One-pot synthesis of substituted benzene via intermolecular [2+2+2] cycloaddition catalyzed by air-stable Ru(ii)-complex

Article abstract of DOI:10.1039/c0dt01502d

Intermolecular [2+2+2] cycloaddition reaction employing an air-stable ruthenium perchloro-cyclobutenonyl complex as a catalyst is reported. A series of internal alkynes were incorporated with dimethyl acetylene-dicarboxylate in a ratio of 1:2 to give vari

Full text of DOI:10.1039/c0dt01502d

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PAPER
One-pot synthesis of substituted benzene via intermolecular [2+2+2]
cycloaddition catalyzed by air-stable Ru(II)-complex†
Chung-Yeh Wu, Ying-Chih Lin,* Pi-Tai Chou, Yu Wang and Yi-Hung Liu
Received 1st November 2010, Accepted 2nd February 2011
DOI: 10.1039/c0dt01502d
Intermolecular [2+2+2] cycloaddition reaction employing an air-stable ruthenium
perchloro-cyclobutenonyl complex as a catalyst is reported. A series of internal alkynes were
incorporated with dimethyl acetylene-dicarboxylate in a ratio of 1 : 2 to give various substituted
benzenes in high yield and high chemoselectivity.
6
Introduction
to their versatile applications in material science and polymer
6i,7
chemistry. Their configurational effect have also been intensively
investigated. Moreover, these polycyclics are also employed as
precursors to synthesize triphenylenes that are widely utilized in
[2+2+2] cycloaddition reaction of alkynes, diynes and oligoynes
8
has become a vital and efficient atom-economical approach for
the construction of poly-substituted carbo- and heterocycles.
1
9
liquid crystal.
However, chemoselectivity remains a challenge for cross inter-
molecular [2+2+2] cycloaddition of two or three different alkynes,
especially the restriction for the use of substrates. Generally,
terminal aliphatic alkynes or internal alkynes with activated func-
tional groups are chosen for attaining better chemoselectivity.
Several diynes and triynes have also been applied in the [2+2+2]
It is also noteworthy that synthesis of the 1,2-diarylbenzene was
commonly carried out under inert atmosphere by using functional-
10
ized substrates, since air-tolerant [2+2+2] cycloaddition reaction
11
was rare. Therefore, searching for catalysts for cycloaddition
1a
12
to be used in air is of great interest. Herein, we report facile
one-pot, cross intermolecular [2+2+2] cycloaddition of 2 equiv.
of DMAD (2, dimethyl acetylene-dicarboxylate) with 1 equiv. of
2
1a
cycloaddition, generating extra rings on the final products. In
2c,3
2a,4
both half and complete intermolecular [2+2+2] cycloaddi-
tion reactions, diarylacetylene was considered as an inefficient
monoyne to react with the metallacycle intermediate I (see Scheme
various biaryl alkynes catalyzed by CpRu(PPh
3
)
2
(C
4
3
Cl O) (1) (see
Table 1) under mild conditions in air. The reaction gave desired
products with high yield and with high chemoselectivity.
1
(a)). Low yield and poor selectivity have been reported occasion-
4a,4b,5
ally even in the presence of excess diarylacetylene
Only few
Results and discussion
reports describe the [2+2+2] cycloaddition of multialkynes, linked
by aromatic-fragments to give polycyclic products.
The half sandwiched Ru(II) complex 1 bearing a cyclobutenonyl
was synthesized via
ization of ruthenium trichloroacetyl acetylide complex
Cp(PPh RuC CC( O)CCl (Scheme 1(b)). Complex 1 is
a solid state photo-induced isomer-
a
13
3
)
2
3
stable in common organic solvents under aerated as well as
moisturized conditions. To investigate the 2 : 1 cross trimerization
of 2 with various internal alkynes catalyzed by 1, 3-hexyne (3a) was
◦
first examined. The reaction was conducted in C
6
H
6
at 70 C in air
with a ratio of 2 : 3a = 1 : 1. The cross product 4a was isolated in 91%
yield with high chemoselectivity in 2 h. Cyclotrimerization of 2 to
yield hexamethyl mellitate 13 was known to be much faster than
the 2 : 1 cross trimerization. This decreased the yield of the desired
product, especially in the case of internal or diaryl alkynes as the
Scheme 1 (a) Complete intermolecular [2+2+2] cycloaddition; (b) com-
plex 1 prepared from photoisomerization.
4a,4b,5,14
third monoyne.
By changing the ratio of 2 : 3a to 1 : 2.5, the
Many polycyclics, such as phenyl-, naphthyl- or thienyl-
substituted benzenes, have attracted a great deal of attention due
homocyclo-trimerization of 2 was almost completely suppressed
resulting in a 92% yield of 4a. Aryl compound 4b was synthesized
under similar conditions from 3b in 89% yield. Excess alkyne was
readily recovered by flash column chromatography and recycled.
The reaction of 2 with diphenyl acetylene 3c, affording 4c, displays
effective suppression of 13, as the portion of 3c was increased at
Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan.
