Addition of 1,3-dicarbonyl compounds to terminal alkynes catalyzed by a cationic cobalt(iii) complex

Article abstract of DOI:10.1039/d0ra05923d

The Nakamura reaction using a cationic cobalt(iii) complex, [Cp?Co(CH3CN)3][SbF6]2 as the catalyst under neutral and aerobic conditions at 110 °C has been described. In solution, the complex is expected to lose a hemilabile acetonitrile ligand to produce

Full text of DOI:10.1039/d0ra05923d

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Addition of 1,3-dicarbonyl compounds to terminal
alkynes catalyzed by a cationic cobalt(III) complex†
Cite this: RSC Adv., 2020, 10, 36014
*
Mohan Chandra Sau and Manish Bhattacharjee
The Nakamura reaction using a cationic cobalt(III) complex, [Cp*Co(CH3CN)3][SbF6]2 as the catalyst under
neutral and aerobic conditions at 110 ꢀC has been described. In solution, the complex is expected to lose
a hemilabile acetonitrile ligand to produce a highly electron-deficient cobalt(III) center, and the Lewis acidic
nature of the cobalt center has been exploited for the enolization of the dicarbonyl compounds. The
reaction of 1,3-dicarbonyl compounds with alkynes affords the corresponding alkenyl derivative.
However, the reaction of phenylacetylene and its derivatives with b-ketoesters affords corresponding
terphenyl compounds. Details of the mechanisms of the reactions have been proposed based on in situ
LCMS measurements.
Received 7th July 2020
Accepted 8th September 2020
DOI: 10.1039/d0ra05923d
rsc.li/rsc-advances
transition element has not been reported except a couple of
reports, one on Mn(CO)5Br (5 mol%)10 and another on
Cp*Co(CO)I2 (5 mol%) + Cu(OTf)2 (5 mol%)11 catalysed addition
Introduction
Atom economical carbon–carbon sigma bond formation under
neutral and mild conditions is an emerging eld in organic
synthesis due to the inertness of the C–C bond.1a It was believed
that the intermolecular addition of an enolate anion to an
unactivated alkene and alkynes is difficult due to the poor
polarity of C–C multiple bonds.1b However, Nakamura and
coworkers reported the addition of alkynes to b-ketoesters in
of dicarbonyl compounds to alkynes and (2 + 2 + 2) cycloaddi-
tion. All these methods either suffer from very harsh reaction
conditions or require expensive ligands or expensive additives.
It may be noted that the reactions catalysed by Cp*Co(CO)I2 and
Cu(OTf)2 are carried out at room temperature without using any
solvent. However, the catalyst and cocatalyst loading is
comparatively high. In the proposed mechanism of the reaction
it has been suggested that, Cu(OTf)2 is responsible for the
generation of Lewis acidic coordinatively unsaturated species
[Cp*Co(OTf)]+.11 Also, some of these metal complexes are air
and moister sensitive, so the reactions are carried out in dry
solvents under an inert atmosphere.
ꢀ
the presence of In(OTf)3 (0.05 to 5 mol%) at around 140 C in
the absence of any solvent.2 Later on, the same group developed
the asymmetric version of the reaction.3 These were followed by
several reports using other metal compounds. Lau and
coworkers have shown that TpRu[4-CF3C6H4N(PPh2)2](OTf) [Tp
¼ hydro(trispyrazolyl)borate] catalyses the addition 1,3-dike-
tones to terminal alkynes at 120 ꢀC under solvent-free condi-
tion.4 It has been shown that RuCl3$3H2O (5 mol%) in the
presence of Ag(PF6) (15 mol%) catalyses the addition of 1,3-
diketones to alkynes.5 Another report deals with [Ru(CO)3Cl2]2
catalysed addition of diketones to alkynes.6 However, the
conversions were poor, and in the cases of cyclic diketones,
instead of C–C bond formation, C–O bond formation was
observed. Xi et al. reported Nakamura reaction in presence of
0.05 mol% of [Xphos(TA)AuOTf] {TA ¼ 1,2,3-triazole} and
5 mol% of Ga(OTf)3.7 Another report deals with Ir(I) catalysed
Nakamura reaction.8 Kuninobu et al. reported that [Re(CO)3-
Br(THF)] (3 mol%) catalyses the Nakamura reaction at 50 ꢀC.9 It
may be noted that to the best of our knowledge to date Naka-
mura reaction catalysed by an earth abundant rst-row
It is anticipated that [Cp*Co(CH3CN)3]2+ can afford a coor-
dinatively unsaturated species, “[Cp*Co]2+” with very high Lewis
acidity during the reaction.
Multisubstituted benzene, especially terphenyl, are a very
important class of compounds.12,13 Conventional substitution
methods for the synthesis of multisubstituted benzene requires
a large number of steps.12 There are many reports on the tran-
sition metal-catalysed [2 + 2 + 2] cycloaddition reactions of
alkynes.14,15 However, due to the poor regioselectivity of the
reaction, it is challenging to synthesize multisubstituted
benzene.12 Apart from these reports, a few reports deal with the
synthesis of tetrasubstituted benzene from the reaction of b-
ketoesters with terminal alkynes catalysed by [ReBr(CO)4(-
THF)]12,13 in the presence of MS4A and N,N-dimethylacetamide
(20 mol%) and [MnBr(CO)5]12 in the presence of MS4A.
