A Suzuki-type cross-coupling reaction of arylacetylene halides with arylboronic acids

Article abstract of DOI:10.1002/aoc.1795

A PdCl₂-catalyzed direct alkynylation of arylboronic acids to give diarylacetylenes is described. The optimal conditions using PdCl ₂ as catalyst, MeOH-PhMe-H₂O as solvent and K ₂CO₃ as base effectively suppressed the formation of homo-coupling product and afforded moderate to good yield of the desired unsymmetrical coupling product. This reaction represents a Suzuki-type sp ²(C-B)-sp(C-X) cross-coupling. Copyright

Full text of DOI:10.1002/aoc.1795

Full Paper
Received: 1 December 2010
Revised: 19 February 2011
Accepted: 19 February 2011
Published online in Wiley Online Library: 26 April 2011
(wileyonlinelibrary.com) DOI 10.1002/aoc.1795
A Suzuki-type cross-coupling reaction of
arylacetylene halides with arylboronic acids
Yu Shia, Xiaoyu Lib, Jianhui Liua∗, Wenfeng Jiangc and Licheng Suna,d
A PdCl2-catalyzed direct alkynylation of arylboronic acids to give diarylacetylenes is described. The optimal conditions using
PdCl2 as catalyst, MeOH–PhMe–H2O as solvent and K2CO3 as base effectively suppressed the formation of homo-coupling
product and afforded moderate to good yield of the desired unsymmetrical coupling product. This reaction represents a
2
c
Suzuki-type sp (C–B)–sp(C–X) cross-coupling. Copyright ꢀ 2011 John Wiley & Sons, Ltd.
Supporting information may be found in the online version of this article.
Keywords: Suzuki cross-coupling; diarylacetylene; palladium chloride; alkynylation
Introduction
organometallics renders the process uneconomical. In a previous
communication,[12] we reported a new approach to the synthe-
sis of diarylacetylenes by the coupling of arylacetylene iodides
and arylboronic acids. We have since extended this reaction to
arylacetylene bromides and here disclose this type of Suzuki
cross-coupling (sp2 –sp) from haloalkynes (iodo and bromo) and
arylboronic acids to form diarylacetylenes, and describe further
details on the process.
The palladium-catalyzed Suzuki cross-coupling reaction between
different types of organoboron compounds and organic halides or
triflates provides a powerful and useful synthetic methodology for
theformationofcarbon–carbonbonds. Thenewprotocolsrelated
to this cross-coupling reaction have been reported continuously
since its discovery. Originally, sp2 –sp2 C–C coupling leading to
the diaryl compounds dominated Suzuki coupling. Later on, the
scope of the Suzuki reaction was extended, and recently its ability
to couple aryl or alkyl boron compounds with sp3-hybridized
alkyl halides to form sp2 –sp3 and sp3 –sp3 C–C bonds has been
extensively explored.[1] Generally, the organoboron compounds
could be (hetero)aryl, alkenyl, alkyl and even alkynylboronic
acid, but the choice of the electrophilic partner was limited to
(hetero)aryl, vinylic and alkyl halides. The employment of alkynyl
iodide in the coupling reaction was a great challenge because of
the cross-homo scrambling, and there have been no reports on
this kind of coupling reaction. There have been few reports on the
sp2 –sp C–C bond formation by coupling of sp C–X bonds and
sp2 C–B bonds[2] compared with sp2 or sp3 C–X (X = halogen)
substrates employed to couple with organoboron derivatives.
In recent years, diarylacetylenes have received a great
deal of attention owing to their spectroscopic and electronic
properties[3] as well as their biological activities.[4] In addition
to the traditional elimination and alkylation reactions, there
are many other approaches to synthesize diarylacetylenes, such
as alkyne metathesis,[5] Seyferth–Gilbert homologation[6] and
Castro–Stephens coupling.[7] The most direct and powerful
synthetic strategies for the diarylacetylenes formation is the
Sonogashira coupling reaction,[8] which is a Pd-catalyzed cross
coupling of an aryl halide with a terminal acetylene. However,
this method has some limitations,[9] for example, giving low
yields or requiring high reaction temperatures in some cases.