E-mail: yclin@ntu.edu.tw; Fax: +886-2-23636359; Tel: +886-2-33661657
†
Electronic supplementary information (ESI) available: Instrument infor-
mation and experimental procedure. CCDC reference numbers 728460–
28463. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c0dt01502d
7
◦
◦
70 C. Notably, at 25 C, 13 was obtained only in 2% yield. Use
3
748 | Dalton Trans., 2011, 40, 3748–3753
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a
Table 1 Cross [2+2+2] cycloaddition by complex 1
Table 2 lists results of the cycloaddition reaction of five diyne
substrates 3j–3n with 2. For 3j–3l, the consecutive cycloadditions
were carried out separately to give the aryl alkynes 4j–4l. This
reaction exhibits complete selectivity in the presence of excess
diynes to afford compounds 4 with four aromatic rings. After
running flash column to isolate the intermediates, then 5j–5l were
synthesized, respectively, by an additional step. 5j–5l appear as
white solids and could be purified by decanting the mixture
solution due to their poor solubility. For 3m and 3n possessing
cumulative triple bonds, the cycloaddition was achieved only for
the first triple bond, giving 4m and 4n, respectively. The steric
hindrance prohibits the second cycloaddition reaction.
The three-step cycloadditions of the triyne compound 3p with 2
were all carried out in the presence of excess 3p (Scheme 2(a)). All
three triple bonds in 3p were transformed to aryl fragments with
excellent selectivity. Trimerization of 2 was not observed during
the synthesis of 4p and 5p, possibly due to their multiple triple
bonds, which increases the probabilities of alkynes to approach the
metallacycle intermediate I. Ultimately, cycloaddition of 5p with 2
gave the pinwheel-like compound 6p in good yield and selectivity.
(See Scheme 2) Poor solubility of 6p in benzene also simplified the
purification process. The structure of 6p determined by an X-ray
c
Alkyne and
Entry Condition
Time
Ratio (2:3) (h)
Yield
(%)
b
Product
◦
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
3a, C
3a, C
3b, C
6
6
6
H
H
H
6
6
6
, 70 C 1 : 1
2
2
2.5
3
3
4a
4a
4b
4c
4c
4c
4c
4c
4c
4d
4e
4f
91(4)
92
89
◦
, 70 C 1 : 2.5
◦
, 70 C 1 : 2.5
◦
3c, C
3c, C
3c, C
3c, C
6
6
6
6
H
H
H
H
6
6
6
6
, 70 C 1 : 0.5
62(25)
81(12)
92(5)
96(2)
92(2.5)
83(2.5)
92
◦
, 70 C 1 : 2
◦
, 70 C 1 : 4
3
◦
, 25 C 1 : 4
144
22
5.5
3
3
4
◦
3c, THF, 70 C 1 : 4
3c, THF, reflux 1 : 4
◦
0
1
2
3
4
5
6
7
3d, C
3e, C
6
H
6
, 70 C 1 : 4
◦
6
H
6
, 70 C 1 : 4
91
◦
3f, C
3g, C
3g, C
3g, C
3h, C
6
H
6
, 70 C 1 : 6
88(2.5)
◦
d
6
6
6
6
H
H
H
H
6
, 70 C 1 : 7.5
4
4gs, 4ga (0.8 : 1) 88(6)
4gs, 4ga (0.5 : 1) 90(7)
4gs, 4ga (0.44 : 1) 87(8)
◦
diffraction analysis exhibits C -symmetry with the threefold axis
3
6
6
6
, 25 C 1 : 5
84
744
4
◦
, 8 C 1 : 1.3
passing through the central ring, A. The average dihedral angle
◦
◦
◦
, 70 C 1 : 7.5
4h
4i
71
90
between A and the ester-substituted ring, B, is ca. 60 ; and that
◦
3i, THF, 70 C 1 : 5
22
between B and the adjacent terminal ring, C, is ca. 70 . In the 3D
a
A mixture of 1 (0.006 mmol), 2 (0.116 mmol) and alkyne in the selected
solvent was stirred at the specified temperature. Excess alkynes could be
readily recovered unchanged by flash column and recycled. Isolated yields
based on 2 (yield of 13 in parentheses). Compounds 4gs and 4ga are syn-
framework of 6p, as shown in Scheme 2(b), a tetrahedral cavity is
formed by three C rings and one A ring.
b
c
d
and anti-form, respectively.
15
of THF instead of C
6
H , could also decrease the yield of 13. As
6
shown in Table 1, elevating the reaction temperature would speed
up the reaction. Furthermore, when the two dithienylacetylenes 3d
and 3e were employed, o-dithienylbenzenes 4d and 4e, respectively,
were obtained in >90% yield without giving 13. In the reaction of
dinaphthylacetylene, the steric hindrance was known to restrict the
access of alkyne to the metallacycle intermediate I (Scheme 1(a)),
2c,8a
resulting in much lower yield of o-dinaphthylbenzene.
Our
reaction of naphthylphenylacetylene 3f generated 4f in 88% yield.
For the bulkier dinaphthylacetylene 3g giving 4g, a higher ratio
of 3g was required to suppress the formation of 13. Alternatively,
lower temperature could be employed to effectively reduce the use
◦
of 3g. The catalytic activity of 1 remained effective at 8 C though
◦
the reaction took longer, while it ceased at ~0 C.
8f
Product 4g comprises syn and anti isomers, for which the
selectivity is found to be temperature dependent. The syn/anti
ratio varied from 0.44 : 1 to 0.80 : 1 as the temperature was
Scheme 2 (a) Synthesis of the pinwheel molecule 6p by a three-step trimer-
ization. Reaction conditions are shown in the parentheses (solvent/ratio
(2 : 3p, 4p or 5p)/reaction time/yield); (b) X-ray crystal structure of 6p (the
gray and black balls represent C and O atoms, respectively).