Herein we report [Cp*Co(CH3CN)3][SbF6]2 (I) catalysed the
addition of terminal alkynes to 1,3-diketones. We also report
the synthesis of tetrasubstituted benzene from the reaction of b-
ketoesters with terminal alkynes catalysed by I.
Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur
721302, India. E-mail: mxb@iitkgp.ac.in
† Electronic supplementary information (ESI) available: 1H and 13CNMR spectra
HRMS, and LCMS. See DOI: 10.1039/d0ra05923d
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Table 2 Reaction of diketones with the alkynes phenylacetylenea,b
Results and discussion
For the reaction of 1,3-diketones with terminal alkynes, the
reaction of 2,4-pentane-dione (1a) and phenylacetylene (2a) was
chosen as a model reaction for the for optimization. The reac-
tants 1a and 2a were taken in a reaction tube in dichloroethane
(DCE), and the reaction solution was heated at different
temperatures (room temperature to 110 ꢀC) for 24 hours, but we
could not detect any product formation (entry-1, Table 1). To
this reaction tube [Cp*Co(CH3CN)3][SbF6]2 (I) (1 mol%) was
added and was heated at 110 ꢀC for 12 hours. We could isolate
the desired product, 4-hydroxy-3-(1-phenyl vinyl)pent-3-en-2-
one (3a) in 48% yield in 12 hours (entry-2, Table 1). When
toluene was used as the solvent, 3a was isolated in 59% yield in
12 hours (entry-3, Table 1). All the subsequent reactions were
carried out in toluene. We thought that the addition of base
might facilitate enolate formation, and thus yield would
increase. Keeping this in mind, we carried out the reaction in
the presence of K2CO3 (1 equivalent), keeping all other reaction
conditions the same. However, the yield of 3a drastically
reduced (18%) (Table 1, entry 4). We then varied the concen-
tration of the catalyst. ꢀThe reaction carried out in the presence
of 2 mol% of I at 110 C afforded 3a in 67% yield in 10 hours
(Table 1, entry 5). The reaction carried out in the presence of
3 mol% of I at 90 ꢀC afforded 3a in 68% yield in 7 hours (Table 1,
entry 6). When the reaction was carried out at 110 ꢀC using
3 mol% I, the yield of 3a was 76% in 7 hours (Table 1, entry 7).
Further decrease in the reaction time to 5 hours did not affect
the yield (73%) of the product (Table 1, entry 8). We performed
the reaction using 4 mol% of I for 5 hours, but this did not
improve the yield of the product (Table 1, entry 9). The reaction
was also carried out in the presence of 3 mol% of I at 110 ꢀC for
7 hours. However, the yield was poor (46%) (Table 1, entry 10).
Having established the reaction condition, we proceeded to
investigate the substrate scope of the reaction. First, we carried
out the reaction of 2,4-pentane-dione with various alkynes. The
products, 3a to 3i, were isolated in 62 to 82% yield (Table 2). The
lowest yield (62% in 8 hours) was obtained in the case of 3-[1-
a
Reagents and conditions: alkyne (0.45 mmol), diketone (0.3 mmol), I
(3 mol%), temperature 110 ꢀC in toluene (2 ml). Yield: isolated.
b
Isolated yield. c From 1H NMR.
in the cases of 1-ethynyl-4-triuoromethyl-benzene (2g) (81%, 6
hours) and 1-ethynyl-4-nitro-benzene (2h) (82%, 7 hours). Other
products were isolated in approximately 75% yield. When we
carried reaction of 2-ethynyl-thiophene (2i) with 2,4-pentane-
dione (1a) the corresponding product, 4-hydroxy-3-(1-
thiophene-2-yl-vinyl)-pent-3-en-2-one (3i) was isolated in 74%
yield in 6 hours. However, the reaction of alkynes with the
aliphatic side chain failed to give the products. Next, we pro-
ceeded to explore the reactions of various acyclic and cyclic
diketones with alkynes.
(3,4-dichorophenyl)-vinyl]-4-hydroxy-pent-3-en-2-one
(3e).
Higher conversion to the corresponding product was observed
Table 1 Optimization of the reaction between phenylacetylene and 2,4-pentanedionea
I
Entry
(mol%)
Additive (mol%)
Temp (ꢀC)
Time (h)
Solvent
Yieldb (%)
1
2
3
4
5
6
7
8
9
—
1
1
1
2
3
3
3
4
3
—
—
—
90/110
90/110
110
110
110
100
90
110
110
12
12
12
12
10
7
7
5
5
7
DCE
DCE
—
48
59
18
67
68
76
73
75
46
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Neat
K2(CO)3 (1)
—
—
—
—
—
—
10
110
a
Reagents and conditions: 1a (0.45 mmol), 2a (0.3 mmol), solvent (4 ml). b Isolated.
