Synthesis of m -terphenyl derivatives via domino Diels-Alder/Retro-Diels- Alder reaction of 1,3-dienic δ-sultones with alkynes

Article abstract of DOI:10.1055/s-0033-1340346

A highly regioselective synthetic method based on the domino Diels-Alder/retro-Diels-Alder reaction (DA/RDA) of 1,3-dienic δ-sultones with alkynes provides substituted m-terphenyls by elimination of SO₃. A variety of δ-sultones and alkynes were examined to determine the scope of the reaction. The de novo synthesized aromatic products were obtained using thermal, microwave, and high-pressure activation.

Full text of DOI:10.1055/s-0033-1340346

PAPER
▌531
pSaypenr thesis of m-Terphenyl Derivatives via Domino Diels–Alder/Retro-Diels–Alder
Reaction of 1,3-Dienic δ-Sultones with Alkynes
Synthesis of m-Terphenyl Derivatives
Jens Gaitzsch,a,b Victor Rogachev,*a,c Martin Zahel,a Peter Metza
a
Fachrichtung Chemie und Lebensmittelchemie, Organische Chemie I, Technische Universität Dresden, Bergstraße 66, 01069 Dresden,
Germany
Fax +49(351)46333162; E-mail: victor.rogachev@chemie.tu-dresden.de
b
Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
c
Department of Biotechnology and Organic Chemistry, Tomsk Polytechnic University, Leninstr. 30, 634050 Tomsk, Russian Federation
Received: 27.08.2013; Accepted after revision: 12.11.2013
Dedicated to Dr. Margit Gruner on the occasion of her 65th birthday
Ph
Abstract: A highly regioselective synthetic method based on the
Br
domino Diels–Alder/retro-Diels–Alder reaction (DA/RDA) of 1,3-
dienic δ-sultones with alkynes provides substituted m-terphenyls by
elimination of SO3. A variety of δ-sultones and alkynes were exam-
ined to determine the scope of the reaction. The de novo synthesized
aromatic products were obtained using thermal, microwave, and
high-pressure activation.
Ar
SO2
O
Ar
SO2
O
a
c
b
Ar
SO2
O
Ar
Ar
Ar
Ar
Key words: m-terphenyls, sultones, Diels–Alder reaction, alkynes,
high pressure
1a–g
2a–g
3a–g
4a–g
OMe
In the query to synthesize bioactive natural compounds
and functional materials, m-terphenyl derivatives are im-
portant intermediates.1 For this purpose it is essential to
develop novel reactions leading to these compounds. The
construction of the central benzene ring is a useful syn-
thetic approach for substituted m-terphenyls.
Ar =
Cl
Ph
OMe
Cl
a
b
g
c
d
e
f
Scheme 1 Synthesis and functionalization of 1,3-dienic δ-sultones,
including all residues processed. Reagents and conditions: a) SO3 (1
equiv); b) Br2 or NBS; c) 1a and Sonogashira conditions.
Here we present a new regioselective synthesis of substi-
tuted m-terphenyls based on the domino Diels–Alder/
retro-Diels–Alder (DA/RDA) reaction of 1,3-dienic δ-sul-
tones with alkynes. The domino DA/RDA reactions of α-
2H-pyranones2–4 or 1,2-diazines5–7 are known processes
for the de novo construction of benzene derivatives. How-
ever, the transformation of δ-sultones embedding a 1,3-di-
enic moiety was only reported once from our group. In our
example (Scheme 1),8 we only used a 1,3-dienic δ-sultone
with simple phenyl substituents, which has been inspired
by an earlier proposed reaction scheme.9 The potential of
this reaction is now shown using a wide range of sultones
and alkynes.
Sultones 2a–g were further functionalized with bromine
at the carbon neighboring the sulfur atom resulting in the
brominated sultones 3a–g. This functionality was then
used for a Sonogashira coupling11 with phenylacetylene
giving functionalized sultones 4a–g (Scheme 1). We now
have a large number of different 1,3-dienic δ-sultones in
hand to consider a further study of the DA/RDA sequence
(Scheme 2). When this strategy is applied to α-2H-pyra-
nones, often dimethyl acetylenedicarboxylate (DMAD, 5)
was used as a dienophile,12,13 resulting in derivatives of
benzene-1,2-dicarboxylic acid via carbon dioxide extru-
sion. Other dienophiles were now explored in order to get
more information about the regioselectivitiy of this cycli-
zation. Thus, ethyl propiolate (6) and phenylacetylene
(1a) were used as reasonable monosubstituted alkynes. To
see, whether a heteroanalogous reaction for cyano groups
is possible, the use of methyl cyanoformate (7) was also
examined.