◦
◦
raised from 8 C to 70 C. Such an increase of syn-form at
higher temperature might be due to higher thermal energy,
thus overcoming the steric repulsion for the syn-conformation.
Separation of anti and syn isomers was readily accomplished by
sequential recrystallizations. Structures of both isomers have been
confirmed by single crystal X-ray diffraction analysis (See ESI†).
Also, alkynylphosphine oxide 3h was used to give 4h in 71% yield.
Reasonable formyl group tolerance was observed in the reaction
of di(4-formylphenyl)acetylene 3i, giving 4i in 90% yield.
Several functionalization reactions aiming at expanding the
scope of various polycyclics were also accomplished. As shown
in Scheme 3(a), photocyclizations of 4d and 5l were then carried
out in the presence of I to afford the aromatic compounds 7
2
and 8, respectively. The structure of 7 was also determined by
an X-ray diffraction study (see ESI†). Yellow solid compound 8
This journal is © The Royal Society of Chemistry 2011
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Table 2 Sequential cross [2+2+2] cycloaddition of diyne by complex 1
◦
at 70 C. Reaction conditions are shown in the parentheses (solvent/ratio
(
a
2 : 3 or 4)/reaction time/yield)
Diyne
4
5
Scheme 3 (a) Photocyclization reaction of 4d and 5l; (b) functionalization
reactions of 4c.
exhibits intense fluorescence (U
e.g. CH CN. Besides, the reaction of 4c with LiAlH
the tetrahydroxymethyl compound 9, and further bromination by
PBr afforded the tetra(bromomethyl)terphenyl 10. Treatment of
p
~ 0.35) maximized at 455 nm in
3
4
in THF gave
3
this tetrabenzyl bromide with 1-methylimidazole in THF under
reflux, afforded the imidazolium bromide 11 in high yield. Also,
hydrolysis of 4c in the presence of KOH gave the tetracarboxylic
acid 12 in good yield. These straightforward reactions pave the
way to a rather broad variety of new polycyclics.
Conclusion
In summary, the air-stable complex [Ru]-C
4
3
Cl O (1) efficiently
catalyzes the 2 : 1 intermolecular [2+2+2] cyclo-additions of
DMAD and various internal alkynes to give aromatic compounds
with dual substituents at the ortho position. This catalytic reaction
could be carried out in solvents of reagent grade and exhibits
high yield in air. Temperature control could decrease the amount
of excess alkyne required and achieve high chemoselectivity.
Cycloaddition reactions of multialkynes are also achieved by 1,
affording assorted polycyclic aromatic compounds. These facile,
one-pot reactions thus pave an avenue en route to synthesize a
broad spectrum of polycyclics via an atom-economical approach.
—
Experimental section
—
General procedures
The [2+2+2] cycloaddition reactions were performed in air.
All reagents were obtained from commercial suppliers. DMAD
(dimethyl acetylenedicarboxylate) was purified by dissolving in
C
6
H
6
, washed with NaHCO , H O, dried over Na SO , filtered,
3
2
2
4
evaporated and distilled under vacuum. The C and H analyses
were carried out with a Perkin–Elmer 2400 microanalyzer. Mass
spectra were recorded using a Thermo Finnigan LCQ Advantage
(
ESI) and Finnigan TSQ 700 spectrometers (EI). NMR spectra
were recorded on a Bruker AVANCE 400 instrument at 400 MHz
a
Isolated yields based on DMAD used.
1
31
13
(
H), 162.0 MHz ( P), or 100.6 MHz ( C) using SiMe
4
or 85%
3
750 | Dalton Trans., 2011, 40, 3748–3753
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1
3
1
H
3
PO
4
as a standard or an Avance 500 FT-NMR spectrometers.
OCH ), 3.14 (s, 6H, OCH ); C{ H} NMR (d, CDCl ): d = 166.9,
3
3
3
16
17
17
18
17
19
17
18
20
21
17
Alkynes 3b, 3d, 3e, 3f, 3g, 3h, 3i, 3j, 3k, 3l, 3m,
166.5, 142.5, 136.5, 133.8, 132.7, 130.9, 130.8, 128.6, 128.2, 127.6,
126.1, 125.5, 125.4, 124.0, 53.2, 52.2; EI-MS (20 eV) m/z: 562.16.
22
23
3n
and 3p were prepared according to the literatures.
Anal. Calcd for C34
4.67.
H
26
O : C, 72.59; H, 4.66. Found: C, 72.60; H,
8
General procedure for 2 : 1 cross intermolecular [2+2+2]
cycloaddition
1
4ga (anti-form). H NMR (d, CDCl
3
): d = 7.62–7.60 (m, 2H,
A typical procedure is described for 4c. To a mixture of 1 (5 mg,
Ph), 7.49–7.43 (m, 4H, Ph), 7.40–7.34 (m, 4H, Ph), 6.93–6.86 (m,
1
3
1
0
.006 mmol), DMAD (16.5 mg, 0.116 mmol), and diphenylacety-
4H, Ph), 3.90 (s, 6H, OCH
(d, CDCl ): d = 166.8, 166.4, 142.5, 136.3, 133.6, 132.6, 131.6,
130.7, 128.3, 127.8, 126.8, 126.0, 125.9, 125.6, 124.1, 53.2, 52.2;
3
), 3.15 (s, 6H, OCH
3
); C{ H} NMR
◦
lene (82.7 mg, 0.464 mmol) in C
6
H
6
(3 mL) was heated to 70 C for
3
3
h. Progress of the reaction was monitored by TLC, until complete
consumption of DMAD. After all DMAD was consumed, C
6
H
6
EI-MS (20 eV) m/z: 562.16. Anal. Calcd for C34
H
26
8
O : C, 72.59;
was removed by a rotary evaporator and the residue was passed
through silica gel flash column chromatography eluted with EA
and hexanes (1 : 5). Generally, the excess alkynes would be eluted
first, following by the cycloaddition products. The excess alkynes
could be recovered unchanged and recycled.