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The reaction of 1-phenyl-1,3-pentane-dione with phenyl- mixture of 2,4-pentane-dione with phenylacetylene shows
acetylene was carried out under the same reaction condition. To a peak at m/z 293.1, which corresponds to [Cp*Co(acac)]+ ion.
our surprise, we obtained a mixture of E and Z isomers of Based on this observation, it is suggested that [Cp*Co(CH3-
Markovnikov addition product (3jb) as the major product and CN)3]2+ rst loses hemilabile acetonitrile ligands to generate the
anti-Markovnikov addition product (3ja) as the minor product. intermediate [Cp*Co(acac)]+ (A; Scheme 1). Another peak
The reaction of 2-methyl-2,4-pentane-dione with phenyl- appears at m/z 395.1, which corresponds to the intermediate
acetylene afforded 3-methyl-3-(1-phenyl vinyl)-pentane-2,4- [Cp*Co(acac)(PhCCH)]+ (B; Scheme 1). The intermediate B is
dione (3k) in 46% yield in 8 hours. The cyclic diketone, 2- highly electron decient, and the cobalt enolate attacks the
acetyl-cyclopentanone (1d) on reaction with phenylacetylene alkyne carbon bearing the substituent and produces species C.
(2a), and 1-ethynyl-4-methyl-benzene (2b) afforded the corre- It may be noted that we could not distinguish between the
sponding products, 3l and 3m in 79% and 68% yield in 6 hours, species B and C, as they have same m/z value. However, it is
respectively. The reaction of 2-acetyl-cyclohexanone (1e) with suggested that C is produced via the intermediate B. The species
phenylacetylene (2a) afforded 2-acetyl-2-(1-phenyl vinyl)- C reacts with another alkyne to produce the species D, for which
cyclohexanone (3n) in 71% yield in 6 hours. Our attempted a peak was observed at m/z 497.2. The species D then undergoes
reaction of phenylacetylene with 1,3-diphenyl-propane-1,3- protonolysis to produce the product and the intermediate B
dione failed to afford any product. Similarly, 5,5-dimethyl- back.
cyclohexane-1,3-dione did not afford any product. No product
In situ LCMS spectra were recorded at different time intervals
formation was observed when aliphatic alkynes were used.
of the reaction of methyl acetoacetate with phenylacetylene to
Aer carrying out the reaction of diketones, we thought to understand the possible mechanism of the reaction. In the
explore the reaction of b-ketoesters with alkynes catalysed by I. LCMS spectra of the reaction of methyl acetoacetate, a peak was
Thus, a reaction of 3-oxo-butyric acid methyl ester was carried observed at m/z 309.2, which corresponds to the species
out with phenylacetylene in the presence of 3 mol% I in toluene [Cp*Co(CH3COCHCOOMe)]+ (A, Scheme 2).
A peak was
at 110 ꢀC. To our surprise, we could not see the formation of the observed at m/z 513.4, which may be assigned to
expected product, 3-acetyl-3-phenyl-but-3-enoic acid methyl [Cp*Co(PhCCH)2(CH3COCHCOOMe)]+ (B; Scheme 2). The
ester, as obtained in the cases of diketones, described above. species B may undergo addition reaction to afford the species C.
Instead, we obtained 2-methyl-3,6-diphenyl benzoic acid methyl Because of this same m/z value, we could not distinguish
ester in a 60% yield in 12 hours (Table 3, entry 1). We then between B and C. We suggest that C is formed via the inter-
explored the substrate scope of the reaction, and the reactions mediate B. It is proposed that the species C undergoes [2 + 2]
of methyl acetoacetate (4a) and ethyl acetoacetate (4b) with cycloaddition and subsequent protonolysis to afford the
various alkynes were carried out, and the products were isolated product and the species A.
in good to moderate yield (52% to 69%) (Table 3).
Next, we proceeded to examine the mechanism by in situ
LCMS measurements. The in situ LCMS spectra of the reaction
Table 3 Reaction between b-ketoesters and alkynesa
Entry
Ester
Alkyne
Product
Time (h)
Yieldb (%)
a : b
1
2
3
4
5
6
4a
4a
4a
4a
4b
4b
2a
2b
2f
2g
2a
2b
5a
5b
5c
5d
5e
5f
12
16
16
16
18
16
60
62
55
52
62
69
1.3 : 1
1.4 : 1
1.3 : 1
1.3 : 1
1.5 : 1
1.8 : 1
a
b-Ketoester (0.3 mmol), & alkyne (2.5 equiv.), I (3 mol%), temperature
110 ꢀC. b Isolated yield.
Scheme 1 Plausible mechanism of addition 1,3-diketone to alkyne.
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column chromatography using hexane-ethyl acetate (0.2–5%) as
eluent.
4-Hydroxy-3-(1-phenylvinyl)pent-3-en-2-one2a
(3a).
Pale
yellow oil; yield 0.0447 g, 74%; 1H NMR (400 MHz, CDCl3):
d 16.64 (s, 1H), 7.43 (d, J ¼ 7.6 Hz, 2H), 7.39–7.28 (m, 3H), 5.91
(s, 1H), 5.24 (s, 1H), 1.99 (s, 6H); 13C NMR (100 MHz, CDCl3):
d 191.3, 143.5, 139.6, 128.7, 128.1, 125.9, 118.3, 113.9, 23.6.