Starting from the functionalized arylacetylenes 1a–g, δ-
sultones 2a–g were synthesized according to our method10
with dioxane sulfotrioxide or trimethylsilyl chlorosulfo-
nate as a sulfur trioxide source. The substituents at the
benzene rings ranged over a broad variety of different in-
ductive (I) and mesomeric (M) effects.
For all subsequent DA/RDA reactions it was decided to
use three methods of activation. In addition to the classical
thermal activation in a flask, the activation by microwave
radiation as well as high pressure were also examined.
SYNTHESIS 2014, 46, 0531–0536
Advanced online publication: 02.01.2014
DOI: 10.1055/s-0033-1340346; Art ID: SS-2013-Z0580-OP
© Georg Thieme Verlag Stuttgart · New York
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0
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1
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532
J. Gaitzsch et al.
PAPER
alkyne structure and testing the N-heteroanalogous 7 as a
dienophile, no reaction was observed.
Ar
R2
R1
SO2
+
O
R2
R1
Ar
O
Ph
DA/RDA
– SO3
+
2a
Ar
R2
R1
SO2
R
R2
Ar
Ph
8 R1 = CO2Et, R2 = H
9 R1 = Ph, R2 = H
10 R1 = H, R2 = Ph
9:10 = 91:9
6: R = CO2Et
1a: R = Ph
– SO3
Ar
R1
Ar
Scheme 2 Diels–Alder/retro-Diels–Alder reaction of 1,3-dienic
δ-sultones with alkynes. Ar = Ph, 4-MeC6H4, 4-ClC6H4, 3-ClC6H4,
4-PhC6H4, 4-MeOC6H4, 2-MeOC6H4; R1 = CO2Me, CO2Et, Ph;
R2 = CO2Me, H.
Scheme 3 Reaction of sultone 2a with phenylacetylene (1a) and eth-
yl propiolate (6)
Considering the reactivity, both monofunctionalized acet-
ylenes 6 and 1a have to be discussed separately. Ethyl
propiolate (6) showed a lower yield of cyclization product
than DMAD (5) using comparable microwave irradiation
(100 W). Interestingly, similar yields could be achieved
using thermal activation, but no products were observed
using high-pressure activation. Thus, the monocarboxyl-
ated alkyne 6 is in general less reactive than DMAD (5).
In contrast, the reactivity of phenylacetylene (1a) cannot
be judged as generally. Giving a lower yield under high-
pressure activation, microwave and thermal activation re-
sulted in unusually high yields of Diels–Alder products 9
and 10. In combination, yields of more than 100% related
to starting 2a could be determined. Here, SO3 leaving the
starting sultone 2a is recycled in situ, reacting with the ex-
cess of 1a to form new sultone 2a. Logically, these freshly
formed molecules can now enter the DA/RDA sequence
to form additional DA/RDA products 9 and 10.
The solvent-free method of microwave radiation has
proved to be a modern way of reducing reaction times as
well as increasing the yield in organic reactions,14,15 thus
amplifying reaction efficiency. Since high-pressure acti-
vation in liquid phase is a known method to realize Diels–
Alder reactions,16 it was also chosen for our approach.
With α-2H-pyranones the activation of the DA/RDA with
high pressure is not feasible due to the development of
gaseous CO2, slowing down or stopping the reaction. It is
therefore only applicable on a limited number of sub-
strates and may need reaction times over 300 hours.17 In
contrast, DA/RDA reactions of sultones lead to the elimi-
nation of SO3, which may immediately react with the ex-
cess of the alkyne. Consequently, no gaseous products can
be formed and high-pressure activation should be applica-
ble.
Monosubstituted alkynes 6 and 1a reacted with sultone 2a
to give one regioisomer predominantly. Interestingly,
both gave the sterically more hindered 1,2,4-substituted
terphenyls. While ethyl propiolate (6) gave only product
8, phenylacetylene (1a) gave both, 1,2,4-triphenylben-
zene (9) and 1,3,5-triphenylbenzene (10), in a 91:9 mix-
ture (Scheme 3, Table 1). The mixture of both isomers
could not be separated, but GC-MS revealed the ratio of
both isomers, while 13C NMR analysis showed, which iso-
mer was predominant.18 By replacing a carbon atom in the
Comparing the results, the order of reactivity discovered
by Kranjc and Kočevar3 for a DA/RDA reaction of pyra-
nones could be confirmed, if microwave radiation or ther-
mal activation is applied. Using high-pressure activation,
phenylacetylene (1a) shows a lower reactivity than
DMAD (5) and therefore switches places in the reactivity
scale (Figure 1).