H, 4.66. Found: C, 72.60; H, 4.67.
1
4h. H NMR (d, CDCl ): d = 7.28–6.84 (m, 15H, Ph), 3.56 (s,
3
3H, OCH ), 3.44 (s, 3H, OCH ), 3.41 (s, 3H, OCH ), 3.08 (s, 3H,
3
3
3
1
3
1
OCH ); C{ H} NMR (d, C D ): d = 166.6, 166.6, 166.4, 165.1,
3
6
6
140.0, 139.9, 137.5, 137.5, 135.3, 134.6, 134.4, 134.4, 134.4, 133.0,
133.0, 132.9, 132.9, 132.5, 132.4, 132.2, 131.6, 131.6, 129.6, 129.1,
1
4
a. H NMR (d, CDCl
3
3
): d = 3.86 (s, 6H, OCH
), 1.17 (t, J = 7.5 Hz, 6H,
): d = 168.0, 166.7, 143.5, 135.0,
29.1, 53.0, 52.7, 23.6, 15.4; EI-MS (20 eV) m/z: 336.13. Anal.
Calcd for C18 : C, 59.01; H, 6.05. Found: C, 59.04; H, 6.11.
3
), 3.81 (s, 6H,
128.0, 53.3, 53.2, 52.8, 52.7; EI-MS (20 eV) m/z: 586.14. Anal.
OCH
CH
), 2.70 (q, J = 7.5 Hz, 4H; CH
2
1
3
1
Calcd for C32
H
27
9
O P: C, 65.53; H, 4.64. Found: C, 65.99; H, 4.82.
3
); C{ H} NMR (d, C
6
D
6
1
1
4
i. H NMR (d, CDCl
3
): d = 9.88 (s, 2H, CHO), 7.64 (d, J =
),
): d = 191.5, 166.5,
H
22
O
8
8
.0 Hz, 4H, Ph), 7.10 (d, J = 8.0 Hz, 4H, Ph), 3.88 (s, 6H, OCH
3.46 (s, 6H, OCH
65.8, 142.4, 140.9, 135.4, 135.3, 131.0, 130.0, 129.1, 53.3, 52.7;
3
1
3
1
1
3
); C{ H} NMR (d, CDCl
3
4
b. H NMR (d, CDCl ): d = 8.27 (d, J = 8.5 Hz, 2H, Ph),
.34 (d, J = 8.5 Hz, 2H, Ph), 3.90 (s, 3H, OCH ), 3.87 (s, 3H,
OCH ), 3.84 (s, 3H, OCH ), 3.48 (s, 3H, OCH ), 2.07 (s, 3H,
): d = 167.3, 166.5, 166.2, 166.0,
3
1
7
3
EI-MS (20 eV) m/z: 518.12. Anal. Calcd for C28
H, 4.28. Found: C, 65.34; H, 4.52.
22
H O10: C, 64.86;
3
3
3
1
3
1
CH
3
); C{ H} NMR (d, C
6
D
6
1
47.8, 146.6, 143.8, 140.9, 137.5, 135.3, 134.7, 133.1, 131.1, 130.1,
1
4
j. H NMR (d, CDCl
3
): d = 7.43 (m, 2H, Ph), 7.19 (m, 2H,
53.2, 53.2, 53.0, 52.6, 17.9; EI-MS (20 eV) m/z: 445.1. Anal. Calcd
Ph), 6.99–6.97 (m, 3H, Ph), 6.87–6.85 (m, 3H, Ph), 6.80–6.79 (m,
H, Ph), 6.71 (m, 2H, Ph), 3.53 (s, 3H, OCH ), 3.53 (s, 3H, OCH ),
3.20 (s, 3H, OCH ), 3.18 (s, 3H, OCH ); C{ H} NMR (d, C D ):
for C21
H
19
O10: C, 56.63; H, 4.30. Found: C, 56.27; H, 4.21.
2
3
3
1
3
1
1
3
3
6
6
4
c. H NMR (d, CDCl
3
): d = 7.12 (m, 6H, Ph), 6.94 (m, 4H,
1
3
1
d = 167.2, 167.2, 166.2, 166.2, 142.4, 141.8, 136.7, 136.4, 135.7,
Ph), 3.88 (s, 6H, OCH
3
), 3.45 (s, 6H, OCH
3
); C{ H} NMR (d,
135.4, 134.2, 131.6, 130.9, 130.3, 130.2, 129.4, 129.3, 128.3, 128.4,
C
6
D
6
): d = 167.3, 166.3, 142.5, 136.6, 135.5, 132.1, 132.0, 131.9,
127.8, 122.9, 122.6, 90.2, 88.9, 53.2, 53.2, 52.6, 52.5; EI-MS (20 eV)
130.0, 128.0, 127.8, 53.1, 52.4; EI-MS (20 eV) m/z: 462.13. Anal.
m/z: 562.16. Anal. Calcd for C34
H
26
O : C, 72.59; H, 4.66. Found:
8
Calcd for C26
H
22
O
8
: C, 67.53; H, 4.80. Found: C, 67.55; H, 4.82.
