry Catalyst
T/°C
Solvent
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
Yieldb/%
0
4a
4b
4c
4d
4e
4f
1a; H
1a
2a; morpholine
3a; C6H5
3b; 4-FC6H4
1
None
CuI
25
25
25
25
25
50
50
50
50
50
50
110
2a
85
2
0
1a
2a
3c; 4-CH3C6H4
67
3
AuCl
16
1a
2a
3d; 4-C5H11C6H4
71
4
AuCl3
AuBr3
AuBr3
AuBr3
AuBr3
AuBr3
AuBr3
AuBr3
AuBr3
11
1b; 2-Cl
1c; 4-Cl
1d; 4-br
1a
2a
3a
3a
3a
3a
3c
3a
3a
54
5
34
42
82
19
2a
58
6
4g
4h
4i
2a
72
7
MeOH/H2O (10:1)
H2O
2b; piperidine
76
8
1a
2b
73
9
DMF
16
4j
1c
2b
51
10
11
12
THF
31
4k
1a
2c; diethylamine
62
Toluene
Toluene
34
25
aReaction conditions: 1 (0.20 mmol), 2a (0.25 mmol), AuBr3 (0.02 mmol), MeOH/H2O
(2.0 mL), at 50 °C under O2, 6h.
bIsolated yield.
aStandard reaction conditions: 1a (1.0 mmol), 2a (1.5 mmol), 3a (2.0 mmol), catalyst
(5 mol%), solvent (2.0 mL) were heated in a tube under O2, 6 h.
bIsolated yield.
O
R1
R2
O
R2 R3
- H2O
R3
N
R3
R1
N
N
CHO
R2
HO
N
H
R1
R1
R2
5
R3
O2
R4
1
2
O
- H2O, - [Au]
O O
R4
[Au]
O
HO
R4
[Au]
H2O
R4
8
4
R4
[Au]
[Au]
7
3
6
Fig. 1 Proposed reaction mechanism and possible explanation of the observed stereochemistry.
Experimental
with good yields (products 4b–d and 4i). A long chain alkyl-
substituted aryl alkyne such as 1-ethynyl-4-pentylbenzene
could also be smoothly transformed into the desired product in
71% yield (4d). Reaction of different phenylglyoxal derivatives
was then examined. Phenylglyoxal derivatives with electron-
withdrawing groups at the para- or ortho-position of the aryl
ring all delivered the desired products in moderate yields
(products 4e–g and 4j). Finally, with respect to amines, those
such as morpholine or piperidine reacted smoothly under these
mild reaction conditions. It is noteworthy that an acyclic amine,
diethylamine, was also suitable for the reaction to give 4k in
62% yield. However, aromatic amines such as diphenylamine
could not be used for this reaction.
All experiments were conducted under an O2 atmosphere. All solvents
were commercially available. For column chromatography, 200–300
mesh silica gel was employed. H NMR and 13C NMR were recorded
1
on Bruker Advance 300, 400 or 500 MHz spectrometers in CDCl3
solution and the chemical shifts were reported in parts per million (δ)
relative to internal standard TMS (0 ppm). HRMS was performed on
a TOF Agilent 6540 instrument. Melting points were determined with
a WRS-1B apparatus and were uncorrected. Unless otherwise noted,
materials obtained from commercial suppliers were used without
further purification. Compounds 4a, 4h and 4k are reported in the
literature.16 Others are new compounds.
General procedure
The structures of the prepared diones 4a–k were fully
characterised by 1H NMR, 13C NMR and HRMS. Results were
in agreement with the proposed structures. The characteristic
NMR (CDCl3) features for 2-aminobut-2-ene-1,4-dione
H-19/H-20 signals (6.08–6.15 ppm) and C-19/C-20 signals
(91.73–93.70 ppm), demonstrated that the molecules adopted an
E-configuration.