Table 1 Reaction of Sultone 2a with Phenylacetylene (1a) and Ethyl Propiolate (6)
Alkyne
Conditions
Temp (°C)
Time (h)
Conversion of 2a (%)
Product, yield(%)
1a
1a
1a
1a
6
MW 100 W
MW 300 W
thermal
140
150
150
25
0.5
0.5
5
–
9 + 10 (74)
9 + 10 (130)a
9 + 10 (118)a
9 + 10 (30)
8 (21)
–
–
1300 MPa
MW 100 W
MW 300 W
thermal
50
0.5
0.5
8
–
120
150
150
25
34
100
100
0
6
8 (48)
6
8 (54)
6
1300 MPa
24
–
a Yield related to 2a, reaction with recycling of SO3.
Synthesis 2014, 46, 531–536
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Synthesis of m-Terphenyl Derivatives
533
CO2Me
CO2Et
CO2Me
N
Ph
sition to sulfur within the sultone leads to a complete loss
of DA/RDA reactivity. We suspect steric hindrance to
suppress the desired reactivity of the functionalized sul-
tones 3a and 4a.
>
>
>
(A)
CO2Me
As a logical subsequent step, now all remaining sultones
2b–g were treated with DMAD (5) to give terphenyls
11a–g, using all methods of activation (Scheme 4). The
results for thermal, microwave, and high-pressure activa-
tion are all comprised in Table 2.
1a
5
6
7
CO2Me
CO2Et
CO2Me
N
Ph
>
>
>
(B)
CO2Me
CO2Me
CO2Me
5
1a
6
7
SO2
O
R
R
DA/RDA
+
Figure 1 Reactivity scale of alkynes as dienophiles in the DA/RDA
with 1,3-dienic δ-sultones for microwave assisted activation (A) and
for high-pressure activation (B)
CO2Me
CO2Me
R
R
We suspect that any change in reactivity is due to the
Diels–Alder step of the reaction, since the subsequent ex-
trusion of SO3 yields a stable benzene structure and
should therefore not be rate-determining.
2a–g
5
11a–g
Scheme 4 Reaction of sultones 2a–g with dimethyl acetylenedicar-
boxylate (5)
Since reactions with DMAD (5) supplied the most stable
results and gave no further problems in the workup of the
crude product, it was chosen as the dienophile for further
studies with the sultones prepared.
The yields of the synthesized terphenyl derivatives 11a–g
via DA/RDA of sultones 2a–g with alkyne 5 reveal vari-
ous properties of the reaction. First of all, it is obvious that
there is only little dependency of the yield on the substit-
uents at the adjacent phenyl rings. All yields of terphenyls
11a–d are within a good range from 54–66%, for all acti-
vation methods. Here, the additional substituents of the
phenyl rings adjacent to the sultone ring have only little
influence on the DA/RDA reactivity of the central sultone
ring.
To determine the scope of the DA/RDA reactivity, a fur-
ther steric hindrance to the sultone was introduced, an α-
substitution of the sulfur atom. The further functionalized
sultones 3 and 4 were now applied as substrates in the ex-
plored DA/RDA reaction. As test substrates, the deriva-
tives of the basic sultone 2a, that is, 3-bromosultone 3a
and 3-phenylethynylsultone 4a,10 were chosen. Both sub-
stances were treated under similar conditions as for 2a.
Products with more than three phenyl ring chains can be
also synthesized by this method. Thus, the diphenylacety-
lene 2e gives the quinquiphenyl 11e using the DA/RDA
pathway. The structure of product 11e was confirmed via
X-ray crystal structure analysis (Figure 2).19
Unfortunately, in this case none of the methods of activa-
tion (thermal, microwave, high pressure) gave the desired
terphenyl. With 3-bromosultone 3a, the substrate was re-
isolated, while 3-phenylethynylsultone 4a decomposed
completely. These results show that a substitution in α po-
Table 2 Synthesis of m-Terphenyls 11a–g under Thermal, Microwave, and High-Pressure Activation
Sultone
R
Product
Activation, yield (%)
Thermal
MW
High pressure
2a
2b
2c
2d
2e
2f
H
11a
11b
11c
11d
11e
11f
55a,b
60c
58c
66c
22b
44c
34c
54a
57
61
65
24
54
34
67
57
63
66
54
11
24
4-Me
4-Cl
3-Cl
4-Ph
4-MeO
2-MeO
2g
11g
a Mixture of 1,1′:3′,1′′-terphenyl-4′,5′-dicarboxylic acid dimethyl ester 11a and 1,1′:3′,1′′-terphenyl-4′,5′-dicarboxylic acid anhydride 60:40
(mol/mol) for thermal activation and 74:26 (mol/mol) for microwave.