Therefore, alternative Pd-catalyzed alkynylation protocols have
been established. For instance, besides the well-known Negishi
cross-coupling reactions,[10] the alkynyltrifluoroborate reagents[9]
developed by Molander and alkynyldimethylalminum reagents
by Micouin[11] provide other strategies for the sp2 –sp C–C bond
formations. However, the requirement for substrate activation by
Results and Discussion
This study originated from our past work on polysubstituted
pyrroles, which has been described in a previous paper.[13] Pyrrole
3wasoneofthetargetmoleculesofthe2,3,4-trisubstitutedpyrrole
1 (Scheme 1). Originally, we attributed the value at δ 0.33 to the
1
TMS(trimethylsilyl) attached to the triple bond bases on the H
NMR. It seems that the trimethylsilyl group on C-3 of pyrrole 1 was
replaced by the p-methoxyphenyl to form 3 through iodination
and subsequent Suzuki cross-coupling reaction. However, further
study revealed that this structural assignment was incorrect. The
correct structure was established by X-ray crystallography and
designated as compound 5. Our analysis displayed iodination and
subsequent coupling took place, but iodination occurred on the
∗
Correspondence to: Jianhui Liu, State Key Laboratory of Fine Chemicals, DUT-
KTH Joint Education and Research Center on Molecular Devices, Dalian
University of Technology, Dalian 116012, People’s Republic of China.
E-mail: liujh@dlut.edu.cn
a
StateKeyLaboratoryofFineChemicals, DUT-KTHJointEducationandResearch
Center on Molecular Devices, Dalian University of Technology, Dalian 116012,
People’s Republic of China
b
c
DalianHissenBio-Pharm.Co.Ltd,No.17TieshanWestRd,DalianEconomicand
Technological Development Zone, Dalian 116600, People’s Republic of China
Department of Chemistry, Dalian University of Technology, Dalian 110024,
People’s Republic of China
d
Department of Chemistry, Royal Institute of Technology, 10044 Stockholm,
Sweden
c
Appl. Organometal. Chem. 2011, 25, 514–520
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A Suzuki-type cross-coupling reaction
Scheme 1. The transformation from pyrrole 1 to pyrrole3.
with substituted groups in the pyrrole: 359.8(5)◦, 359.7(5)◦ and
359.9(5)◦, respectively. However, the S1 atom is out of the plane
of the pyrrole ring with the sum of the angles around N1 being
316.5(4)◦. Thephenylandthepyrrolylgroupsareco-linearbecause
of the rigidity of the connecting ethynyl group, and the rings are
approximately orthogonal to each other.
Based on this unexpected result, we were interested to see
if other substrates could be applied under the same conditions:
Pd(PPh3)4, Na2CO3, MeOH(methanol)–PhMe(toluene)–H2O and
reflux. Different substrates were tried under this catalytic system,
but the yield of cross-coupling products was not satisfactory. We
began to explore the conditions to optimize the reaction by using
(p-methoxycarbonylphenyl)ethynyl iodide and p-methylphenyl
boronic acid as reaction partners in the reaction (Scheme 2).
We modified the reaction conditions with respect to four key
variables: the catalyst system, the solvent system, the base
and the amount of substrates. Of the different palladium
catalysts examined, including Pd(PPh3)4, Pd(PPh3)2Cl2, Pd(OAc)2
and PdCl2, the best result was obtained using PdCl2 (1 mol%).
The most suitable solvent system for this transformation was the
typical solvent mixture widely used in Suzuki coupling reaction:
MeOH–toluene–H2O (3 : 3:1). The solvents MeOH, THF(tetra hydro
furan) and THF–water were found to be less effective. Usually,
when the reaction proceeded in a weak polar solvent with Pd0
complex as catalyst, the major product would be the homo-
coupling product of the arylacetylene iodides. When the PdII
complex catalyst was added, homo-coupling of arylboronic acids
predominated. All of the organic and inorganic bases, K2CO3,
CH3ONa, NaOH, Et3N and K3PO4, gave good yields. The amount
of p-methylphenylboronic acid is crucial, and when it was raised
to 1.5 equiv., the yield of the coupling products was substantially
increased by circumventing homo-dimerization from arylboronic
acid. A greater amount of boronic acid (2 or 3 equiv.) did
not improve the yield. Thus, the best result (yield of 88%)
Figure 1. Molecular structure of pyrrole 5 drawn at the 30% probability
level with ORTEP-3.[14]
.
TMS attached to the triple bond with the result of a new kind
of coupling reaction between alkynyl iodide and phenylboronic
acid, which has not been systematically studied before. Selective
iodination and arylboronic acid coupling with the iodide on the sp
carbon atom are two significant features for this transformation.
As far as we know, this is the first case of a 1-iodo-2-arylalkyne
coupling with arylboronic acid to form a diarylacetylene under
Suzuki-type conditions.
