Synthesis of 1,4-diarylbuta-1,3-dienes through palladium-catalyzed decarboxylative coupling of unsaturated carboxylic acids

Article abstract of DOI:10.1002/adsc.201000897

It has been found that readily available hydroxylated cinnamic acids such as ferulic acid undergo palladium-catalyzed decarboxylative coupling with aryl iodides and internal alkynes in a 1:1:1 manner to produce 1,4-diarylbuta-1,3- dienes. The butadiene synthesis has also been achieved through the coupling of aryl halides with dienoic acids. Some of the products exhibit solid-state fluorescence.

Full text of DOI:10.1002/adsc.201000897

UPDATES
DOI: 10.1002/adsc.201000897
Synthesis of 1,4-Diarylbuta-1,3-dienes through Palladium-
Catalyzed Decarboxylative Coupling of Unsaturated
Carboxylic Acids
Mana Yamashita,a Koji Hirano,a Tetsuya Satoh,a,* and Masahiro Miuraa,*
a
Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
Fax : (+81)-6-6879-7362; phone: (+81)-6-6879-7361; e-mail: satoh@chem.eng.osaka-u.ac.jp or
miura@chem.eng.osaka-u.ac.jp
Received: November 29, 2010; Revised: December 27, 2010; Published online: March 4, 2011
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.201000897.
Abstract: It has been found that readily available
hydroxylated cinnamic acids such as ferulic acid un-
dergo palladium-catalyzed decarboxylative coupling
with aryl iodides and internal alkynes in a 1:1:1
manner to produce 1,4-diarylbuta-1,3-dienes. The
butadiene synthesis has also been achieved through
the coupling of aryl halides with dienoic acids.
Some of the products exhibit solid-state fluores-
cence.
Meanwhile, the decarboxylative coupling of arene-
and vinylcarboxylic acids with organic halides has at-
tracted much attention as a new, atom-economical
cross-coupling, because air- and water-stable, widely
available carboxylic acids can be employed as carbon
nucleophiles in place of organometallic reagents.[3,4]
Actually, a variety of alkenoic and dienoic acids such
as ferulic acid[5] and cinnamylidene acetic acid[6] are
widely present in biomass and readily available. They
appear to be promising building blocks for construct-
ing p-conjugated molecules. Recently, we have found
that hydroxylated cinnamic acids including ferulic
acid readily undergo decarboxylative arylation[7] and
vinylation[8] under relatively mild conditions com-
pared to those needed for the parent cinnamic acid.
Particularly, the vinylation using b-bromostyrenes as
À
Keywords: alkynes; C C coupling; decarboxyla-
tion; multicomponent reactions; palladium
Unsymmetrically substituted 1,4-diarylbuta-1,3-dienes coupling partners provides a simple method for 1,4-ar-
are of substantial importance for their application in ylbuta-1,3-diene synthesis (Scheme 1, via bond a for-
liquid crystals, illuminants, and non-linear optical ma- mation). In the context of our study on catalytic de-
terials.[1] Their syntheses have been conventionally carboxylative coupling,[9] we have found that the de-
conducted by Wittig-type or transition metal-cata- sired butadiene molecules can also be constructed
lyzed cross-coupling reactions.[2] These reactions usu- from more simple substrates, aryl iodides, internal al-
ally need activated substrates, prepared through com- kynes, and the cinnamic acids via two carbon-carbon
plicated multistep reactions, and are essentially ac- bond formations a, b shown in Scheme 1.[10] In addi-
companied by formation of stoichiometric amounts of tion, another approach to the target through the cou-
phosphorus- or metal-containing by-products.
pling of aryl halides with dienoic acids has also been
Scheme 1. Synthetic strategies for 1,4-diarylbuta-1,3-dienes.
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Mana Yamashita et al.
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Scheme 2. Reaction of iodobenzene (1a), diphenylacetylene (2a), and ferulic acid (3a).
investigated (via bond b formation). The results ob- N2, the corresponding three-component coupling
tained for these reactions are described herein. product 4a was obtained in 76% yield (Scheme 2).
First, the reaction of iodobenzene (1a), diphenyl- Minor amounts of stilbene 5 and naphthalene 6 were
acetylene (2a) (2 equiv.), and ferulic acid (3a) also detected by GC and GC-MS.