b Reaction temperature: 150 °C.
c Reaction temperature: 130 °C.
© Georg Thieme Verlag Stuttgart · New York
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534
J. Gaitzsch et al.
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m-Terphenyl Derivatives 11a–g from Sultones 2a–g; General
Procedure 1, Thermal Preparation
Sultone 2 (0.30 mmol) was placed into a 5 mL round-bottomed
flask, and dimethyl acetylenedicarboxylate (5, 390 mg, 2.75 mmol)
was added. The resulting suspension was stirred under an argon at-
mosphere for 7.5 h under the conditions mentioned in Table 2. The
resulting red-brown, highly viscous mixture solidified when it was
cooled to r.t. It was purified by flash chromatography with pentane–
EtOAc (5:1 for products 11a–e, 3:1 for products 11f, 11g) under
TLC control.
m-Terphenyl Derivatives 11a–g from Sultones 2a–g; General
Procedure 2, Microwave Preparation
Sultone 2 (0.30 mmol) was placed into a microwave test tube and
DMAD (5; 340 mg, 2.4 mmol) was added. The resulting suspension
was placed in a microwave apparatus and exposed to the radiation
(100 W, 20 min) with 5 min starting time and external cooling with
N2 gas. The resulting red-brown highly viscous crude product mix-
ture was purified by flash chromatography with pentane–EtOAc
(5:1 for products 11a–e, 3:1 for products 11f, 11g) under TLC con-
trol.
Figure 2 X-ray crystal structure of 11e
For high-pressure activation, the resulting yields of 11a–e
are considerably higher than the yields for both methoxy
substituted products 11f and 11g. Since both correspond-
ing starting sultones 2f and 2g are unstable,10 it is reason-
able that this lack of yield is due to their instability. For
microwave-assisted and thermal activation, the o-meth-
oxy derivative 2g gives the least amount of terphenylic
product. Here, steric hindrance due to the methoxy group
is the most probable reason for this behavior.
m-Terphenyl Derivatives 11a–g from Sultones 2a–g; General
Procedure 3, High Pressure Preparation
A solution of sultone 2 (0.30 mmol) in CH2Cl2 (10 mL) was trans-
ferred to a Teflon high-pressure test tube, and DMAD (5; 260 mg,
1.8 mmol) was added. The test tube was closed, inserted into the
high-pressure apparatus, and subjected to a pressure of 1300 MPa at
r.t. for 72 h. Then the high pressure was relieved, and the solvent
was removed at reduced pressure. Product 11 was isolated from the
resulting red-brown highly viscous mixture by flash chromatogra-
phy with pentane–EtOAc (5:1 for products 11a–e, 3:1 for products
11f, 11g) under TLC control.
In summary, we have shown that 1,3-dienic δ-sultones re-
act successfully with alkynes in the domino Diels–
Alder/retro-Diels–Alder (DA/RDA) reaction. The synthe-
sis of substituted m-terphenyls could be achieved with sul-
tones 2a–g and DMAD (5) or monosubstituted alkynes 1a
or 6 as dienophiles. As expected, an elimination of SO3
occurs, which immediately reacts with excess of the al-
General procedures 1–3 were also used for the experiments with
sultones 2a, 3a, 4a and dienophiles 1a, 6, and 7.
Ethyl 1,1′:3′,1′′-Terphenyl-4′-carboxylate (8)
kyne. The synthesis under microwawe or thermal activa- Yields: see Table 1; pale yellow oil; Rf = 0.44 (pentane–EtOAc,
5:1).
tion is carried out under solvent-free conditions. The
1H NMR: δ = 1.00 (t, J = 7.1 Hz, 3 H), 4.10 (q, J = 7.1 Hz, 2 H),
7.35–7.49 (m, 8 H), 7.58–7.67 (m, 4 H), 7.92 (d, J = 8.1 Hz, 1 H).
