Preparation of shape-persistent macrocycles with a single pyridine unit by double cross-coupling reactions of aryl bromides and alkynes

Article abstract of DOI:10.1021/jo2018944

A double Sonogashira-type coupling reaction between aryl bromides and alkynes using a catalytic Pd/XPhos (2-dicyclohexylphosphino-2′,4′, 6′-triisopropylbiphenyl) system was introduced as an efficient method for the synthesis of shape-persistent macrocycle

Full text of DOI:10.1021/jo2018944

Note
pubs.acs.org/joc
Preparation of Shape-Persistent Macrocycles with a Single Pyridine
Unit by Double Cross-Coupling Reactions of Aryl Bromides and
Alkynes
Ryu Yamasaki,* Atsushi Shigeto, and Shinichi Saito*
Department of Chemistry, Faculty of Science, Tokyo University of Science, Kagurazaka Shinjuku, Tokyo, Japan 162-8601
S
* Supporting Information
ABSTRACT: A double Sonogashira-type coupling reaction between aryl bromides and alkynes using a catalytic Pd/XPhos (2-
dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl) system was introduced as an efficient method for the synthesis of shape-
persistent macrocycles (SPMs). This approach is advantageous in the synthesis of SPMs with a single pyridine unit.
hape-persistent macrocycles (SPMs), composed of arylene
and ethynylene units, are versatile macromolecules and are
properties of SPMs when two or more pyridine moieties are
incorporated, so it is desirable to synthesize and analyze SPMs
incorporating a single pyridine unit. In this paper, we describe
the synthesis of SPMs with a single pyridine unit using a double
Sonogashira-type coupling reaction, using aryl bromide as the
substrate and under mild conditions. We found that by using a
highly active catalyst for the Sonogashira-type coupling
reaction,12,13 various dibromides could be used as the substrate
for cyclization via double Sonogashira-type coupling reactions.
The SPM precursors were prepared using conventional
Sonogashira coupling reactions, as shown in Scheme 1. The
Sonogashira coupling reaction between 2 (or 3) and 4 afforded
5 (or 6) in good yield. Compound 5 was further converted to
alkyne derivative 8 by an additional Sonogashira coupling
reaction with trimethylsilylacetylene and deprotection of the
trimethylsilyl group. The diiodide precursor was prepared as
shown in Scheme 2. Compound 3 reacted with an excess of 9
under Sonogashira coupling reaction conditions to afford
diiodide hemicycle 10. Compound 10 was reacted with
trimethylsilylacetylene and subsequent deprotection gave the
desired pyridine derivative 12.14
S
frequently used in host−guest chemistry.1,2 Twynsky et al. used
SPMs for the formation of supramolecules mediated by Pt−
bipyridine chelation outside the macrocycle cavity,3 and
Yoshida et al. reported an SPM−Sb complex which
incorporated an Sb atom inside the macrocycle.4 Crystallog-
raphy has shown that SPMs with large diameters can even
accommodate two Cu ions inside their cavities.5 SPMs are also
known to form aggregates in solution.6 Recently, the control of
SPM aggregation on surfaces has been intensively studied by
scanning tunneling microscopy.7
Efficient methods for SPM synthesis have been developed
since the 1990s by Moore et al.8 and Tobe et al.9 These
strategies can be classified into three main groups. The first
method involves an intermolecular coupling reaction, such as a
Sonogashira coupling reaction between an aryl iodide and an
alkyne, followed by an intramolecular coupling reaction under
dilute conditions.8 The second method uses a double-
cyclization reaction such as Glaser coupling of alkynes10 or a
Sonogashira coupling between an aryl iodide and an alkyne.11
Alkyne metathesis, which is very efficient, was recently
introduced as the third method.8d
Although many characteristics and functions of SPMs have
been studied, the diversity of SPM structures is not rich
enough. Many SPMs have an axis of symmetry, which will
facilitate synthesis and structural analysis, and most SPMs
which incorporate pyridine substructures contain two and more
pyridine moieties.1 It would be difficult to analyze the
With these substrates in hand, we screened the conditions for
the cross-coupling reaction (Table 1). In most cases, harsh
conditions are required for Sonogashira coupling using an aryl
bromide as the substrate.3c,15 Although various highly active
Received: September 16, 2011
Published: November 11, 2011
© 2011 American Chemical Society
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Note
Compound 1 was easily purified by silica gel chromatography
and was obtained in 24% yield (Table 1, entry 1). It is
noteworthy that neither the cyclized trimer nor tetramer was
isolated in this reaction.16 The higher temperature (60 °C)
allowed the reaction to finish in a shorter period of time,
without reducing the product yield (entry 2). The product yield
did not improve when the reaction was carried out at an even
higher temperature (80 °C) or when the catalyst loading was
increased or decreased (entries 3−5). With regard to substrate
concentration, the best result was observed when the
concentration, based on the total amount of solvent and 6
(or 8), was set at 10 mM; the product yield decreased when
half or twice the amount of solvent was used (entries 6 and 7).