From the single crystal X-ray diffraction structure of 5 (Fig. 1),
which was drawn with 30% displacement ellipsoids using ORTEP-
3,[14] we can see that the atoms adjacent to the pyrrole (C5,
C17 and Si1) are in the plane of the pyrrole ring, which is
confirmed by the sum of the angles around the carbon atoms
Scheme 2. The optimized conditions to couple arylacetylene iodides with arylboronic acids.
c
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Y. Shi et al.
was obtained when PdCl2 (1 mol%) was employed as catalyst,
MeOH–toluene–H2O (3 : 3:1) as solvent, K2CO3 (2 M) as base, and
1.5 equiv. p-methylphenylboronic acid with refluxing at 80 ◦C for
8 h.
or 2,4,6-trichloroboronic acid as reactants while keeping electron-
withdrawing substituents on the phenyl ring of the alkynyl
bromide, acceptable yields were obtained (entries 9–11). Usually,
the yields of cross-coupling products were almost the same as that
of the iodide analogue (Table 1). Different arylacetylene bromides
with electron-withdrawing groups on the phenyl or heterocyclic
subunit reacted smoothly with 1.5 equiv. p-methylphenylboronic
acid (Table 2, entries 1–7). However, when arylacetylene bromides
containing electron-rich substrates were used, the reactions did
not proceed even with 5 mol% catalyst in 24 h (entries 12 and 13).
In most cases the yields obtained from the protocol outlined in
this paper are comparable to those obtained by the Sonogashira
reaction;[15] however, in some cases the yields from our protocol
are superior. One example involved the reaction of 4-(2-
iodoethynyl)benzaldehyde with p-methylphenylboronic acid for
the preparation of 4-[2-(4-methylphenyl)ethynyl] benzaldehyde
(entry 2 in Tables 1 and 2). Much improved yields (84 and 83%
respectively) were achieved compared with the result (31%)
obtained by ordinary Sonogashira coupling.[16] Although a high
yield of this product was recently reported by Sonogashira
coupling, an unusual N-heterocyclic carbene precatalyst was
required, which has a complicated structure and requires a multi-
step synthesis.[17] Some other -CHO group-containing products
were also prepared in good to high yields, the results indicating
that -CHO group can facilitate the cross coupling reaction in this
system. In the Sonogashira reaction, the acetylene subunit of the
diarylacetylene comes from the nucleophile, whereas with our
method the acetylene subunit comes from the electrophile. The
change of the acetylene subunit from nucleophile to electrophile
makes this method a supplement of the Sonogashira reaction to
synthesize diarylacetylenes.
Under the optimal conditions, the experimental scope was
extended to other arylacetylene iodides and arylboronic acids
(Table 1). The aryl subunit on arylethynyl iodide can tolerate
differenttypesofsubstituents:phenylringswithelectron-deficient
groups such as para-substituted -CO2Me, -CHO, -COMe and -CN,
and ortho-substituted -CF3 gave good to high yields (83–92%,
entries 1–5); phenyl rings containing electron-rich substituents
such as para-Me and -OMe also reacted well, giving yields of 82
and 79%, respectively (entries 7 and 8), but they were not as
reactive as the electron-deficient substrates and more catalyst
(5 mol%) was needed. When iodoethynyl-benzene was employed,
the yield was 74% (entry 6). Ortho-substituted arylethynyl iodides
were used with good results, with ortho-CF3 and -CHO groups
affording yields of 83 and 82%, respectively (entries 5 and
12). Replacing the aryl group of an arylacetylene iodide with a
heteroaryl gave satisfactory results. For example, furan, thiophene
and benzo[1,3]dioxole-containing substrates bearing electron-
withdrawing groups (-CHO, -COOMe) gave yields ranging from 82
to 91% (entries 9–12). These heterocyclic cross coupling products
are new compounds which have not been reported before.
Pyridine-containing arylacetylene iodides were not employed in
thereactionbecauseoftheirsensitivitytolightandheatduringthe
preparation. When a variety of substituted phenylboronic acids
such as naphthyl, 4-methoxyphenyl, 2-hydroxyphenyl, phenyl, 4-
fluorophenyl and 2,4,6-trichloro-phenylboronic acid were used
as the substrate (entries 13–19), a lower yield was observed
with the bulky naphthyl boronic acid (69%, entry 13), but
acceptable to good yields were obtained not only for electron-
rich borolanes bearing -OMe and -OH (entries 14–16), and for
electronically neutral phenylboronic acid (entry 17), but also
for electron-poor systems with F and Cl (entries 18 and 19).
However, with substituents in the ortho position of the aryl
rings, the reactants showed relatively less activity because of
steric hindrance (entries 16 and 19). With the p-fluorophenyl and
2,4,6-trichlorophenylboronic acids, the reaction gave inseparable
mixtures consisting of both cross-coupling and homo-coupling
products, the latter being a minor by-product which has the same
Rf value as the desired cross-coupling product. Thus, the yields
are given based on the 1H NMR spectra. We can see that this
catalytic system allows a diverse range of electron density around
the aromatic rings either from arylacetylene iodides or aryl boronic
acids.