13C NMR: δ = 13.7 (CH3), 60.9 (CH2), 125.7 (CH), 127.2 (CH),
127.3 (CH), 128.0 (CH), 128.1 (CH), 128.4 (CH), 128.9 (CH),
129.5 (CH), 129.8 (C), 130.5 (CH), 139.9 (C), 141.6 (C), 143.1 (C),
144.0 (C), 168.5 (C=O).
activation using microwave radiation proved to be the
most efficient way to start the reaction, while high-
pressure activation is the cleanest way to perform this re-
action. The reaction with monosubstituted alkynes 1a or 6
gives 1,2,4-, but not 1,3,5-substituted central aromatic
rings with high regioselectivity. A substitution at the adja-
cent phenyl rings in sultones 2b–g shows only little influ-
ence on the reactivity of the sultones in the DA/RDA
sequence.
MS (ESI): m/z = 303 [M + H]+.
GC-MS: m/z (%) = 302 (60, [M]+), 257 (100, [M – C2H5O]+), 228
(40, [M – C3H6O2]+).
1,2,4-Triphenylbenzene (9)
Yields: see Table 1; brown oil; Rf = 0.44 (pentane–EtOAc, 5:1).
1H NMR: δ = 7.83–6.98 (m, 18 H).
13C NMR: δ = 126.11 (CH), 126.51 (CH), 126.58 (CH), 127.13 (2
CH), 127.42 (CH), 127.89 (2 CH), 127.92 (2 CH), 128.82 (2 CH),
129.41 (CH), 129.86 (2 CH), 129.90 (2 CH), 131.09 (CH), 139.54
(C), 140.35 (C), 140.58 (C), 140.98 (C), 141.11 (C), 141.78 (C).
Starting sultones 2a–g, 3a–g, and 4a–g were synthesized according
to our method.8 All commercially available compounds were used
as received, unless stated otherwise. Flash chromatography: Merck
silica gel 60 (40–63 μm). TLC: Merck silica gel 60 F254 plates with
UV detection of the spots. Solvent mixtures for chromatography are
reported as vol/vol ratios. Melting points: Kleinfeld Labortechnik
Electrothermal IA 9100 apparatus. 1H and 13C NMR: Bruker DRX-
500 (1H: 500 MHz, 13C: 126 MHz, CDCl3, δ, ppm, calibrated to the
residual resonance of the solvent, standard abbreviations). FT-IR
spectra: Nicolet 205 and Nicolet Avatar 360 spectrometer (cm–1,
standard abbreviations). Mass spectra: HP 1100 Bruker Esquire Ion
Trap (ESI/APCI, m/z, U = 10–50 V). Elemental analysis: Carlo
Erba Instruments EA 1108 and Hekatech EA 3000. Hofer high-
pressure apparatus (hydraulic press) up to 1400 MPa used for high-
pressure experiments. Microwave apparatus was a CEM Discover
System, model 908010.
MS (ESI): δ = 323 [M + NH4]+.
Dimethyl 1,1′:3′,1′′-Terphenyl-4′,5′-dicarboxylate (11a)
Yields: see Table 2; slowly crystallizing light yellow oil; mp 75–
77 °C; Rf = 0.26 (pentane–EtOAc, 5:1).
IR (ATR): 636 (m), 697 (s), 744 (s), 760 (s), 781 (m), 794 (m), 844
(w), 896 (m), 973 (m), 1000 (w), 1058 (m), 1070 (s), 1118 (s), 1199
(s), 1237 (s, br), 1266 (s, br), 1341 (m), 1372 (w), 1429 (m), 1463
(m), 1497 (w), 1598 (m), 1724 (s, br), 2849 (w), 2950 (w), 3033 (w),
3062 cm–1 (w).
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Synthesis of m-Terphenyl Derivatives
535
1H NMR: δ = 3.70 (s, 3 H), 3.84 (s, 3 H), 7.39–7.45 (m, 6 H), 7.46–
7.49 (m, 2 H), 7.64–7.66 (m, 2 H), 7.78 (d, J = 1.8 Hz, 1 H), 8.24
(d, J = 1.8 Hz, 1 H).
1H NMR: δ = 3.76 (s, 3 H), 3.98 (s, 3 H), 7.31–7.46 (m, 6 H), 7.53–
7.56 (m, 1 H), 7.64 (s, 1 H), 7.73 (d, J = 1.8 Hz, 1 H), 8.24 (d,
J = 1.8 Hz, 1 H).