The yield did not improve when the addition time was
extended to 20 h (entry 8). In contrast, the yield of 1 improved
marginally when the addition of 8 was completed in 5 h (entry
9). This result implies that catalyst decomposition occurred
when the reaction was continued for a longer period of time.
Further reduction of the injection time (3 h) resulted in a
slightly lower yield of the product (entry 10). The conditions
listed in entry 9 gave the best results for coupling reactions of
these substrates.
Scheme 1. Synthesis of Cyclization Precursors (1)
Two-component cyclizations by double Sonogashira-type
coupling reactions using aryl bromides as the substrates are
rare.17 The only example we could find in the literature was
reported by Lee et al., who used Sonogashira coupling reactions
with such substrates to obtain an SPM in 54% yield
[(PdCl2(PPh3)2, CuI, i-Pr2NH, 70 °C, 16 h].3c Although the
yields in our reactions were not very high, the yields are
comparable to those in other examples which used aryl iodides
as the substrates for the synthesis of similar SPMs.17
Scheme 2. Synthesis of Cyclization Precursors (2)
We used these optimized conditions in the coupling reaction
of aryl iodide (10) and diyne (8), but the product yield was low
(Scheme 3). This result tells us that more reactive substrates do
not necessarily give better yields of the product. The reversed
pair of diyne (12) and dibromide (5) were also subjected to
cyclization, and this combination gave a slightly lower yield of
1.
With these optimized conditions in hand, we used this
strategy to synthesize various SPMs and related compounds
(Figure 1). An N,N-dimethylaminopyridine (DMAP) moiety
was introduced into the SPM structure by cyclization of a
dibromide bearing a DMAP moiety with 8; 13 was isolated in
20% yield. An SPM with two pyridine moieties (14) was also
prepared, albeit in low yield. We assume that the low yield of
14 was partially a result of purification difficulties. Cyclization
using a starting material containing a flexible linker was also
examined under these conditions, and the macrocycle 15 was
obtained in 11% yield. This result implies that the preordered
molecular structures of 6 and 8 are beneficial in this double
coupling strategy. The larger SPM 16, linked with a butadiyne
unit, was obtained in 7% yield. The lower yield of 16 might be a
result of the instability of the butadiyne unit.
In summary, we have reported an efficient synthesis of SPMs
with a single pyridine unit by successive inter- and intra-
molecular Sonogashira-type coupling reactions between aryl
bromides and alkynes, catalyzed by Pd/XPhos. We optimized
the conditions for the coupling reaction with aryl bromide as
the substrate; this enabled synthesis of an SPM from 1,3-
diethynylpyridine (3) in short steps. The use of aryl bromides
in place of aryl iodides is rare, and usually requires harsh
condition. The use of aryl bromides, however, facilitates SPM
catalysts for Sonogashira-type coupling reactions were exam-
ined, we found that the Cu-free Sonogashira-type coupling
reactions with Pd/XPhos (2-dicyclohexylphosphino-2′,4′,6′-
triisopropylbiphenyl, see Table 1), originally reported by
Buchwald et al.,12 worked well for the coupling reaction of 6
and 8. This catalytic system is relatively stable and easy to
handle. To prevent intermolecular oligomerization, we carried
out the coupling reaction under pseudodilute conditions. Thus,
8 (0.054 mmol, 1 equiv) in 1,4-dioxane (0.54 mL) was added
to a mixture of 0.1 equiv of Pd(CH3CN)2Cl2, 0.3 equiv of
XPhos, CsCO3 (6 equiv), and 6 (0.054 mmol, 1 equiv) in 1,4-
dioxane (4.86 mL) via a syringe pump over 10 h at 60 °C.