4-Hydroxy-3-(1-p-tolylvinyl)pent-3-en-2-one4,5
(3b).
Pale
yellow oil; yield 0.0501 g, 77%; 1H NMR (400 MHz, CDCl3)
d 16.62 (s, 1H), 7.33 (d, J ¼ 8.0 Hz, 2H), 7.16 (d, J ¼ 8.0 Hz, 2H),
5.87 (s, 1H), 5.18 (s, 1H), 2.36 (s, 3H), 1.98 (s, 6H); 13C NMR (100
MHz, CDCl3): d 191.3, 143.2, 138.1, 136.8, 129.4, 125.8, 117.3,
114.0, 23.5, 21.1.
4-Hydroxy-3-(1-(4-methoxyphenyl)vinyl)pent-4-en-2-one4,5
(3c). Pale yellow oil; yield 0.0494 g, 71%; 1H NMR (400 MHz,
CDCl3) d 16.64 (s, 1H), 7.36 (d, J ¼ 8 Hz, 2H), 6.87 (d, J ¼ 8.0 Hz,
2H), 5.79 (s, 1H), 5.12 (s, 1H), 3.82 (s, 3H), 1.98 (s, 6H); 13C NMR
(100 MHz, CDCl3) d 191.3, 159.6, 142.7, 127.1, 116.3, 114.0, 55.3,
23.5.
Scheme 2 Plausible mechanism of addition b-ketoester to alkyne.
4-Hydroxy-3-(1-(4-chlorophenyl)vinyl)pent-4-en-2-one6 (3d).
Pale yellow oil; yield 0.0503 g, 71%; 1H NMR (400 MHz, CDCl3)
d 16.64 (s, 1H), 7.38 (d, J ¼ 8.8 Hz, 2H), 7.32–7.306 (m, 2H), 5.89
(s, 1H), 5.25 (s, 1H), 1.97 (s, 6H); 13C NMR (100 MHz, CDCl3):
d 191.3, 142.4, 139.4, 128.9, 127.2, 118.8, 99.9, 23.5.
4-Hydroxy-3-(1-(3,4-chlorophenyl)vinyl)pent-4-en-2-one (3e).
Pale yellow oil; yield 0.0505 g, 62%; 1H NMR (400 MHz, CDCl3)
d 7.50 (d, J ¼ 2.0 Hz, 1H), 7.42 (d, J ¼ 8.8 Hz, 1H), 7.27–7.23 (m,
1H), 5.92 (s, 1H), 5.31 (s, 1H), 1.97 (s, 6H); 13C NMR (100 MHz,
CDCl3) d 191.3, 141.5, 139.8, 133.1, 132.2, 130.7, 127.7, 125.1,
120.0, 112.9, 23.62. HRMS m/z calcd for C13H12O2Cl2Na+:
293.0112; found 293.0114.
Conclusion
In conclusion, a highly Lewis acidic complex of a rst raw
transition element, [Cp*Co(CH3CN)3][SbF6]2, has been used as
a catalyst for the Nakamura reaction. The same catalyst, when
employed for the reaction of b-ketoesters with the terminal
alkynes affords aromatic products. The mechanisms of the
reactions have been proposed based on the in situ LCMS
studies.
4-Hydroxy-3-(1-(4-uorophenyl)vinyl)pent-4-en-2-one4 (3f).
Pale yellow oil; yield 0.0490 g, 74%; 1H NMR (400 MHz, CDCl3)
d 16.63 (s, 1H), 7.40 (dd, J ¼ 8.8, 5.6 Hz, 2H), 7.04 (t, J ¼ 8.8 Hz,
2H), 5.84 (s, 1H), 5.21 (s, 1H), 1.98 (s, 6H); 13C NMR (100 MHz,
CDCl3) d 191.3, 162.9 (d, J ¼ 217.0 Hz), 142.4, 135.8, 127.6 (d, J ¼
8.1 Hz), 118.1, 115.7 (d, J ¼ 21 Hz), 113.7, 23.5.
Experimental section
General methods and materials
All the reactions were performed under aerial atmosphere
without further purication of commercially available reagents
and solvents. The catalyst [Cp*Co(CH3CN)3][SbF6]2 was
1
synthesized from the literature procedure.16 The H NMR (400
4-Hydroxy-3-(1-(4-tri-uoromethylphenyl)vinyl)pent-4-en-2-
one5 (3g). Pale yellow oil; yield 0.0659 g, 81%; 1H NMR (400
MHz, CDCl3) d 16.67 (s, 1H), 7.61 (d, J ¼ 8.4 Hz, 2H), 7.54 (d, J ¼
8.0 Hz, 2H), 6.00 (s, 1H), 5.37 (s, 1H), 1.98 (s, 6H); 13C NMR (100
MHz, CDCl3) d 191.3, 143.1, 142.4, 126.1, 125.7 (dd, J ¼ 7.0, 4.0
Hz), 120.7, 113.2, 23.6.