Conclusion
We have established a new protocol for the preparation of
diarylacetylenes, and demonstrated the ability of sp–C halides
to couple with sp2 –C boronic acids. This is an important addition
to the well-known Suzuki cross-coupling reaction. This process
offers broad scope with respect to both the alkynyl halides and
arylboronic acids by allowing a wide range of electron density on
the aromatic rings. The change of the arylacetylene subunit from
nucleophile to electrophile makes this method a supplement to
the Sonogashira reaction.
Experimental Section
We were curious whether these optimized conditions could
be applied to brominated terminal alkynes. The reactions of p-
methylphenyl boronic acid with arylacetylene bromides were
first examined. The results are shown in Table 2. The reaction of
arylacetylene bromides with 1.5 equiv. of p-methylphenylboronic
acid gave the desired coupling product (entry 1). Similarly, p-
CHO, p-COMe, and p-CN substituted phenyl analogs gave the
expected products in comparable yields (entries 2–4). However,
when the electron-withdrawing -CF3 group was in the ortho
position on the phenyl ring, the yield decreased slightly (entry 5).
Heterocyclic systems were also investigated. Thiophene and furan
rings containing electron-withdrawing groups -CHO and -COMe
underwent smooth transformation in good yields (entries 6 and
7). Next, we investigated different boronic acids. Employment of
2-naphthylboronicacidledtomarkedlyreducedyieldowingtothe
steric hindrance (entry 8). When we used the less reactive p-fluoro
All arylacetylene iodides,[18] arylacetylene bromides[19] and some
arylboronic acids[20] were prepared according to literature
procedures. All of the compounds synthesized were characterized
by 1H, 13C NMR and mass spectrometry.
General Procedure for the Synthesis of the Diarylacetylenes
Haloethynyl aryl substrate (0.2 mmol), arylboronic acid (0.3 mmol),
PdCl2 (0.35 mg, 0.002 mmol) and K2CO3 (55.2 mg, 0.4 mmol) were
added to a solution of 7 ml MeOH–toluene–H2O (3 : 3:1). The
resulting mixture was stirred and heated at ca. 80 ◦C for 8 h and
then cooled to room temperature. The mixture was extracted with
Et2O (2 × 20 ml), washed with H2O (15 ml), dried (Na2SO4), filtered
and evaporated, and the residue was purified by chromatography
on silica gel to give the cross coupling product as crystals.
c
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A Suzuki-type cross-coupling reaction
Table 1. Coupling of arylacetylene iodides and arylboronic acids
Entry
1
Ar1
Ar2
Isolated yield (%)
88
2
3
4
5
84a
92
85a
83b
6
74b,c
82d
79d
91
7
8
9
10
11
12
86
89
82
13
69
14
15
16
82
84
73
17
18
19
78
84
79b
a The solvent was THF–MeOH–H2O. b Yield determined by 1H NMR. c The catalyst amount was 2.5 mol%. d The catalyst amount was 5 mol%.
4-[2-(4-Methylphenyl)ethynyl]benzoic Acid Methyl Ester
166.8 (CO). GC/TOF HRMS-EI: calcd for C13H14O2, 250.0994; found
250.0993.
Yield 44 mg, 88%; pale-yellow crystals, m.p.: 134–136 ◦C. 1H NMR
(CDCl3) δ 2.37 (s, 3H, CH3), 3.92 (s, 3H, CH3), 7.17 (d, J = 8 Hz,
2H, CH), 7.44 (d, J = 8 Hz, 2H, CH), 7.57 (d, J = 8.4 Hz, 2H,
CH), 8.01 (d, J = 8.4 Hz, 2H, CH). 13C NMR (CDCl3) δ 21.7 (CH3),
52.4 (CH3), 88.2 (C C), 92.8 (C C), 119.8 (aromatic C), 128.4
(aromaticC), 129.4(aromaticC), 129.6(aromaticC), 129.7(aromatic
C), 131.6 (aromatic C), 131.8 (aromatic C), 139.2 (aromatic C),
4-[2-(4-Methylphenyl)ethynyl]benzaldehyde
White crystals, m.p.: 118–123 ◦C. 1H NMR (CDCl3) δ 2.41 (s, 3H,
CH3), 7.28 (d, J = 8.4 Hz, 2H, CH), 7.53 (d, J = 8 Hz, 2H, CH),
7.73 (d, J = 8 Hz, 2H, CH), 7.92 (d, J = 8.4 Hz, 2H, CH), 10.05
(s, 1H, CHO). 13C NMR (CDCl3) δ 21.3 (CH3), 127.4 (aromatic C),
c
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Table 2. Coupling of arylacetylene bromides and arylboronic acids
Entry
1
Ar1
Ar2
Isolated yield (%)
85
2
3
4
5
83
88
85
76a
6
7
8
82
84
49
9
71
10
69a
11
12
13
78
0
0
a Yield determined by 1H NMR.