ACHTUNGTRENNUNG
(2 equiv.) was conducted under similar conditions to
Although treatment of 4-iodotoluene (1b) with 2a
those for the coupling of b-bromostyrenes with 3a. and 3a under similar conditions gave the three-com-
Thus, in the presence of PdACTHNUTRGNEUNG(OAc)2 (5 mol%), LiOAc ponent coupling product in 70% yield, its NMR spec-
(3 equiv.), and LiCl (1.5 equiv.) as catalyst, base, and tra indicated that it consists of (1E,3E)- and (1Z,3E)-
additive, respectively, in DMF at 1008C for 6 h under 4-(4-hydroxy-3-methoxyphenyl)-1-(4-methylphenyl)-
Table 1. Reaction of aryl iodides 1, diarylacetylenes 2, and cinnamic acids
3.[a]
[a]
Reaction
conditions:
[1]:[2]:[3]:[PdACHNUTGTREG(NUNN OAc)2]:ACHUTNRTGEGUN[NN LiOAc]:CAHTNUGTRNEN[UGN LiCl]=
0.4:0.8:0.8:0.02:1.2:0.6 (in mmol), DMF (2.5 mL) at 1008C for 6 h
under N2.
[b]
Isolated yield based on the amount of 1 used.
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Synthesis of 1,4-Diarylbuta-1,3-dienes through Palladium-Catalyzed Decarboxylative Coupling
and a diarylacetylene, in which the same aryl groups
are contained, with 3a gave the corresponding (3E)-
1,1,2,4-tetraarylbuta-1,3-dienes 4 as single major prod-
uct. Thus, as shown in Table 1, dienes 4b–f were ob-
tained from 1c–g and 2b–f (entries 1–5). Sinapinic
acid (3b) and coumaric acid (3c), which are also pres-
ent in plants as well as ferulic acid, underwent the
coupling with 1a and 2a to produce dienes 4g and 4h
(entries 6 and 7).
Some of 1,1,2,4-tetraarylbuta-1,3-dienes 4 obtained
above showed solid-state fluorescence in a range of
440–540 nm (see the Supporting Information). Nota-
bly, 4e exhibited a relatively strong emission com-
pared to a typical emitter, coumarin 153, by a factor
of 5.8 (lemis =478 nm, A versus B in Figure 1).
Interestingly, the reactions of sterically hindered
aryl iodides 1h–j with 4-octyne (2g) and 3a afforded
only (1E,3Z)-1,4-diaryl-3-propylhepta-1,3-dienes 4i–k
without any other isomers (Table 2). In these cases,
the yields of 4 significantly decreased at 1008C. In
contrast, the reaction of 1a, 2g and 3a gave a mixture
of (1E,3Z)- and (1E,3E)-isomers. At the present
stage, the origin of the difference remains obscure.
A plausible mechanism for the present three-com-
ponent coupling is illustrated in Scheme 3. Oxidative
Figure 1. Fluorescence spectra of 4e (A) and coumarin 153
(B) in the solid-state upon excitation at 422 nm.
1,2-diphenylbuta-1,3-dienes.[11] As expected, the reac- addition of aryl iodide 1 toward Pd(0) species gener-
tion using the substrate combination of an aryl iodide ated in situ followed by alkyne insertion and ligand
Table 2. Reaction of aryl iodides 1, 4-octyne (2g), and ferulic acid (3a).[a]
[a]
Reaction
conditions:
[1]:[2g]:[3a]:[PdACHTUNGTREG(NUNN OAc)2]:AHCTUNRTGENNG[UN LiOAc]:CAHTNUGTRNE[NUGN LiCl]=
0.4:0.8:0.8:0.02:1.2:0.6 (in mmol), DMF (2.5 mL) at 1408C for 4 h
under N2.
[b]
Isolated yield based on the amount of 1 used.
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Mana Yamashita et al.
UPDATES
Scheme 3. A plausible mechanism for the reaction of 1 with 2 and 3.
Scheme 4. Reaction of iodobenzene (1a), diphenylacetylene (2a), and 4-hydroxy-3-methoxystyrene (7).
exchange with cinnamic acid 3 gives a vinylpalladium also be produced through the coupling using bromo-
carboxylate intermediate A. The subsequent decar- benzene in place of 1a with 3d in the presence of
boxylation and reductive elimination afford butadiene PPh3 (10 mol%), in spite of a moderate yield (52%).
4.
Other iodides 1b, d–f also coupled with 3d smoothly
Another possible sequence may involve the initial to afford the corresponding substituted dienes 4m–p
decarboxylation of 3 to the corresponding styrenes (entries 2–5). In addition, sorbic acid (3e) underwent
which then couple with 1 and 2. During the three- the decarboxylative coupling with 1a to give 1-phenyl-
component coupling reactions, small amounts of such penta-1,3-diene (4q) as a mixture of geometric iso-
styrenes were actually detected by GC-MS.[7] Howev- mers (entry 6).
er, treatment of 4-hydroxy-3-methoxystyrene (7) with
1a and 2a gave 4a in a meaningfully lower yield
In summary, we have demonstrated that 1,4-diaryl-
AHCTUNGTREGbNNUN uta-1,3-dienes can be prepared through the palladi-
(44%, Scheme 4) than that from 1a, 2a, and 3a um-catalyzed decarboxylative coupling of w-arylalk-
(Scheme 2). The fact indicates that the latter sequence enoic and -dienoic acids with aryl halides in the pres-
AHCTUNGTRENNUNG
may partly participate, while the catalytic cycle in ence or absence of internal alkynes, respectively. Such
Scheme 3 may occur as the significant route. Which- unsaturated acids are apparently useful building
ever sequence is involved, the direct use of cinnamic blocks because of their wide and ready availability.
acids 3 rather than the corresponding styrenes seems
to be advantageous due to their availabilities.