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Note
Table 1. Coupling Reactions of 6 and 8
a
b
entry
Pd(CH3CN)2Cl2 (equiv)
XPhos (equiv)
conc (mM)
T (°C)
time (h)
yield (%)
1
2
0.1
0.1
0.1
0.2
0.05
0.1
0.1
0.1
0.1
0.1
0.3
0.3
0.3
0.6
0.15
0.3
0.3
0.3
0.3
0.3
10
10
10
10
10
20
5
40
60
80
60
60
60
60
60
60
60
40 (10)
14 (10)
15 (10)
15 (10)
72 (10)
15 (10)
48 (10)
26 (20)
6.5 (5)
5 (3)
24
24
21
19
0
3
4
5
6
10
0
7
8
10
10
10
7
9
28
24
10
a
b
Estimated concentration, which was defined as follows: (the amount of 6 used for the reaction)/(total amount of the solvent). Total reaction time,
including the addition time of 8. The addition time of 8 is indicated in parentheses.
NMR and 77.2 ppm for 13C NMR). Multiplicity is indicated by s
Scheme 3. Synthesis of 1 with Other Cyclization Precursors
(singlet), d (doublet), t (triplet), q (quartet) or m (multiplet).
Preparation of Dibromides 5 and 6. General Procedure. To
a mixture of CuI (46 mg, 0.24 mmol), Pd(PPh3)2Cl2 (84 mg, 0.12
mmol), and 4 (2.62 g, 6.6 mmol) were added Et3N (4.7 mL) and dry
THF (4.7 mL). The mixture was stirred for 10 min at room
temperature under Ar. After addition of diyne (2 or 3) (3.0 mmol),
the mixture was stirred for 1 h at room temperature. The solvent was
evaporated, filtered through a pad of Celite (washed with CH2Cl2),
diluted with CH2Cl2, and washed with brine. The organic layer was
dried over MgSO4 and evaporated. The crude product was purified by
silica gel column chromatography to give the desired product. 5 (66%,
1
pale yellow solid): mp 45−46 °C; H NMR (300 MHz, CDCl3) 7.66
(s, 1H), 7.56 (s, 2H), 7.47−7.45 (m, 4H), 7.40 (s, 2H), 7.32 (t, J = 7.5
Hz, 1H), 4.44 (s, 4H), 3.46 (t, J = 6.6 Hz, 4H), 1.66−1.57 (m, 4H)
1.39−1.29 (m, 12H), 0.89 (t, J = 6.9 Hz, 6H); 13C NMR (125 MHz,
CDCl3) 141.4, 134.9, 133.4, 131.8, 130.6, 129.2, 128.7, 125.0, 123.4,
122.4, 89.8, 88.7, 71.7, 71.1, 31.9, 29.9, 26.0, 22.8, 14.3; IR (KBr) 2930,
2856, 1598, 1561, 1479, 1442, 1354, 1213, 1182, 1114, 992, 892, 858,
828, 792, 732, 683, 533 cm−1. Anal. Calcd for C36H40Br2O2: C, 65.07;
H, 6.07. Found: C, 65.28; H, 6.15.
6 (77%, pale yellow solid): mp 58.0−58.2 °C; 1H NMR (300 MHz,
CDCl3) 7.65 (t, J = 4.5 Hz, 1H), 7.61−7.59 (m, 2H), 7.46−7.41 (m,
6H) 4.41 (s, 4H), 3,44 (t, J = 6.6 Hz, 4H), 1.61−1.54 (m, 4H) 1.36−
1.23 (m, 12H) 0.86 (t, J = 6.9 Hz, 6H); 13C NMR (75 MHz, CDCl3)
143.6, 141.5, 136.7, 133.7, 131.3, 129.6, 126.7, 124.0, 122.4, 89.3, 88.1,
71.6, 71.1, 31.8, 29.8, 26.0, 22.8, 14.2; IR (KBr) 2931, 2857, 2218,
1596, 1559, 1455, 1355, 1201, 1159, 1115, 907, 860, 807, 787, 731,
679, 551 cm−1. Anal. Calcd for C35H39Br2NO2: C, 63.17; H, 5.91; N,
2.10. Found: C, 63.10; H, 5.77; N, 2.04.
Preparation of Diyne 7. To a mixture of CuI (0.06 g, 0.314
mmol), Pd(PPh3)2Cl2 (0.112 g, 0.16 mmol), and dibromide 5 (3.48 g,
5.23 mmol) were added Et3N (8.7 mL) and dry THF (8.7 mL), and
the mixture was stirred for 10 min at 80 °C under Ar.