127.6 (aromatic C), 129.9 (aromatic C), 130.4 (aromatic C), 135.1
C), 119.3 (aromatic C), 128.7 (aromatic C), 129.5 (aromatic C), 131.9
(aromaticC), 132.2(aromaticC), 132.2(aromaticC), 139.6(aromatic
C). GC/TOF HRMS-EI: calcd for C16H11N, 217.0891; found 217.0882.
(aromaticC), 136.9(aromaticC), 138.7(aromaticC), 147.3(aromatic
C), 192.1 (CHO). GC/TOF HRMS-EI: calcd for C16H12O, 220.0888;
found 220.0894.
2-[2-(4-Methylphenyl)ethynyl]benzotrifluoride
1-{4-[2-(4-Methylphenyl)ethynyl]phenyl}ethanone
◦
1
Yellow crystals, m.p.: 130–132 C. H NMR (CDCl3) δ 2.38 (s, 3H,
CH3), 2.62 (s, 3H, CH3), 7.18 (d, J = 8 Hz, 2H, CH), 7.48 (d, J = 8 Hz,
2H, CH), 7.60 (d, J = 8.4 Hz, 2H, CH), 7.94 (d, J = 8.4 Hz, 2H, CH). 13C
NMR (CDCl3) δ 21.7 (CH3), 26.8 (CH3), 88.2 (C C), 93.2 (C C), 119.7
(aromaticC), 128.4(aromaticC), 128.6(aromaticC), 129.4(aromatic
C), 131.8 (aromatic C), 131.8 (aromatic C), 136.2 (aromatic C), 139.3
(aromatic C), 197.5 (CN). API-ES: calcd for C17H14O, 234.1045; found
235.2 [M + H]+.
Mixure of the product and 4,4ꢁ-dimethyl-biphenyl, white crystals,
1H NMR (CDCl3) δ 2.38 (s, 3H, CH3), 7.16 (d, J = 8 Hz, 2H, CH), 7.38
(t, J = 7.6 Hz, 1H, CH), 7.47 (d, J = 8 Hz, 2H, CH), 7.49 (t, J = 8 Hz,
1H, CH), 7.64 (d, J = 8.8 Hz, 1H, CH), 7.66 (d, J = 8.4 Hz, 1H, CH).
GC/TOF HRMS-EI: calcd for C16H11F3, 260.0813; found 260.0822.
1-Methyl-4-phenylethynylbenzene
Because of the difficulties in separation, we only obtained the
mixture of the product and the byproduct 4,4ꢁ-dimethyl-biphenyl.
1H NMR (CDCl3) δ 2.38 (s, 3H, CH3), 7.15(d, J = 8 Hz, 2H, CH),
7.31–7.36 (m, 3H, Ph), 7.47 (d, J = 8.4 Hz, 2H, CH), 7.52 (d,
J = 8.4 Hz, 2H, CH). GC/TOF HRMS-EI: calcd for C15H12,192.0939;
found 192.0948.
4-[2-(4-Methylphenyl)ethynyl]benzonitrile
◦
1
Yellow crystals, m.p.: 162–164 C. H NMR (CDCl3) δ 2.38 (s, 3H,
CH3), 7.18 (d, J = 8 Hz, 2H, CH), 7.43 (d, J = 8 Hz, 2H, CH), 7.58 (d,
J = 8.4 Hz, 2H, CH), 7.62 (d, J = 8.4 Hz, 2H, CH). 13C NMR (CDCl3)
δ 21.8 (CH3), 87.4 (C C), 94.3 (C C), 111.4 (CN), 118.8 (aromatic
c
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A Suzuki-type cross-coupling reaction
1-{4-[2-(4-Methylphenyl)ethynyl]phenyl}methyl Ether
125.4 (aromatic C), 126.2 (aromatic C), 126.7 (aromatic C), 127.1
(aromaticC), 128.3(aromaticC), 128.5(aromaticC), 129.5(aromatic
C), 129.7 (aromatic C), 129.7 (aromatic C), 130.9 (aromatic C), 131.7
(aromatic C), 133.4 (aromatic C), 166.7 (CO). GC/TOF HRMS-EI: calcd
for C20H14O2, 286.0994; found 286.1000.