MHz) and 13C NMR (100 MHz) were recorded in CDCl3. The
LCMS data of the reaction mixture were recorded with a TOF
mass spectrometer in ESI+ mode in MeOH and acetonitrile
solvent. The HRMS data of newly synthesized compounds were
recorded with a TOF mass spectrometer in ESI+ mode in
acetonitrile/water mixture. Flash column chromatography was
done in silica gel (60–120 mesh) for purication of product from
the crude reaction mixture.
4-Hydroxy-3-(1-(4-nitrophenyl)vinyl)pent-4-en-2-one8
(3h).
Pale yellow oil; yield 0.0607 g, 82%; 1H NMR (400 MHz, CDCl3)
d 16.70 (s, 1H), 8.22 (d, J ¼ 8.8 Hz, 2H), 7.59 (d, J ¼ 8.4 Hz, 2H),
6.08 (s, 1H), 5.48 (s, 1H), 1.98 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 191.3, 147.5, 146.0, 142.0, 126.6, 124.1, 122.5, 112.8, 23.6.
General procedure for the reaction of alkynes with diketo
compounds
4-Hydroxy-3-(1-(thiophen-2-yl)vinyl)pent-3-en-2-one6
Yellow liquid; yield 0.0461 g, 74%; H NMR (500 MHz, CDCl3)
(3i).
1
The catalyst (0.0070 g, 3 mol%), toluene (2 ml), and the two d 16.6 (s, 1H), 7.33 (d, J ¼ 2.0 Hz, 1H), 7.28 (d, J ¼ 4.5 Hz, 1H),
reactants 1,3-diketone or b-ketoesters (0.3 mmol), terminal 7.09 (S, 1H), 5.81 (s, 1H), 5.16 (s, 1H), 2.01 (s, 6H); 13C NMR (100
alkyne (0.45 mmol) were taken in a screw-cap reaction tube. The MHz, CDCl3) d 191.2, 142.4, 138.6, 126.7, 125.1, 122.5, 117.1,
reaction tube was placed in an oil-bath having a temperature of 114.1, 23.3.
110 ꢀC–115 ꢀC. The reaction solution was stirred for 5–8 hours.
(Z)-3-Hydroxy-1-phenyl-2-(1-phenylvinyl)but-2-en-1-one5
The reaction was monitored by TLC. The solvent was evapo- (3ja). Liquid; yield of 3j 0.0437 g, 55%; 1H NMR (400 MHz,
rated, and the products were puried by silica gel (60–120 mesh) CDCl3) d 7.57 (d, J ¼ 7.6 Hz, 2H), 7.48 (d, J ¼ 7.2 Hz, 2H), 7.35–
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7.31 (m, 4H), 7.24–7.20 (m, 2H), 5.78 (s, 1H), 5.14 (s, 1H), 2.04 (s, 142.37, 140.9, 140.8, 140.2, 136.1, 131.9, 129.1, 128.8, 128.6,
3H); 13C NMR (100 MHz, CDCl3) d 197.6, 183.3, 143.6, 140.3, 128.3, 128.2, 127.9, 127.8, 127.4, 127.2, 126.1, 51.8, 19.9. HRMS
+
130.5, 128.4, 128.2, 128.0, 127.7, 126.2, 119.5, 113.2, 25.4 (mixed m/z calcd for C21H19O2 : 303.1385; found 303.1385.
with 3jb) (z-isomer).
Methyl 30,4,400-trimethyl-[1,10:40,100-terphenyl]-20-carboxylate
(Z)-1-Phenyl-2-(1-phenylethylidene)butane-1,3-dione5 (3jb). (5ba). White solid; yield of 5b 0.0613 g, 62%; 1H NMR (400 MHz,
Liquid; yield 0.0397 g, 50%; 1H NMR (400 MHz, CDCl3) d 7.70 (d, CDCl3) d 7.31 (d, J ¼ 8.0 Hz, 3H), 7.25 (m, 2H), 7.23 (d, J ¼ 4.4 Hz,
J ¼ 7.2 Hz, 2H), 7.38 (t, J ¼ 7.6 Hz, 1H), 7.28 (d, J ¼ 5.2 Hz, 1H), 4H), 7.20 (b, 1H), 3.64 (s, 3H), 2.41 (s, 3H), 2.39 (s, 3H), 2.25 (s,
7.23 (d, J ¼ 9.2 Hz, 1H), 7.09 (s, 5H), 2.47 (s, 3H), 2.27 (s, 3H); 13
C
3H); 13C NMR (100 MHz, CDCl3) d 170.8, 141.4, 138.6, 137.7,
NMR (100 MHz, CDCl3) d 198.6, 197.3, 151.2, 141.2, 139.7, 137.2, 137.1, 136.8, 134.1, 132.3, 130.9, 129.1, 129.0, 128.9, 128.1,
+
133.1, 129.2, 128.7, 128.3, 128.1, 127.7, 30.9, 22.5.
127.0, 51.9, 21.2, 21.1, 17.7. HRMS m/z calcd for C23H23O2 :
(E)-1-Phenyl-2-(1-phenylethylidene)butane-1,3-dione5 (3jb). 331.1698; found 331.1691.