): d = 7.27 (m, 2H), 6.88 (m, 2H), 6.83
C, 72.68; H, 4.77.
1
4
d. H NMR (d, CDCl
3
1
1
3
1
5j. H NMR (d, CDCl ): d = 7.19–7.06 (m, 6H, Ph), 6.91 (d,
(
(
m, 2H), 3.86 (s, 6H, OCH
d, 25 C): d = 166.9, 165.9, 136.6, 130.6, 129.4, 128.2, 126.4,
3
), 3.57 (s, 6H, OCH
3
); C{ H} NMR
3
◦
J = 7.6 Hz, 2H, Ph), 6.80 (d, J = 7.6 Hz, 2H, Ph), 6.76 (d, J =
1
(
5.4 Hz, 4H, Ph), 3.85 (bs, 12H, OCH
s, 3H, OCH ), 3.40 (s, 3H, OCH ), 3.19 (s, 3H, OCH
): d = 167.1, 167.0, 166.7, 166.2, 166.2, 166.1, 166.1,
3
), 3.54 (s, 3H, OCH ), 3.43
3
3
1
24.8, 124.0, 53.3, 52.7; EI-MS (20 eV) m/z: 474.0. Anal. Calcd
1
1
for C22
H
18
O
8
S
2
: C, 55.69; H, 3.82. Found: C, 55.60; H, 3.88.
3
3
3
); C{ H}
NMR (d, C
6
D
6
1
4
e. H NMR (d, CDCl
3
): d = 7.10 (dd, J = 3.0, 5.0 Hz, 2H),
1
1
1
42.4, 142.4, 141.6, 141.4, 136.5, 136.3, 136.2, 136.1, 135.7, 135.6,
30.2, 130.2, 129.9, 129.7, 129.4, 129.2, 128.9, 127.9, 127.8, 127.6,
27.6, 53.4, 53.1, 52.6, 52.4, 52.4; EI-MS (20 eV) m/z: 846.22.
6
.98 (dd, J = 1.3, 3.0 Hz, 2H), 6.60 (dd, J = 1.3, 5.0 Hz, 2H), 3.85
13 1
(
s, 6H, OCH
3
), 3.54 (s, 6H, OCH
3
); C{ H} NMR (d, C
6
6
D ): d =
1
5
5
67.4, 166.1, 137.9, 136.4, 135.7, 129.9, 128.4, 125.1, 124.7, 53.1,
Anal. Calcd for C46
38
H O16: C, 65.25; H, 4.52. Found: C, 65.17; H,
2.6; EI-MS (20 eV) m/z: 474.0. Anal. Calcd for C22
H
18
O
8
2
S : C,
4.55.
5.69; H, 3.82. Found: C, 55.79; H, 3.90.
2
4
1
4
k . H NMR (d, CDCl
.01–7.11(12H, Ph), 3.90–3.45 (12H, OMe); C{ H} NMR (d,
): d = 191.4(CHO), 166.7–165.9 (CO Me), 141.5–128.0 (Ph),
3.4–52.5 (OMe); EI-MS (20 eV) m/z: 618.59. Anal. Calcd for
3
): d = 10.01–9.85 (2H, CHO),
1
4
f. H NMR (d, CDCl
3
): d = 7.66 (m, 2H, Ph), 7.36–7.25 (m,
13 1
8
C
5
4
3
H, Ph), 7.09 (m, 1H, Ph), 6.96–6.92 (m, 3H, Ph), 6.80 (m, 2H, Ph),
.90 (s, 3H, OCH ), 3.87 (s, 3H, OCH ), 3.45 (s, 3H, OCH ), 3.15
): d = 167.4, 166.8, 166.4,
66.3, 143.6, 141.3, 136.5, 136.2, 135.6, 134.0, 132.8, 131.7, 131.5,
30.6, 130.1, 129.1, 128.4, 128.2, 128.1, 127.9, 127.5, 127.3, 127.1,
26.0, 125.9, 125.8, 124.4, 53.2, 53.2, 52.5, 52.2; EI-MS (20 eV)
6
D
6
2
3
3
3
1
3
1
(
s, 3H, OCH
3
); C{ H} NMR (d, C
6
D
6
C
36
H
26
O10: C, 65.25; H, 4.52. Found: C, 65.17; H, 4.55.
1
1
1
24
1
5k . H NMR (d, C
6
6
D ): d = 9.70–9.49 (2H, CHO), 7.63–
6.32 (12H, Ph), 3.62–3.06 (12H, OMe); ESI MS for [M+Na] m/z:
m/z: 512.2. Anal. Calcd for C30
C, 70.52; H, 4.88.
H
24
O
8
: C, 70.31; H, 4.72. Found:
925.5. Anal. Calcd for C48
63.99; H, 4.33.