Pale-yellowcrystals,m.p.:120–124 ◦C.1HNMR(CDCl3)δ 2.36(s,3H,
CH3), 3.82 (s, 3H, CH3), 6.87 (d, J = 8.8 Hz, 2H, CH), 7.14 (d, J = 8 Hz,
2H, CH), 7.40 (d, J = 8 Hz, 2H, CH), 7.46 (d, J = 8.8 Hz, 2H, CH).
13C NMR (CDCl3) δ 21.7 (CH3), 55.5 (CH3), 88.4 (C C), 88.9 (C C),
114.2 (aromatic C), 115.8 (aromatic C), 120.7 (aromatic C), 129.3
(aromaticC), 131.5(aromaticC), 133.2(aromaticC), 138.2(aromatic
C), 159.7 (aromatic C). API-ES: calcd for C16H14O, 222.1045; found
223.1 [M + H]+.
4-(4-Methoxyphenylethynyl)benzoic Acid Methyl Ester
◦
1
Pale-yellow crystals, m.p.: 156–158 C. H NMR (CDCl3) δ 3.83 (s,
3H, CH3), 3.92 (s, 3H, CH3), 6.89 (d, J = 8.8 Hz, 2H, CH), 7.48 (d,
J = 8.8 Hz, 2H, CH), 7.56 (d, J = 8 Hz, 2H, CH), 8.00 (d, J = 8.4 Hz,
2H, CH). 13C NMR (CDCl3) δ 52.3 (CH3), 55.5 (CH3), 87.7 (C C),
92.7 (C C), 114.3 (aromatic C), 114.9 (aromatic C), 128.6 (aromatic
C), 129.3 (aromatic C), 129.6 (aromatic C), 131.4 (aromatic C),
133.4 (aromatic C), 160.2 (aromatic C), 166.8 (CO). API-ES: calcd for
C17H14O3, 266.0943; found 267.4 [M + H]+.
5-p-Tolylethynyl-thiophene-2-carbaldehyde
Yellow crystals, m.p.: 136–138 ◦C. 1H NMR (acetone-d6) δ 2.38 (s,
3H, CH3), 7.28 (d, J = 8 Hz, 2H, CH), 7.47 (d, J = 3.6 Hz, 1H, CH), 7.48
(d, J = 8 Hz, 2H, CH), 7.94 (d, J = 4 Hz, 1H, CH), 9.95 (s, 1H, CHO).
13C NMR (acetone-d6) δ 20.6 (CH3), 81.0 (C C), 97.9 (C C), 118.7
(aromaticC), 129.4(aromaticC), 131.5(aromaticC), 131.5(aromatic
C), 133.0 (aromatic C), 137.0 (aromatic C), 140.0 (aromatic C), 144.3
(aromatic C), 182.8 (CHO). GC/TOF HRMS-EI: calcd for C14H10OS,
226.0452; found 226.0459.
1-[4-(4-Methoxyphenylethynyl)-phenyl]ethanone
◦
1
Yellow crystals, m.p.: 128–131 C. H NMR (CDCl3) δ 2.61 (s, 3H,
CH3), 3.84 (s, 3H, CH3), 6.90 (d, J = 9.2 Hz, 2H, CH), 7.49 (d,
J = 8.8 Hz, 2H, CH), 7.58 (d, J = 8.4 Hz, 2H, CH), 7.93 (d, J = 8.4 Hz,
2H, CH). 13C NMR (CDCl3) δ 26.5 (CH3), 55.3 (CH3), 87.5 (C C),
92.9 (C C), 114.1 (aromatic C), 114.7 (aromatic C), 128.2 (aromatic
C), 128.6 (aromatic C), 131.4 (aromatic C), 133.2 (aromatic C),
135.9 (aromatic C), 160.1 (aromatic C), 197.3 (CO). API-ES: calcd for
C17H14O2, 250.0994; found 251.1 [M + H]+.
5-p-Tolylethynyl-furan-2-carbaldehyde
Yellow crystals, m.p.: 97–100 ◦C. 1H NMR (CDCl3) δ 2.39 (s, 3H, CH3),
6.75 (d, J = 3.6 Hz, 1H, CH), 7.19 (d, J = 7.6 Hz, 2H, CH), 7.25 (d,
J = 4 Hz, 1H, CH), 7.44 (d, J = 8 Hz, 2H, CH), 9.63 (s, 1H, CHO). 13C
NMR (CDCl3) δ 21.6 (CH3), 78.0 (C C), 96.8 (C C), 116.7 (aromatic
C), 118.1 (aromatic C), 129.3 (aromatic C), 131.7 (aromatic C), 140.1
(aromatic C), 142.3 (aromatic C), 152.3 (aromatic C), 177.2 (CHO).