13C NMR: δ = 52.23 (CH3), 52.65 (CH3), 127.18 (CH), 127.44
(CH), 127.95 (CH), 128.26 (CH), 128.31 (CH), 128.56 (CH),
128.73 (C), 128.97 (CH), 132.65 (CH), 133.32 (C), 139.01 (C),
139.22 (C), 141.14 (C), 142.17 (C), 166.15 (CO), 166.22 (C=O).
13C NMR: δ = 52.70 (CH3), 52.77 (CH3), 125.37 (CH), 126.80
(CH), 127.28 (CH), 127.85 (CH), 128.26 (CH), 128.43 (CH),
128.71 (CH), 129.07 (C), 129.62 (CH), 130.30 (CH), 132.30 (CH),
134.30 (C), 135.01 (C), 139.85 (C), 140.57 (C), 140.65 (C), 140.92
(C), 152.93 (C), 165.74 (C), 168.67 (C).
MS (ESI): m/z = 347 [M + H]+, 710 [2 M + NH4]+, 715 [2 M + Na]+.
MS (ESI): m/z = 432 [M + NH4]+.
Anal. Calcd for C22H18O4: C, 76.29; H, 5.24. Found: C, 76.19; H,
5.36.
Anal. Calcd for C22H16Cl2O4: C, 63.63; H, 3.88. Found: C, 63.95; H,
4.16.
Dimethyl 4,4′′-Dimethyl-1,1′:3′,1′′-terphenyl-4′,5′-dicarboxyl-
ate (11b)
Yields: see Table 2; yellow solid; mp 98–100 °C; Rf = 0.32
(pentane–EtOAc, 5:1).
Dimethyl 1,1′:4′,1′′:3′′,1′′′:4′′′,1′′′′-Quinquephenyl-4′′,5′′-di-
carboxylate (11e)
Yields: see Table 2; pale yellow solid; mp 169 °C; Rf = 0.19
(pentane–EtOAc, 5:1).
IR (ATR): 566 (m), 586 (w), 622 (w), 644 (w), 714 (w), 740 (m),
775 (s), 791 (s), 810 (s), 825 (m), 842 (w), 871 (w), 899 (w), 958
(m), 976 (w), 1068 (s), 1122 (s), 1191 (s), 1243 (s), 1278 (s), 1341
(m), 1434 (m) 1516 (w), 1562 (w), 1600 (w), 1636 (w), 1653 (w),
1685 (w), 1717 (s), 1771 (w), 1793 (w), 1829 (w), 1844 (w), 1870
(w), 1917 (w), 2116 (w), 2837 (w), 2916 (w), 2944 (w), 2992 (w),
3026 cm–1 (w).
1H NMR: δ = 2.32 (s, 3 H), 2.33 (s, 3 H), 3.64 (s, 3 H), 3.86 (s, 3 H),
7.13–7.25 (m, 6 H), 7.46 (d, J = 8.1 Hz, 2 H), 7.66 (d, J = 1.9 Hz, 1
H), 8.11 (d, J = 1.9 Hz, 1 H).
13C NMR: δ = 21.13 (CH3), 21.20 (CH3), 52.31 (CH3), 52.62 (CH3),
127.01 (2 CH), 127.04 (CH), 128.44 (2 CH), 128.72 (C), 129.06 (2
CH), 129.70 (2 CH), 132.49 (CH), 133.01 (C), 136.21 (C), 136.44
(C), 137.71 (C), 138.22 (C), 141.12 (C), 142.06 (C), 166.30 (C),
169.41 (C).
IR (ATR): 544 (m), 561 (s), 626 (m), 651 (m), 694 (s), 721 (s), 746
(s), 762 (s), 795 (m), 835 (s), 870 (m), 902 (m), 954 (m), 968 (m),
1002 (m), 1022 (m), 1069 (m), 1116 (s), 1197 (m), 1238 (s), 1274
(s), 1341 (m), 1432 (m), 1458 (m), 1486 (m), 1516 (w), 1601 (m),
1636 (w), 1652 (m), 1682 (m), 1698 (m), 1723 (s), 1771 (w), 2030
(w), 2056 (w), 2853 (w), 2922 (w), 2947 (w), 2998 (w), 3029 cm–1
(w).
1H NMR: δ = 3.75 (s, 3 H), 3.97 (s, 3 H), 7.38–7.41 (m, 2 H), 7.45–
7.54 (m, 7 H), 7.64–7.71 (m, 6 H), 7.74 (d, J = 4.1 Hz, 3 H), 7.87
(d, J = 1.9 Hz, 1 H), 8.29 (d, J = 1.9 Hz, 1 H).