38
H O18: C, 63.86; H, 4.24. Found: C,
1
1
4
gs (syn-form). H NMR (d, CDCl
3
): d = 7.49–7.46 (m, 6H,
4l. H NMR (d, CDCl
3
): d = 7.31 (dd, J = 1.1, 5.1 Hz, 1H),
Ph), 7.17–7.13 (m, 4H, Ph), 7.09–7.03 (m, 4H, Ph), 3.90 (s, 6H,
7.27 (dd, J = 1.1, 5.1 Hz, 1H), 7.21 (dd, J = 1.1, 3.6 Hz, 1H), 7.03
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(
d, J = 3.7 Hz, 1H), 6.96 (dd, J = 3.6, 5.1 Hz, 1H), 6.91 (dd, J =
General procedure for photocyclization of 4d and 5l
To a mixture of 4d (100 mg, 0.21 mmol) (or 5l, 100 mg, 0.12 mmol)
3
1
3
1
1
8
.6, 5.1 Hz, 1H), 6.85 (dd, J = 1.1, 3.6 Hz, 1H), 6.71 (d, J = 3.7 Hz,
H), 3.85 (s, 3H, OCH ), 3.85 (s, 3H, OCH ), 3.62 (s, 3H, OCH ),
): d = 167.7, 166.7,
3
3
3
1
3
1
and I (10 mol%) in C (15 ml) was exposed to light from six 8 W
2
6
H
6
.56 (s, 3H, OCH
3
); C{ H} NMR (d, C
6
D
6
mercury lamps (365 nm) for 24 h (80 h for 5l) under air atmosphere.
Solvent was removed and the product was recrystallized from
65.7, 138.4, 136.7, 136.6, 136.5, 136.0, 135.5, 132.3, 131.4, 130.8,
29.5, 129.3, 128.7, 128.5, 127.9, 127.2, 126.6, 125.8, 122.4, 87.8,
5.5, 52.8, 52.7, 52.6; EI-MS (20 eV) m/z: 580.03. Anal. Calcd for
CH
2
Cl
2
and hexanes to yield a yellow solid as final product.
C
28
H
20
O
8
S
3
: C, 57.92; H, 3.47. Found: C, 57.99; H, 3.52
1
7
.
(73 mg, 73%): H NMR (d, CDCl
3
): d = 7.88–7.73 (m, 4H),
1
3
1
1
4.11 (s, 6H, OCH ), 3.90 (s, 6H, OCH ); C{ H} NMR (d, C D ):
5l. H NMR (d, CDCl
3
): d = 7.30 (d, J = 4.8 Hz, 2H), 6.91
3
3
6
6
d = 168.5, 166.5, 136.8, 132.3, 132.2, 129.3, 127.2, 125.3, 122.3,
53.6, 53.5; EI-MS (20 eV) m/z: 472.03. Anal. Calcd for C H O S :
(
dd, J = 3.7, 4.8 Hz, 2H), 6.75 (m, 2H), 6.58 (s, 2H), 3.85 (s, 12H,
13 1
OCH
3
), 3.65 (s, 6H, OCH
): d = 166.7, 166.5, 165.7, 138.9, 136.7, 136.5, 136.5,
36.0, 135.5, 130.7, 130.5, 129.4, 128.9, 128.0, 126.6, 53.2, 52.9,
2.7; EI-MS (20 eV) m/z: 864.09. Anal. Calcd for C40
5.55; H, 3.73. Found: C, 55.60; H, 3.78.
3
), 3.56 (s, 6H, OCH
3
); C{ H} NMR
22
16
8
2
C, 55.92; H, 3.41. Found: C, 55.99; H, 3.57.
(
d, CDCl
3
1
5
5
1
8.
(71 mg, 71%): H NMR (d, CDCl
3
): d = 8.04 (d, J = 5.5 Hz,
), 4.04 (s, 6H,
): d =
H
32
O
16
S : C,
3
2
H), 7.70 (d, J = 5.5 Hz, 2H), 4.18 (s, 6H, OCH
3
1
3
1
OCH
3
), 3.86 (s, 12H, OCH
3
); C{ H} NMR (d, CDCl
3
1
4m. H NMR (d, CDCl
3
): d = 7.42–7.35 (m, 5H, Ph), 7.22
), 3.89 (s, 3H,
168.6, 168.1, 166.4, 166.3, 135.6, 134.5, 133.9, 132.7, 131.6, 131.0,
128.9, 128.6, 127.7, 126.9, 124.7, 124.4, 54.3, 53.7, 53.4; EI-MS (20
eV) m/z: 860.05. Anal. Calcd for C H O S : C, 55.81; H, 3.28.
(
m, 3H, Ph), 7.08 (m, 2H, Ph), 3.97 (s, 3H, OCH
3
1
3
1
OCH
3
), 3.86 (s, 3H, OCH
): d = 166.6, 166.5, 165.9, 165.6, 145.3, 136.9, 136.6, 135.1,
31.6, 130.0, 129.8, 129.2, 129.1, 128.5, 128.2, 127.8, 124.8, 121.8,
00.6, 84.5, 53.1, 53.1, 52.9, 52.4; EI-MS (20 eV) m/z: 486.13.
: C, 69.13; H, 4.56. Found: C, 70.17; H,
3
), 3.50 (s, 3H, OCH
3
); C{ H} NMR (d,
4
0
28 16
3
CDCl
1
1
Anal. Calcd for C28
.66.
3
Found: C, 55.80; H, 3.29.