API-ES: calcd for C14H10O2, 210.0681; found 211.1 [M + H]+.
1-[4-(2-Hydroxyphenylethynyl)phenyl]ethanone
◦
1
Pale-yellow crystals, m.p.: 170–175 C. H NMR (CDCl3) δ 2.63 (s,
3H, CH3), 7.26 (t, J = 7.2 Hz, 1H, CH), 7.33 (t, J = 8 Hz, 1H, CH),
7.54 (d, J = 8 Hz, 1H, CH), 7.61 (d, J = 7.6 Hz, 1H, CH), 7.94
(d, J = 8.4 Hz, 2H, CH), 8.03 (d, J = 8.4 Hz, 2H, CH). 13C NMR
(CDCl3) δ 26.8 (CH3), 103.8 (C C), 111.5 (C C), 121.5 (aromatic
C), 123.4 (aromatic C), 124.9 (aromatic C), 125.3 (aromatic C), 129.0
(aromaticC), 129.1(aromaticC), 134.7(aromaticC), 136.7(aromatic
C), 154.7 (aromatic C), 155.4 (aromatic C), 197.5 (CO). API-ES: calcd
for C16H12O2, 236.0837; found 237.1 [M + H]+.
5-p-Tolylethynyl-furan-2-carboxylic Acid Methyl Ester
◦
1
Yellow crystals, m.p.: 105–107 C. H NMR (CDCl3) δ 2.38 (s, 3H,
CH3), 3.92 (s, 3H, CH3), 6.67 (d, J = 3.6 Hz, 1H, CH), 7.17 (d,
J = 7.6 Hz, 2H, CH), 7.19 (d, J = 3.6 Hz, 1H, CH), 7.43 (d, J = 8 Hz,
2H, CH). 13C NMR (CDCl3) δ 21.6 (CH3), 52.1 (CH3), 78.0 (C C),
95.3 (C C), 116.2 (aromatic C), 118.4 (aromatic C), 118.9 (aromatic
C), 129.3 (aromatic C), 131.6 (aromatic C), 139.7 (aromatic C),
140.6 (aromatic C), 144.2 (aromatic C), 158.5 (CO). API-ES: calcd for
C15H12O3, 240.0786; found 241.1 [M + H]+.
1-(4-Phenylethynyl-phenyl)ethanone
Pale-yellow crystals, m.p.: 95–98 ◦C. 1H NMR (CDCl3) δ 2.60 (s,
3H, CH3), 7.35–7.37 (m, 3H, Ph), 7.54–7.56 (m, 2H, Ph), 7.60 (d,
J = 8.4 Hz, 2H, CH), 7.93 (d, J = 8.4 Hz, 2H, CH). 13C NMR (CDCl3)
δ 26.7 (CH3), 88.7 (C C), 92.9 (C C), 122.8 (aromatic C), 128.3
(aromaticC), 128.4(aromaticC), 128.6(aromaticC), 128.9(aromatic
C), 131.8 (aromatic C), 131.9 (aromatic C), 136.3 (aromatic C), 197.4
(CO). API-ES: calcd for C16H12O2, 220.0888; found 221.1 [M + H]+.
6-p-Tolylethynyl-benzo[1,3]dioxole-5-carbaldehyde
◦
1
Yellow crystals, m.p.: 145–148 C. H NMR (CDCl3) δ 2.38 (s, 3H,
CH3), 6.07 (s, 2H, CH2), 7.00 (s, 1H, CH), 7.17 (d, J = 8 Hz, 2H,
CH), 7.35 (s, 1H, CH), 7.42 (d, J = 8 Hz, 2H, CH), 10.48 (s, 1H,
CHO). 13C NMR (CDCl3) δ 21.6 (CH3), 84.2 (C C), 95.4 (C C), 102.4
(CH2), 106.0 (aromatic C), 111.9 (aromatic C), 119.3 (aromatic C),
123.9 (aromatic C), 129.3 (aromatic C), 131.5 (aromatic C), 132.0
(aromaticC), 139.3(aromaticC), 148.5(aromaticC), 152.4(aromatic
C), 190.1 (CHO). GC/TOF HRMS-EI: calcd for C17H12O3, 264.0786;
found 264.0796.