A solution of phenylglyoxal derivative (1.0 mmol), amine (1.5 mmol),
AuBr3 (8.7 mg, 0.02 mmol) and alkyne (2.0 mmol) in solvent (MeOH/
H2O = 10/1, 2.0 mL) was heated to 50 °C under O2 for 6 h. After
completion of the reaction (observed on TLC), the solvent was evaporated
under reduced pressure to obtain the crude mixture. The residues were
purified by silica gel column chromatography [ethyl acetate/ petroleum
ether (b.p. 60–90 °C) = 1/10–1/4] to afford the pure product.
A plausible mechanism is proposed in Figure 1. Condensation
of the phenylglyoxal with the amine initially affords the
corresponding imine 5. The alkyne was activated by the gold
catalyst and underwent nucleophilic attack by H2O to generate
intermediate 6.23–25 Subsequent nucleophilic attack of 7 on 5
afforded the 1,4-enedione 8, which could form the product 4 by
gold-catalysed aerobic oxidative dehydrogenation.26–28
(E)-2-Morpholino-1,4-diphenylbut-2-ene-1,4-dione (4a): Light
yellow solid; m.p. 169–171 °C (lit.16 171–172 °C); 1H NMR (400 MHz,
CDCl3): δ 8.02 (d, J = 7.5 Hz, 2H), 7.84 (d, J = 7.4 Hz, 2H), 7.57–7.55
(m, 1H), 7.49–7.44 (m, 3H), 7.36 (t, J = 7.8 Hz, 2H), 6.15 (s, 1H), 3.74
(br s, 4H), 3.42 (br s, 2H), 3.32 (br s, 2H); 13C NMR (75 MHz, CDCl3):
δ 193.9, 187.2, 160.9, 138.8, 135.7, 133.6, 131.7, 129.0, 128.2, 128.1,
127.7, 93.5, 66.2, 47.6; MS (EI) m/z: 322.14.

JOURNAL OF CHEMICAL RESEARCH 2016 249
(E)-4-(4-Fluorophenyl)-2-morpholino-1-phenylbut-2-ene-1,4-dione
(4b): Light yellow solid; m.p. 178–180 °C, 1H NMR (400 MHz, CDCl3):
δ 8.02 (d, J = 7.1 Hz, 2H), 7.85 (dd, J = 5.5, 8.8 Hz, 2H), 7.57–7.55 (m,
1H), 7.51–7.47 (m, 2H), 7.04 (t, J = 8.6 Hz, 2H), 6.09 (s, 1H), 3.74 (br s,
4H), 3.42 (br s, 2H), 3.32 (br s, 2H); 13C NMR (75 MHz, CDCl3): δ 193.8,
185.7, 163.3*, 161.2, 135.6, 133.7, 130.1 (d, JF–C = 8.9 Hz), 129.1, 128.1, 115.2
(d, JF–C = 21.6 Hz), 92.9, 66.2, 47.6; HRMS (ESI) calcd for C20H19FNO3:
340.1349; found: 340.1348.
134.4, 131.4, 129.4, 129.3, 128.2, 127.7, 92.2, 49.4, 23.9; HRMS (ESI) calcd
for C21H21ClNO2: [M + H]+: 354.1261; found: 354.1263.
(E)-2-(Diethylamino)-1,4-diphenylbut-2-ene-1,4-dione (4k): Light
1
yellow solid; m.p. 156–159 °C (lit16 159–162 °C); H NMR (400 MHz,
CDCl3): δ 8.01 (d, J = 7.2 Hz, 2H), 7.83 (d, J = 7.0 Hz, 2H), 7.54–7.52 (m,
1H), 7.47–7.42 (m, 3H), 7.38–7.36 (m, 2H), 6.00 (s, 1H), 3.47 (br s, 4H),
1.41 (br s, 3H), 1.10 (br s, 3H); 13C NMR (125 MHz, CDCl3): δ 193.6,
186.5, 160.6, 139.4, 135.9, 133.2, 131.1, 128.9, 128.1, 128.0, 127.6, 91.6,
46.2, 44.3, 14.3; MS (EI) m/z: 308.16.
*It is thought that this is part of the doublet for the C bonded to F, the
other part of which is overlapped.