9. To a suspension of LiAlH (0.16 g, 4.2 mmol) in anhydrous
THF (10 mL), a solution of tetraester 4c (0.25 g, 0.54 mmol) in
4
H
22
O
8
◦
4
THF (10 ml) was added at 0 C under N
2
. The mixture was stirred
SO . After
removing THF on a rotary evaporator, the residue was extracted
with CH Cl . The extract was washed by brine and dried over
MgSO , and the solvent was removed to give the product as a
white solid. (0.15 g, 80%). H NMR (d, CD
for 8 h at RT, followed by hydrolysis using 2.0 N H
2
4
1
4
n. H NMR (d, acetone-d
Ph), 8.20 (m, 2H, Ph), 7.87 (m, 2H, Ph), 7.57 (m, 2H, Ph), 7.53–
.44 (m, 4H, Ph), 7.38 (m, 2H, Ph), 7.36 (m, 2H, Ph), 7.00 (m, 2H,
Ph), 4.05 (s, 3H, OCH ), 4.00 (s, 3H, OCH ), 3.88 (s, 3H, OCH ),
): d = 167.0, 166.0,
6
): d = 8.87 (s, 1H, Ph), 8.40 (s, 1H,
2
2
7
4
1
3
3
3
3
OD): d = 7.10–6.98
13 1
1
3
1
3
1
1
1
.02 (s, 3H, OCH
3
); C{ H} NMR (d, CDCl
3
(
(
6
m, 10H, Ph), 5.05 (s, 4H, CH
d, CD OD): d = 144.0, 141.3, 140.7, 138.9, 131.5, 128.2, 127.3,
0.5, 59.2; EI-MS (20 eV) m/z: 350.15 Anal. Calcd for C22
C, 75.41; H, 6.33. Found: C,75.01; H, 6.34.
2
), 4.50 (s, 4H, CH
2
); C{ H} NMR
66.0, 142.8, 137.2, 137.2, 132.8, 131.2, 130.5, 130.3, 130.3, 130.0,
29.0, 128.4, 128.3, 128.3, 127.3, 126.6, 126.6, 126.0, 125.9, 125.5,
15.2, 97.3, 94.8, 53.5, 53.4, 53.2; EI-MS (20 eV) m/z: 686.19.
3
H
22
4
O :
1
4
p. H NMR (d, CDCl
3
): d = 7.48–7.45 (m, 5H, Ph), 7,32–7.30
1
0. Phosphorus tribromide (80 ml, 0.86 mmol) was added
(
(
m, 6H, Ph), 7.19–7.17 (m, 3H, Ph), 7.06 (bs, 2H, Ph), 7.70–6.98
m, 2H, Ph), 3.88 (s, 6H, OCH ), 3.56 (s, 3H, OCH ), 3.46 (s, 3H,
): d = 166.9, 166.8, 166.0, 142.5,
dropwise to a solution of 9 (50 mg, 0.14 mmol) in anhydrous
THF (10 mL) at 0 C. After stirring for 2 h at RT, the mixture
was treated with water and then removed THF by on a rotary
evaporator. The residue was extracted with CH
was washed by brine and dried over MgSO , and the solvent was
removed. After chromatography on silica gel (CH Cl : hexanes =
: 10), 10 was afforded as yellow solid (77 mg, 90%). H NMR (d,
CDCl , 25 C): d = 7.16–7.05 (m, 10H; Ph), 4.95 (s, 4H; CH ), 4.37
bs, 4H; CH
3
3
◦
1
3
1
OCH
3
); C{ H} NMR (d, C
6
D
6
1
1
5
40.6, 137.2, 135.9, 135.6, 135.2, 133.6, 131.8, 131.5, 130.4, 130.2,
29.2, 128.5, 128.3, 127.9, 127.8, 123.2, 122.6, 90.3, 87.7, 53.1,
2.6, 52.4; EI-MS (20 eV) m/z: 662.19. Anal. Calcd for C42
2
2
Cl . The extract
4
H
30
8
O :
2
2
C, 76.12; H, 4.56. Found: C, 76.20; H, 4.59.
1
1
◦
1
5
p. H NMR (d, CDCl
3
): d = 7.37–7.21 (m, 8H, Ph), 7.09 (t,
3
2
1
3
1
(
1
2
); C{ H} NMR (d, CDCl
3
): d = 144.6, 137.6, 136.7,
J = 7.4 Hz, 2H, Ph), 6.95 (d, J = 7.3 Hz, 2H, Ph), 6.87 (d, J =
1
2
36.4, 129.5, 127.6, 127.2, 28.3, 25.5; EI-MS (20 eV) m/z: 597.81
Anal. Calcd for C22
2.96.
.5 Hz, 2H, Ph), 6.56 (t, J = 1.5 Hz, 2H, Ph), 6.37 (d, J = 2.7 Hz,
H, Ph), 3.85 (s, 12H, OCH ), 3.61 (s, 6H, OCH ), 3.42 (s, 6H,
); C{ H} NMR (d, CDCl ): d = 167.1, 166.6, 166.2, 142.3,
H
18Br : C, 43.89; H, 3.01. Found: C, 43.55; H,
4
3
3
1
3
1
OCH
3
3
1
1
5
40.3, 136.8, 136.1, 135.8, 135.5, 131.9, 131.6, 130.5, 130.3, 130.0,
25
11 . A mixture of 10 (40 mg, 0.066 mmol) and 1-
29.5, 129.2, 128.5, 128.3, 128.2, 127.8, 122.7, 122.7, 90.1, 87.8,
3.2, 53.1, 52.9, 52.4; EI-MS (20 eV) m/z: 946.25. Anal. Calcd for
methylimidazole (23 mL, 0.29 mmol) in anhydrous THF was stirred
and heated under reflux for 22 h. The precipitate was filtered,
washed by anhydrous THF (3 ¥ 10 mL), and dried under vacuum
to afford 11 as a white solid. (56 mg, 90%). H NMR (d, DMSO):
d = 9,.33 (s, 2H; NCHN), 9.27 (s, 2H; NCHN), 7.77, 7.73, 7.55
and 7.47 (s, 4 ¥ 2H, NCHCHN), 7.16 (m, 4H, Ph), 7.06 (m, 6H,
Ph), 5.80 (s, 4H, NCH
3.81 (s, 6H, CH
136.5, 136.5, 134.0, 133.3, 128.8, 127.7, 127.5, 127.1, 123.3, 123.1,
122.4, 47.9, 47.2, 35.9, 35.6.