1-[4-(4-Fluorophenylethynyl)phenyl]ethanone
◦
1
Yellow crystals, m.p.: 105–107 C. H NMR (CDCl3) δ 2.63 (s, 3H,
CH3), 7.08 (t, J = 8 Hz, 2H, CH), 7.55 (dd, J = 8.4 Hz, J = 5.2 Hz,
2H, CH), 7.61 (d, J = 8.4 Hz, 2H, CH), 7.95 (d, J = 8 Hz, 2H,
CH). 13C NMR (CDCl3) δ 26.7 (CH3), 88.4 (C C), 88.5 (C C), 91.7
(C C), 115.8 (aromatic C), 116.1 (aromatic C), 118.9 (aromatic C),
118.9 (aromatic C), 128.1 (aromatic C), 128.4 (aromatic C), 131.8
(aromaticC), 133.8(aromaticC), 133.9(aromaticC), 136.4(aromatic
C), 161.7 (aromatic C), 164.2 (aromatic C), 197.4 (CO). API-ES: calcd
for C16H11FO, 238.0794; found 239.4 [M + H]+.
4-Naphthalen-1-ylethynyl-benzoic Acid Methyl Ester
◦
1
Brown crystals, m.p.: 109–113 C. H NMR (CDCl3) δ 3.93 (s, 3H,
CH3), 7.46 (t, J = 8 Hz, 1H, CH), 7.54 (t, J = 7.4 Hz, 1H, CH), 7.61
(t, J = 6.8 Hz, 1H, CH), 7.69 (d, J = 8.4 Hz, 2H, CH), 7.78 (dd,
J = 7.2 Hz, J = 4 Hz, 1H, CH), 7.86 (d, J = 8 Hz, 2H, CH), 8.06
(d, J = 8.4 Hz, 2H, CH), 8.41 (d, J = 8.4 Hz, 1H, CH). 13C NMR
(CDCl3) δ 52.4 (CH3), 90.7 (C C), 93.6 (C C), 120.4 (aromatic C),
c
Appl. Organometal. Chem. 2011, 25, 514–520
Copyright ꢀ 2011 John Wiley & Sons, Ltd.
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Y. Shi et al.
1-[4-(2,4,6-Trichloro-phenylethynyl)-phenyl]ethanone
T. Hashimoto, Y. Kondo, Y. Fujiwara, H. Seike, H. Takaya, Y. Tamada,
T. Ono, M. Nakamura, J. Am. Chem. Soc. 2010, 132, 10674; i)
M. A. J. Duncton, M. A. Estiarte, D. Tan, C. Kaub, D. J. R. O’Mahony,
R. J. Johnson, M. Cox, W. T. Edwards, M. Wan, J. Kincaid, M. G. Kelly,
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Mixture of the product and 2,4,6,2ꢁ,4ꢁ,6ꢁ-Hexachloro-biphenyl,
yellow crystal. 1H NMR (acetone-d6) δ 2.63 (s, 3H, CH3), 7.68 (s,
2H, CH), 7.76 (d, J = 8.4 Hz, 2H, CH), 8.07 (d, J = 8.4 Hz, 2H, CH).
GC/TOF HRMS-EI: calcd for C16H9Cl3O, 321.9719; found 321.9717.
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5-(4-Fluoro-phenylethynyl)-thiophene-2-carbaldehyde
Yellowcrystals;m.p.:98–99 ◦C.1HNMR(CDCl3)δ 7.08(t,J = 8.4 Hz,
2H, CH), 7.10 (d, J = 4 Hz, 1H, CH), 7.53 (t, J = 8 Hz, 2H, CH), 7.68
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(C C), 96.7 (C C), 115.8 (aromatic C), 116.1 (aromatic C), 132.5
(aromaticC), 132.7(aromaticC), 133.7(aromaticC), 133.8(aromatic
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X-ray Crystal Structure Determination of Pyrrole 5
The crystal suitable for the X-ray diffraction study was prepared by
slow crystallization of an ether solution of 5. Diffraction data for 5
were collected on a Siemens Smart CCD diffractometer equipped
with graphite monochromated Mo Kα radiation (λ = 0.71073 Å) at
293 K. The structure was solved by direct methods (SHELXS-97[21]
)
and subsequent difference Fourier syntheses, and refined by a full-
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Nonhydrogen atoms were refined with anisotropic displacement
parametersandhydrogenatomswereincludedintheridingmodel
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Acknowledgments
We are grateful to the Ministry of Science and Technology of China
and the Chinese National Natural Science Foundation (grant nos
20633020 and 20672017), the National Basic Research Program
of China (2009CB220009), the Program for Changjiang Scholars
and Innovative Research Team in University (IRT0711) and the K. &
A. Wallenberg Foundation for financial support of this work, and
the Swedish Energy Agency and the Swedish Research Council for
support.
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Supporting information
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Supporting information may be found in the online version of this
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