13C NMR: δ = 52.48 (CH3), 52.74 (CH3), 127.08 (3 CH), 127.10 (3
CH), 127.39 (CH), 127.54 (CH), 127.60 (2 CH), 127.63 (CH),
127.75 (2 CH), 128.85 (2 CH), 128.88 (2 CH), 128.92 (C), 129.05
(2 CH), 132.53 (CH), 133.35 (C), 137.85 (C), 138.20 (C), 140.32
(C), 140.44 (C), 140.80 (C), 140.86 (C), 141.23 (C), 141.77 (C),
166.20 (C), 169.34 (C).
MS (ESI): m/z = 375 [M + H]+, 392 [M + NH4]+.
Anal. Calcd for C24H18O4: C, 76.99; H, 5.92. Found: C, 76.64; H,
5.65.
MS (ESI): m/z = 521 [M + Na]+.
Anal. Calcd for C34H26O4: C, 81.91; H, 5.26. Found: C, 81.72; H,
4.98.
Dimethyl 4,4′′-Dichloro-1,1′:3′,1′′-terphenyl-4′,5′-dicarboxyl-
ate (11c)
Yields: see Table 2; yellow oil; Rf = 0.30 (pentane–EtOAc, 5:1).
Dimethyl 4,4′′-Dimethoxy-1,1′:3′,1′′-terphenyl-4′,5′-dicarbox-
ylate (11f)
Yields: see Table 2; yellow oil; Rf = 0.29 (pentane–EtOAc, 3:1).
IR (ATR): 566 (m), 619 (w), 645 (w), 693 (w), 755 (s), 774 (m), 792
(s), 827 (s), 902 (w), 974 (m), 1013 (s), 1067 (s), 1091 (s), 1120 (s),
1177 (m), 1199 (s), 1243 (s), 1264 (s), 1342 (m), 1433 (m), 1456
(w), 1494 (m), 1558 (w), 1603 (w), 1635 (w), 1652 (w), 1685 (w),
1723 (s), 1771 (w), 1828 (w), 1844 (w), 1869 (w), 1917 (w), 2951
cm–1 (w).
1H NMR: δ = 3.64 (s, 3 H), 3.86 (s, 3 H), 7.39–7.25 (m, 6 H), 7.47–
7.50 (m, 2 H), 7.60 (d, J = 1.9 Hz, 1 H), 8.11 (d, J = 1.9 Hz, 1 H).
13C NMR: δ = 52.50 (CH3), 52.77 (CH3), 127.53 (CH), 128.42 (2
CH), 128.59 (2 CH), 129.00 (C), 129.22 (2 CH), 129.93 (2 CH),
132.21 (CH), 133.56 (C), 134.33 (C), 134.63 (C), 137.24 (C),
137.42 (C), 140.05 (C), 141.07 (C), 165.84 (C), 168.88 (C).
IR (ATR): 557 (m), 576 (w), 640 (w), 688 (w), 746 (m), 769 (m),
786 (m), 823 (s), 891 (w), 982 (m), 1024 (s), 1057 (m), 1071 (m),
1182 (m), 1176 (s), 1203 (m), 1239 (s), 1339 (w), 1391 (w), 1428
(m), 1458 (m), 1515 (m), 1541 (w), 1559 (w), 1577 (w), 1604 (m),
1652 (w), 1724 (s), 1773 (w), 1844 (w), 2055 (w), 2837 (w), 2951
(w), 3030 cm–1 (w).
1H NMR: δ = 3.72 (s, 3 H), 3.85 (s, 3 H), 3.86 (s, 3 H), 3.94 (s, 3 H),
7.93–7.02 (m, 4 H), 7.35 (d, J = 8.9 Hz, 2 H), 7.58 (d, J = 8.9 Hz, 2
H), 7.70 (d, J = 1.9 Hz, 1 H), 8.15 (d, J = 1.9 Hz, 1 H).
13C NMR: δ = 52.32 (CH3), 52.58 (CH3), 55.23 (CH3), 55.35 (CH3),
113.75 (2 CH), 114.40 (2 CH), 126.61 (CH), 128.27 (2 CH), 128.67
(C), 129.75 (2 CH), 131.51 (C), 131.71 (C), 132.18 (CH), 132.69
(C), 140.75 (C), 141.69 (C), 159.37 (C), 159.85 (C), 166.30 (C),
166.49 (C).