(E)-2-Morpholino-1-phenyl-4-p-tolylbut-2-ene-1,4-dione (4c): Light
yellow solid; m.p. 176–178 °C. H NMR (400 MHz, CDCl3): δ 8.03 (d,
Electronic Supplementary Information
1
The ESI (NMR spectra of 4a–k) is available through:
stl.publisher.ingentaconnect.com/content/stl/jcr/supp-data
J = 7.8 Hz, 2H), 7.74 (d, J = 7.9 Hz, 2H), 7.55 (d, J = 7.2 Hz, 1H), 7.47 (t,
J = 7.6 Hz, 2H), 7.16 (d, J = 7.9 Hz, 2H), 6.15 (s, 1H), 3.73 (br s, 4H), 3.40
(br s, 2H), 3.30 (br s, 2H), 2.36 (s, 3H); 13C NMR (75 MHz, CDCl3): δ
186.9, 160.8, 142.3, 133.5, 129.0, 128.9, 128.1, 127.8, 93.5, 66.2, 47.6, 21.6;
HRMS (ESI) calcd for C21H22NO3: [M + H]+: 336.1599; found: 336.1601.
(E)-2-Morpholino-4-(4-pentylphenyl)-1-phenylbut-2-ene-1,4-dione
(4d): Light yellow solid; m.p. 185–187 °C; 1H NMR (400 MHz, CDCl3):
δ 8.03 (d, J = 7.5 Hz, 2H), 7.76 (d, J = 8.0 Hz, 2H), 7.56 (t, J = 7.3 Hz 1H),
7.48–7.45 (m, 2H), 7.17 (d, J = 8.0 Hz, 2H), 6.15 (s, 1H), 3.74 (br s, 4H),
3.41 (br s, 2H), 3.31 (br s, 2H), 2.60 (t, J = 7.6 Hz, 2H), 1.59 (m, 2H), 1.30
(s, 4H), 0.87 (t, J = 6.5 Hz, 3H); 13C NMR (125 MHz, CDCl3): δ 194.0,
186.9, 160.7, 147.2, 136.4, 135.8, 133.5, 128.9, 128.3, 128.1, 127.8, 93.7,
66.2, 47.6, 35.8, 31.4, 30.8, 22.5, 13.9; HRMS (ESI) calcd for C25H30NO3:
[M + H]+: 392.2225; found: 392.2230.
We are grateful to the National Natural Science Foundation of
China (21402013), the Natural Science Foundation of Jiangsu
(BK20140259, 14KJB150002) and the Advanced Catalysis
and Green Manufacturing Collaborative Innovation Centre of
Changzhou University for generous financial support of our
research.
Received 20 November 2015; accepted 24 February 2016
Paper 1503726 doi: 10.3184/174751916X14579667880206
Published online: 28 March 2016
(E)-1-(3-Chlorophenyl)-2-morpholino-4-phenylbut-2-ene-1,4-dione
(4e): Light yellow solid; m.p. 177–179 °C; 1H NMR (400 MHz, CDCl3):
δ 8.00 (t, J = 1.7 Hz, 1H), 7.90–7.88 (m, 1H), 7.84–7.83 (m, 2H), 7.55–7.52
(m, 1H), 7.47–7.35 (m, 4H), 6.16 (s, 1H), 3.76 (br s, 4H), 3.43 (br s, 2H),
3.32 (br s, 2H); 13C NMR (100 MHz, CDCl3): δ 187.4, 160.4, 138.5, 137.4,
135.3, 133.5, 131.9, 130.4, 128.3, 127.8, 126.1, 93.8, 66.1, 47.7; HRMS (ESI)
calcd for C20H19ClNO3: [M + H]+: 356.1053; found: 356.1059.
(E)-1-(4-Chlorophenyl)-2-morpholino-4-phenylbut-2-ene-1,4-dione
(4f): Light yellow solid; m.p. 176–178 °C; 1H NMR (400 MHz, CDCl3):
δ 7.89 (d, J = 8.5 Hz, 2H), 7.83 (d, J = 7.4 Hz, 2H), 7.62 (d, J = 8.5 Hz, 2H),
7.47–7.44 (m, 1H), 7.37 (t, J = 7.4 Hz, 2H), 6.15 (s, 1H), 3.75 (br s, 4H), 3.41
(br s, 2H), 3.30 (br s, 2H); 13C NMR (125 MHz, CDCl3): δ 192.9, 187.3,
160.4, 138.5, 134.5, 132.4, 131.9, 129.5, 128.8, 128.3, 127.8, 93.7, 66.2, 47.6;
HRMS (ESI) calcd for C20H19ClNO3:[M + H]+: 356.1053; found: 356.1055.