C
54
H
42
O16: C, 68.49; H, 4.47. Found: C, 68.51; H, 4.59.
1
1
6
p. H NMR (d, CDCl
3
): d = 7.29 (3H, Ph), 7.20 (6H, Ph),
), 3.66 (s, 9H,
): d = 167.0,
6
.49 (s, 3H, Ph), 6.34 (6H, Ph), 3.83 (s, 18H, OCH
), 3.37 (s, 9H, OCH
66.2, 166.1, 166.1, 142.0, 139.6, 136.3, 136.2, 136.1, 135.9, 130.7,
3
1
3
1
OCH
3
3
); C{ H} NMR (d, C
6
D
6
1
1
1
6
2
1
), 5.30 (s, 4H, NCH
); C{ H} NMR (d, DMSO): d = 146.9, 137.3,
2
), 3.91 (s, 6H, CH ),
3
1
3
30.1, 130.1, 129.4, 128.2, 127.4, 53.2, 52.4; EI-MS (20 eV) m/z:
3
230.3. Anal. Calcd for C66
4.55; H, 4.45.
H
54
O24: C, 64.39; H, 4.42. Found: C,
3
752 | Dalton Trans., 2011, 40, 3748–3753
This journal is © The Royal Society of Chemistry 2011

View Article Online
1
2. To an aqueous solution of KOH(aq) (20 mg (0.36 mmol) in
M. Forster, B. Souharce, H. Thiem and U. Scherf, Angew. Chem., Int.
Ed., 2008, 47, 4070; (f) K. R. J. Thomas, T.-H. Huang, J.-T. Lin, S.-C.
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water (10 mL)), a solution of tetraester 4c (10 mg, 0.022 mmol)
in ethanol (20 mL) was added at RT. The mixture was stirred
and heated under reflux for 7 h. After evaporation of ethanol, the
acid was precipitated by addition of 2 N H
precipitation has been obtained. (pH ca. 6). The solid was filtered,
washed by water (3 ¥ 5 mL), and dried under vacuum to afford 12
as white solid. (7.5 mg, 85%). H NMR (d, DMSO): d = 7.15–7.14
m, 6H, Ph), 6.98–6.95 (m, 4H, CH
d = 167.4, 167.2, 140.8, 136.7, 135.0, 131.6, 129.4, 127.4.
1
1231; (g) Y. Zhou, W.-J. Liu, Y. Ma, H. Wang, L. Qi, Y. Cao, J. Wang
and J. Pei, J. Am. Chem. Soc., 2007, 129, 12386; (h) Q. Yan, Y. Zhou,
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2
SO until maximal
4
5
2
328; (i) J. D. Tovar, A. Rose and T. M. Swager, J. Am. Chem. Soc.,
002, 124, 7762.
7
8
(a) S. Xiao, H. Zhou and W. You, Macromolecules, 2008, 41, 5688;
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Shaheen, K. Kim and G. Rumbles, J. Am. Chem. Soc., 2007, 129,
1
1
3
1
(
2
); C{ H} NMR (d, DMSO):
1
8
4257; (c) J. P. Anzenbacher and M. A. Palacios, Nat. Chem., 2009, 1,
2.
(a) R. S. Walters, C. M. Kraml, N. Byrne, D. M. Ho, Q. Qin, F. J.
Coughlin, S. Bernhard and R. A. Pascal, J. Am. Chem. Soc., 2008,
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Single-crystal X-ray diffraction analysis of 4gs, 4ga, 6p and 7.
Single crystals of 4ga suitable for an X-ray diffraction study
were grown as mentioned above. A single crystal of dimensions
.20 ¥ 0.10 ¥ 0.15 mm was glued to a glass fiber and mounted
on a SMART CCD diffractometer. The diffraction data were
collected using 3 kW sealed-tube Mo KR radiation (T = 295
K). Exposure time was 5 s per frame. SADABS (Siemens area
detector absorption) absorption corrections were applied, and
decay was negligible. Data were processed, and the structure was
solved and refined by the SHELXTL program. Hydrogen atoms
were placed geometrically using the riding model with thermal
parameters set to 1.2 times that for the atoms to which the
hydrogen is attached and 1.5 times that for the methyl hydrogens.
3
0
(
d) R. A. Pascal and Q. Qin, Tetrahedron, 2008, 64, 8630; (e) C. Dell-
Erba, F. Gasparrini, S. Grilli, L. Lunazzi, A. Mazzanti, M. Novi, M.
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Grilli, L. Lunazzi, A. Mazzanti and M. Pinamonti, Tetrahedron, 2004,
26
6
0, 4451.
9
(a) D. Perez and E. Guitian, Chem. Soc. Rev., 2004, 33, 274; (b) M. D.
Watson, A. Fechtenkotter and K. Mullen, Chem. Rev., 2001, 101, 1267.
27
10 For Diels–Alder reaction, see: 7c and 8a; for Suzuki–Miyaura coupling,
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2
3
457; (b) X. Y. Yang, X. Don and K. Muellen, Chem.–Asian J., 2008,
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5
524.
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