MS (ESI): m/z = 415 [M + H]+, 432 [M + NH4]+, 437 [M + Na]+.
Anal. Calcd for C22H16Cl2O4: C, 63.63; H, 3.88. Found: C, 63.45; H,
4.06.
MS (ESI): m/z = 407 [M + H]+, 424 [M + NH4]+.
Dimethyl 3,3′′-Dichloro-1,1′:3′,1′′-terphenyl-4′,5′-dicarboxyl-
ate (11d)
Anal. Calcd for C24H22O6: C, 70.92; H, 5.46. Found: C, 70.67; H,
5.52.
Yields: see Table 2; pale yellow oil; Rf = 0.29 (pentane–EtOAc,
5:1).
Dimethyl 2,2′′-Dimethoxy-1,1′:3′,1′′-terphenyl-4′,5′-dicarbox-
ylate (11g)
IR (ATR): 541 (w), 557 (w), 639 (w), 695 (s), 746 (m), 786 (s), 818
(w), 879 (m), 982 (w), 1067 (m), 1098 (m), 1123 (m), 1201 (m),
1242 (m), 1264 (m), 1339 (m), 1378 (w), 1433 (m), 1459 (m), 1476
(w), 1563 (w), 1594 (m), 1635 (w), 1651 (w), 1725 (s), 1772 (w),
1844 (m), 1917 (w), 2843 (w), 2951 (w), 3068 cm–1 (w).
Yields: see Table 2; yellow oil; Rf = 0.29 (pentane–EtOAc, 3:1).
IR (ATR): 570 (m), 632 (w), 751 (s), 794 (m), 826 (w), 851 (w), 874
(w), 903 (w), 934 (w), 973 (m), 1022 (s), 1044 (m), 1064 (m), 1107
(s), 1125 (s), 1174 (s), 1195 (s), 1244 (s), 1341 (m), 1395 (w), 1434
(m), 1459 (m), 1495 (m), 1578 (s), 1602 (w), 1635 (w), 1651 (w),
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2014, 46, 531–536

536
J. Gaitzsch et al.
PAPER
1685 (w), 1725 (s), 1771 (w), 1828 (w), 1844 (w), 1869 (w), 1918
(w), 2838 (w), 2950 (w), 2998 cm–1 (w).
1H NMR: δ = 3.56 (s, 3 H), 3.67 (s, 3 H), 3.73 (s, 3 H), 3.82 (s, 3 H),
6.85–6.99 (m, 4 H), 7.17–7.20 (m, 1 H), 7.24–7.31 (m, 3 H), 7.61
(d, J = 2.0 Hz, 1 H), 8.03 (d, J = 2.0 Hz, 1 H).
13C NMR: δ = 52.01 (CH3), 52.47 (CH3), 55.47 (CH3), 55.58 (CH3),
110.79 (CH), 111.30 (CH), 120.27 (CH), 120.90 (CH), 128.16 (C),
128.62 (C), 128.74 (C), 129.38 (CH), 129.43 (CH), 129.81 (CH),
130.77 (CH), 130.82 (CH), 133.13 (C), 135.97 (CH), 137.12 (C),
139.38 (C), 156.49 (C), 156.55 (C), 166.91 (C), 168.95 (C).
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MS (ESI): m/z = 407 [M + H]+, 424 [M + NH4]+.
Anal. Calcd for C24H22O6: C, 70.92; H, 5.46. Found: C, 70.63; H,
5.70.
Acknowledgment
Financial support of the Rosa-Luxemburg-Foundation is gratefully
acknowledged. We thank A. Jäger for the X-ray crystal structure
analysis of product 11e.
(19) Crystallographic data for the structure 11e have been
deposited with the Cambridge Crystallographic Data Centre
as supplementary publication number CCDC 869138. These
data can be obtained free of charge from the Cambridge
Crystallographic Data Centre via
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synthesis.SnuIomprifgtooatrinSugpIoi
n
nfomartit
References
www.ccdc.cam.ac.uk/data_request/cif or by writing to the
Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge CB2 1EZ, UK; fax: +44(1223)336033; E-mail:
deposit@ccdc.cam.ac.uk.
(1) Kays, D. L. Dalton Trans. 2011, 40, 769.
(2) Goel, A.; Ram, V. J. Tetrahedron 2009, 65, 7865.
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Synthesis 2014, 46, 531–536
© Georg Thieme Verlag Stuttgart · New York