As described above, the syntheses of 1,4-diarylbuta-
1,3-dienes could also be achieved by the decarboxyla-
tive coupling of 1 with dienoic acids. Thus, treatment
Experimental Section
of 1a with cinnamylidene acetic acid (3d) (2 equiv.) in
General Remarks
the presence of Pd(OAc)2 (5 mol%), AgOAc
AHCTUNGTRENNUNG
1H and 13C NMR spectra were recorded at 400 or 600 and
100 or 150 MHz, respectively, for CDCl3 solutions. MS data
were obtained by EI. GC analysis was carried out using a
silicon OV-17 column (i. d. 2.6 mmꢁ1.5 m) or a CBP-1 ca-
pillary column (i. d. 0.5 mmꢁ25 m). GC-MS analysis was
carried out using a CBP-1 capillary column (i. d. 0.25 mmꢁ
(2 equiv.), LiOAc (3 equiv.), and LiCl (1.5 equiv.) in
DMF at 1208C for 6 h gave (1E,3E)-1,4-diphenylbuta-
1,3-diene (4l) in 73% yield (entry 1 in Table 3). The
addition of AgOAc was essential to conduct the reac-
tion efficiently. Without it, the reaction was sluggish
to afford only a trace amount of 4l. Diene 4l could 25 m). The structures of all products were unambiguously
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Synthesis of 1,4-Diarylbuta-1,3-dienes through Palladium-Catalyzed Decarboxylative Coupling
Table 3. Reaction of aryl iodides 1 and dienoic acids 3.[a]
[a]
Reaction
conditions:
[1]:[3]:[PdACHTUNGRTNEN(GU OAc)2]:ACHUTGTNRENNUG[AgOAc]:ACHTUNEGRTG[NNUN LiOAc]:ACHTNUGTNER[NUGN LiCl]=
0.4:0.8:0.02:0.8:1.2:0.6 (in mmol), DMF (2.5 mL) at 1208C for 6 h
under N2.
[b]
[c]
[d]
Isolated yield based on the amount of 1 used.
At 1408C.
Determined by NMR.
determined by 1H and 13C NMR with the aid of NOE,
COSY, HMQC, and HMBC experiments.
Diarylacetylenes 2b–f were prepared according to pub-
lished procedures.[12] Other starting materials were commer-
cially available. Characterization data of all products are re-
ported in the Supporting Information.
The fluorescence analysis of some products was carried
out with the samples recrystallized from hexane.[13]
The following experimental procedures may be regarded
as typical in methodology and scale.
1H), 6.99 (d, J=8.5 Hz, 2H), 7.06–7.08 (m, 3H), 7.20 (d, J=
8.2 Hz, 2H), 7.25 (d, J=8.2 Hz, 2H), 7.37 (d, J=8.2 Hz,
2H); 13C NMR (150 MHz, CDCl3): d=31.1, 31.3, 31.4, 34.3,
34.4, 34.6, 55.6, 108.2, 114.3, 120.2, 123.8. 124.5, 124.6, 129.8,
130.7, 130.9, 131.0, 131.1, 131.3, 137.8, 138.5, 139.8, 140.1,
141.8, 145.0, 146.5, 148.6, 149.2, 149.9; HR-MS: m/z=
572.3651, calcd. for C41H48O2 (M+): 572.3654.
Acknowledgements
Decarboxylative Coupling of Aryl Iodides, Alkynes,
and Cinnamic Acids
This work was partly supported by Grants-in-Aid from the
Ministry of Education, Culture, Sports, Science and Technol-
ogy, Japan.
To
(0.4 mmol), internal alkyne 2 (0.8 mmol), cinnamic acid 3
(0.8 mmol), Pd(OAc)2 (0.02 mmol, 4 mg), LiOAc (1.2 mmol,
a 20-mL two-necked flask were added halide 1
ACHTUNGTRENNUNG
79 mg), LiCl (0.6 mmol, 25 mg), 1,2-diphenylethane (ca. References
40 mg) as internal standard, and DMF (2.5 mL). The result-
ing mixture was stirred under N2 at 100–1408C for 4–6 h.
GC and GC-MS analyses of the mixture confirmed forma-
tion of 4. After cooling, the reaction mixture was poured
into dilute aqueous HCl (50 mL), extracted with ethyl ace-
tate (50 mL, three times), washed with saturated aqueous
NaCl (50 mL), and dried over Na2SO4. The product was iso-
lated by column chromatography on silica gel using hexane-
ethyl acetate as eluant.
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