Off white solid; 1H NMR (400 MHz, CDCl3) d 8.01 (d, J ¼ 8.0 Hz,
Methyl 4,400,50-trimethyl-[1,10:30,100-terphenyl]-40-carboxylate
1
2H), 7.61 (t, J ¼ 7.0 Hz, 1H), 7.52 (d, J ¼ 7.4 Hz, 2H), 7.43–7.41 (5bb). Yellow liquid; H NMR (400 MHz, CDCl3) d 7.50 (d, J ¼
(m, 3H), 7.35–7.33 (m, 2H), 2.05 (s, 3H), 1.87 (s, 3H); 13C NMR 8.0 Hz, 2H), 7.41 (s, 2H), 7.30 (d, J ¼ 8.0 Hz, 2H), 7.27 (m, 1H),
(100 MHz, CDCl3) d 200.5, 196.2, 148.1, 141.1, 140.8, 136.8, 7.22 (t, J ¼ 8.0 Hz, 3H), 3.62 (s, 3H), 2.45 (s, 3H), 2.39 (s, 3H), 2.38
133.8, 129.4, 129.0, 128.9, 128.8, 127.4, 30.8, 23.3.
(s, 3H); 13C NMR (100 MHz, CDCl3) d 170.5, 142.2, 140.6, 138.0,
3-Methyl-3-(1-phenylvinyl)pentane-2,4-dion2a,5 (3k). Yellow 137.6, 137.4, 137.1, 135.9, 129.5, 129.1, 128.1, 127.5, 127.1,
1
+
liquid; yield 0.0300 g, 46%; H NMR (500 MHz, CDCl3) d 7.31 125.9, 51.8, 21.2, 21.1, 19.9. HRMS m/z calcd for C23H23O2 :
(dd, J1 ¼ 1.6 Hz, J2 ¼ 4.8 Hz, 3H), 7.11 (d, J ¼ 7.6 Hz, 2H), 5.53 (s, 331.1698; found 331.1697.
1H), 5.24 (s, 1H), 2.29 (s, 6H), 1.38 (s, 3H); 13C NMR (100 MHz,
Methyl
4,400-diuoro-30-methyl-[1,10:40,100-terphenyl]-20-
1
CDCl3) d 207.7, 147.9, 139.7, 128.3, 127.9, 127.5, 119.7, 70.9, carboxylate (5ca). Off-white solid; yield of 5c 0.0557 g, 55%; H
27.3, 19.7.
NMR (400 MHz, CDCl3) d 7.39–7.35 (m, 2H), 7.30 (d, J ¼ 3.2 Hz,
2-Acetyl-2-(1-phenylvinyl)cyclopentanone2b (3l). Light yellow 1H), 7.28–7.27 (m, 2H), 7.23 (d, J ¼ 8.0 Hz, 1H), 7.15–7.08 (m,
solid; yield 0.0541 g, 79%; H NMR (400 MHz, CDCl3) d 7.32– 4H), 3.63 (s, 3H), 2.23 (s, 3H). 13C NMR (101 MHz, CDCl3)
1
7.28 (m, 3H), 7.16 (m, 2H), 5.58 (s, 1H), 5.43 (s, 1H), 2.76 (m, d 170.37, 162.4 (d, J ¼ 244 Hz), 162.2 (d, J ¼ 245 Hz), 140.8,
1H), 2.44–2.36 (m, 1H), 2.35 (s, 3H), 2.34–2.24 (m, 1H), 1.95–1.79 138.0, 136.9, 136.5, 134.4, 132.6, 130.9, 130.8 (d, J ¼ 8.0 Hz),
(m, 2H), 1.77–1.67 (m, 1H); 13C NMR (100 MHz, CDCl3) d 213.2, 129.9 (d, J ¼ 8.0 Hz) 127.09, 115.4 (d, J ¼ 8.0 Hz), 115.2 (d, J ¼ 9.0
205.1, 145.9, 139.4, 128.5, 128.0, 127.1, 118.8, 73.5, 38.4, 32.2, Hz), 52.05, 17.65. HRMS m/z calcd for C21H17F2O2+: 339.1196;
27.6, 18.6.
2-Acetyl-2-(1-(p-tolyl)vinyl)cyclopentanone (3m). Light yellow
found 339.1190.
Methyl
4,400-diuoro-50-methyl-[1,10:30,100-terphenyl]-40-
solid; yield 0.0495 g, 68%; 1H NMR (400 MHz, CDCl3) d 7.12 (d, J carboxylate (5cb). Viscous liquid; 1H NMR (400 MHz, CDCl3)
¼ 8.0 Hz, 2H), 7.06 (d, J ¼ 8.0 Hz, 2H), 5.56 (s, 1H), 5.37 (s, 1H), d 7.58–7.54 (m, 2H), 7.39–7.34 (m, 4H), 7.16–7.07 (m, 4H), 3.62
2.79–2.72 (m, 1H), 2.45–2.37 (m, 1H), 2.34 (s, 3H), 2.33 (s, 3H), (s, 3H), 2.46 (s, 3H); 13C NMR (100 MHz, CDCl3) d 170.0, 162.8
2.31–2.17 (m, 1H), 1.96–1.90 (m, 1H), 1.88–1.81 (m, 1H), 1.76– (d, J ¼ 246 Hz), 162.4 (d, J ¼ 246 Hz), 141.4, 139.8, 136.8 (d, J ¼
1.67 (m, 1H); 13C NMR (100 MHz, CDCl3) d 213.3, 205.3, 145.8, 3.0 Hz), 136.3, 136.2 (d, J ¼ 3.0 Hz), 132.1, 130.9, 130.8, 129.9 (d,
137.9, 136.5, 129.1, 126.9, 118.1, 73.6, 38.4, 32.2, 27.6, 21.0, 18.6. J ¼ 8.0 Hz), 128.8 (d, J ¼ 8.0 Hz), 127.8, 125.9, 115.8 (d, J ¼ 22
HRMS m/z calcd for C16H19O2+: 243.1385; found 243.1386.