(E)-1-(4-Bromophenyl)-2-morpholino-4-phenylbut-2-ene-1,4-dione
(4g): Light yellow solid; m.p. 177–179 °C; 1H NMR (400 MHz, CDCl3):
δ 7.89 (d, J = 8.3 Hz, 2H), 7.82 (d, J = 7.6 Hz, 2H), 7.61 (d, J = 8.3 Hz,
2H), 7.46–7.44 (m, 1H), 7.37 (t, J = 7.5 Hz, 2H), 6.15 (s, 1H), 3.75 (br s,
4H), 3.40 (br s, 2H), 3.30 (br s, 2H); 13C NMR (125 MHz, CDCl3): δ 192.9,
187.3, 160.5, 138.5, 134.6, 132.4, 131.8, 129.5, 128.8, 127.7, 93.7, 66.2,
47.6; HRMS (ESI) calcd for C20H19BrNO3: [M + H]+: 400.0548; found:
400.0542.
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(E)-1,4-Diphenyl-2-(piperidin-1-yl)but-2-ene-1,4-dione (4h): Light
1
yellow solid; m.p. 166–169 °C (lit.16 169–171 °C); H NMR (400 MHz,
CDCl3): δ 8.03 (dd, J = 8.5 Hz, 1.5 Hz, 2H), 7.84 (dd, J = 8.4 Hz, 1.5 Hz,
2H), 7.57–7.52 (m, 1H), 7.48–7.46 (m, 2H), 7.43–7.39 (m, 1H), 7.37–7.32
(m, 2H), 6.11 (s, 1H), 3.37 (br s, 4H), 1.66 (br s, 6H); 13C NMR (125 MHz,
CDCl3): δ 194.3, 186.8, 161.0, 139.3, 135.9, 133.3, 131.2, 128.9, 128.1, 127.7,
92.0, 49.1, 25.7, 23.9; MS (EI) m/z: 320.16.
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(E)-1-Phenyl-2-(piperdin-1-yl)-4-p-tolylbut-2-ene-1,4-dione
(4i):
Light yellow solid; m.p. 173–175 °C; 1H NMR (300 MHz, CDCl3): δ 8.03
(d, J = 7.3 Hz, 2H), 7.74 (d, J = 8.0 Hz, 2H), 7.55–7.52 (m, 1H), 7.45 (t,
J = 7.6 Hz, 2H), 7.15 (d, J = 7.9 Hz, 2H), 6.09 (s, 1H), 3.40–2.25 (br m,
4H), 2.35 (s, 3H), 1.7–1.55 (br s, 6H); 13C NMR (75 MHz, CDCl3): δ 194.3,
186.6, 160.8, 141.7, 136.6, 136.0, 133.2, 131.6, 129.0, 128.8, 128.3, 127.8,
126.8, 92.1, 25.6, 23.9, 21.5; HRMS (ESI) calcd for C22H24NO2: [M + H]+:
334.1807; found: 334.1810.
(E)-1-(4-Chlorophenyl)-4-phenyl-2-(piperidin-1-yl)but-2-ene-1,4-
1
dione (4j): Light yellow solid; m.p. 177–179 °C; H NMR (400 MHz,
CDCl3): δ 7.98 (d, J = 8.2 Hz, 2H), 7.84 (d, J = 7.6 Hz, 2H), 7.45–7.42 (m,
2H), 7.38–7.34 (m, 3H), 6.10 (s, 1H), 3.4–3.2 (br m, 4H), 1.7–1.55 (br m,
6H); 13C NMR (125 MHz, CDCl3): δ 193.0, 187.0, 160.5, 139.6, 139.1,