2-Acetyl-2-(1-phenylvinyl)cyclohexanone2b,5 (3n). Light yellow
solid; yield 0.0517 g, 71%; 1H NMR (400 MHz, CDCl3) d 7.30 (dd,
Hz), 115.4 (d, J ¼ 21 Hz), 51.9, 19.9. HRMS m/z calcd for
21H17F2O2+: 339.1196; found 339.1198.
Methyl
30-methyl-4,400-bis(triuoromethyl)-[1,10:40,100-ter-
C
J ¼ 4.8, 1.6 Hz, 3H), 7.12 (dd, J ¼ 6.4, 2.8 Hz, 2H), 5.60 (s, 1H), phenyl]-20-carboxylate (5da). Off-white solid; yield of 5d
1
5.25 (s, 1H), 2.84–2.77 (m, 1H), 2.45–2.34 (m, 1H), 2.33 (s, 3H), 0.0683 g, 52%; H NMR (400 MHz, CDCl3) d 7.70 (dd, J ¼ 13.0,
2.19–2.14 (m, 1H), 2.10–2.04 (m, 1H), 1.93–1.88 (m, 1H), 1.78– 7.8 Hz, 4H), 7.53 (d, J ¼ 7.6 Hz, 2H), 7.45 (d, J ¼ 7.6 Hz, 2H), 7.34
1.71 (m, 1H), 1.51–1.47 (m, 2H); 13C NMR (100 MHz, CDCl3) (d, J ¼ 8.0 Hz, 2H), 7.30 (s, 4H), 3.63 (s, 3H), 2.25 (s, 3H); 13C
d 210.5, 208.0, 147.7, 139.7, 128.3, 127.8, 127.7, 121.6, 72.8, 40.4, NMR (100 MHz, CDCl3) d 169.9, 144.5, 144.0, 141.0, 138.2, 134.4,
33.1, 28.1, 27.6, 21.0.
132.8, 130.8, 129.6, 128.6, 127.1, 125.4 (t, J ¼ 3.5 Hz), 122.8, 96.1,
Methyl 30-methyl-[1,10;40,100-terphenyl]-20-carboxylate9 (5aa). 52.2, 17.7. HRMS m/z calcd for C23H16F6O2Na+: 461.0952; found
White solid; yield of 5a 0.0542 g, 60%; 1H NMR (400 MHz, 461.0955.
CDCl3) d 7.44–7.43 (m, 1H), 7.42–7.41 (m, 5H), 7.39–7.36 (m,
Methyl
50-methyl-4,400-bis(triuoromethyl)-[1,10:30,100-ter-
1H), 7.34–7.32 (m, 3H), 7.29–7.25 (m, 2H), 3.61 (s, 3H), 2.26 (s, phenyl]-40-carboxylate (5db). Viscous liquid; 1H NMR (400 MHz,
3H); 13C NMR (100 MHz, CDCl3) d 170.6, 141.7, 141.1, 140.6, CDCl3) d 7.71 (s, 4H), 7.69 (d, J ¼ 8.0 Hz, 2H), 7.54–7.50 (m, 3H),
138.9, 134.2, 132.4, 130.9, 129.3, 128.8, 128.4, 128.3, 128.2, 7.42 (b, 1H), 3.63 (s, 3H), 2.50 (s, 3H); 13C NMR (100 MHz,
127.4, 127.3, 127.2, 127.1, 51.9, 17.7. HRMS m/z calcd for CDCl3) d 169.5, 144.2, 143.4, 141.1, 139.6, 136.8, 132.7, 130.2,
+
C
21H19O2 : 303.1385; found 303.1383.
129.9 (d, J ¼ 11 Hz), 129.6 (d, J ¼ 9 Hz), 128.7, 128.6, 127.5,
Methyl 50-methyl-[1,10;30,100-terphenyl]-40-carboxylate17 (5ab). 126.1, 125.8 (d, J ¼ 3 Hz), 125.4 (t, J ¼ 6.5 Hz), 122.8, 52.1, 19.9.
Viscous liquid; 1H NMR (400 MHz, CDCl3) d 7.62 (d, J ¼ 7.6 Hz, HRMS m/z calcd for C23H17F6O2+: 439.1132; found 437.2268* (*
2H), 7.46–7.44 (m, 4H), 7.42–7.41 (m, 4H), 7.37–7.32 (m, 2H), HRMS has been recorded two times, but we obtained the same
3.60 (s, 3H), 2.48 (s, 3H); 13C NMR (100 MHz, CDCl3) d 170.2,
36018 | RSC Adv., 2020, 10, 36014–36019
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mass, 437.2268. The compound probably undergoes
fragmentation.)
Notes and references
Ethyl 30-methyl-[1,10:40,100-terphenyl]-20-carboxylate9 (5ea).
White solid; yield of 5e 0.0591 g, 62%; 1H NMR (400 MHz,
CDCl3) d 7.45–7.42 (m, 5H), 7.40–7.37 (m, 2H), 7.34–7.32 (m,
3H), 7.28–7.25 (m, 2H), 4.09 (q, J ¼ 7.2 Hz, 2H), 2.28 (s, 3H), 0.99
(t, J ¼ 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) d 170.0, 141.7,
141.2, 140.7, 139.0, 134.4, 132.4, 130.8, 129.3, 128.4, 128.3,
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128.2, 127.4, 127.1, 127.0, 61.0, 17.6, 13.7. HRMS m/z calcd for
+
C
22H21O2 : 317.1541; found 317.1542.
Ethyl 50-methyl-[1,10:30,100-terphenyl]-40-carboxylate (5eb).
1
Liquid; H NMR (400 MHz, CDCl3) d 7.61 (d, J ¼ 8.8 Hz, 2H),
7.46–7.44 (m, 4H), 7.41–7.38 (m, 4H), 7.37 (b, 1H), 7.35–7.32 (m,
1H), 4.07 (q, J ¼ 7.0 Hz, 2H), 2.49 (s, 3H), 0.96 (t, J ¼ 7.0 Hz, 3H);
13C NMR (100 MHz, CDCl3) d 169.7, 142.2, 141.1, 140.9, 140.31,
136.1, 132.1, 128.8, 128.4, 128.2, 127.9, 127.7, 127.4, 127.2,
6 B. Leotard, T. Fukuyama, Y. Higashibeppu, C. Brancour,
H. Okamoto and I. Ryu, Synlett, 2013, 24, 2287.
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X. Shi, Org. Lett., 2014, 16, 306.
+
126.2, 60.9, 19.9, 13.6. HRMS m/z calcd for C22H21O2 : 317.1541;
found 317.1540.
Ethyl
30,4,400-trimethyl-[1,10:40,100-terphenyl]-20-carboxylate
(5fa). White solid; yield of 5f 0.0710 g, 69%; 1H NMR (400 MHz,
CDCl3) d 7.30 (t, J ¼ 6.8 Hz, 3H), 7.26–7.25 (m, 2H), 7.23 (d, J ¼
2.5 Hz, 3H), 7.20 (d, J ¼ 7.6 Hz, 2H), 4.11 (q, J ¼ 7.2 Hz, 2H), 2.41
(s, 3H), 2.39 (s, 3H), 2.26 (s, 3H), 1.04 (t, J ¼ 7.2 Hz, 3H); 13C
NMR (100 MHz, CDCl3) d 170.1, 141.4, 138.7, 138.32, 137.8,
137.0, 136.7, 134.4, 132.3, 130.8, 129.2, 128.9, 128.9, 128.3,
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2901; (b) D. B. Grotjahn, in Comprehensive Organometallic
Chemistry II, Ed. L. S. Hegedus, E. W. Abel, F. G. A. Stone
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171–197.
+
127.0, 60.9, 21.2, 21.1, 17.6, 13.7. HRMS m/z calcd for C24H25O2 :
345.1854; found 345.1852.
Ethyl
4,400,50-trimethyl-[1,10:30,100-terphenyl]-40-carboxylate
1
(5). Liquid; H NMR (400 MHz, CDCl3) d 7.50 (d, J ¼ 8.0 Hz,
2H), 7.41 (s, 2H), 7.31 (d, J ¼ 8.0 Hz, 2H), 7.24–7.12 (m, 4H), 4.10
(q, J ¼ 7.2 Hz, 2H), 2.46 (s, 3H), 2.39 (s, 3H), 2.38 (s, 3H), 1.01 (t, J
¼ 7.0 Hz, 3H); 13C NMR (101 MHz, CDCl3) d 169.8, 142.1, 140.7,
138.1, 137.6, 137.4, 137.1, 135.9, 129.5, 128.9, 128.2, 127.5,
127.0, 125.9, 60.9, 21.2, 21.1, 19.9, 13.7. HRMS m/z calcd for
+
C
24H25O2 : 345.1854; found 345.1853.
Conflicts of interest
There are no conicts to declare.
15 (a) K. Tanaka, K. Tyoda, A. Wada, K. Shiraska and M. Hirano,
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K.-i. Kanno, Q. Guo, B. Shen and T. Takahashi, Org. Lett.,
2009, 11, 3318.
Acknowledgements
We thank SERB for the NMR facility (Grant Number SR/FST/
CSII-026/2013).
´
´
16 D. G. Yu, T. Gensch, F. De Azambuja, S. Vasquez-Cespedes
and F. Glorius, J. Am. Chem. Soc., 2014, 136, 17722.
17 T. Zhu, P. Zheng, C. Mou, S. Yang, B.-A. Song and Y. R. Chi,
Nat. Commun., 2014, 5, 5027.
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