Trimethylsilylacetylene (2.2 mL, 15.7 mmol) was added, and the
mixture was stirred overnight. The solvent was evaporated, filtered
through a pad of Celite (washed with CH2Cl2), diluted with CH2Cl2,
and washed with brine. The organic layer was dried over MgSO4 and
evaporated. The crude product was purified by silica gel column
chromatography (hexane/CH2Cl2 5:1) to give 7 (3.18 g, 87%) as
synthesis. This method provides new and rapid access to SPMs
with single pyridine unit, and related compounds.
EXPERIMENTAL SECTION
■
General Information. Reagents were commercially available and
used without further purification unless otherwise noted. Compounds
2,18 3,19 4,20 and 920 were prepared as reported. Chemical shifts were
1
1
reported in delta units (δ) relative to chloroform (7.24 ppm for H
yellow oil. 7: H NMR (500 MHz, CDCl3) 7.65 (t, J = 1.5 Hz, 1H),
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Preparation of 10. To a mixture of 3 (0.172 g, 1.35 mmol) and
diiodide 9 (6 g, 13.5 mmol) were added Et3N (77.6 mL) and dry
toluene (77.6 mL), and then Ar was bubbled for 30 min at room
temperature. CuI (15 mg, 0.081 mmol) and Pd(PPh3)4 (94 mg, 0.081
mmol) were added, and the reaction mixture was stirred overnight.
The mixture was evaporated, filtered through a pad of Celite, diluted
with CH2Cl2, and washed with brine. The organic layer was dried over
MgSO4 and evaporated. The crude product was purified by silica gel
column chromatography (hexane/AcOEt 10:1) to give 10 (898 mg,
1
quant) as a pale yellow solid. 10: mp 59.2 °C; H NMR (300 MHz,
CDCl3) 7.83 (s, 2H), 7.70−7.64 (m, 3H), 7.51 (s, 2H), 7.45 (d, J = 4.8
Hz, 2H), 4.41 (s, 4H), 3.45 (t, J = 6.6 Hz, 4H), 1.65−1.51 (m, 4H),
1.40−1.28 (m, 12H), 0.88 (t, J = 6.6 Hz, 6H); 13C NMR (125 MHz,
CDCl3) 143.7, 141.4, 139.7, 137.2, 136.7, 130.4, 126.7, 124.1, 93.8,
89.3, 88.0, 71.6, 71.1, 31.8, 29.8, 26.0, 22.8, 14.2; IR (KBr) 2933, 2854,
2218, 1591, 1556, 1455, 1359, 1237, 1201, 1159, 1118, 983, 861, 804,
768, 728, 678, 552 cm−1. Anal. Calcd for C35H39I2NO2: C, 55.35; H,
5.18; N, 1.84. Found: C, 55.29; H, 4.95; N, 1.74.
Preparation of 12. To a mixture of CuI (10.5 mg, 0.055 mmol),
Pd(PPh3)2Cl2 (19.3 mg, 0.0275 mmol), and 10 (0.611 g, 0.918 mmol)
were added Et3N (1.5 mL) and dry THF (1.5 mL). The mixture was
stirred for 10 min at room temperature under Ar. Trimethylsilylace-
tylene (0.28 mL, 2.0 mmol) was added, and the reaction mixture was
stirred for 1 h. The mixture was evaporated, filtered through a pad of
Celite, and diluted with CH2Cl2. The organic layer was washed with
brine, dried over MgSO4, and evaporated. The crude product was
purified by silica gel column chromatography (hexane/AcOEt 20:1) to
give 11 (411 mg, 90%) as yellow oil. 11: 1H NMR (500 MHz, CDCl3)
7.64 (t, J = 7.5 Hz, 1H), 7.58 (s, 2H), 7.50 (s, 2H), 7.43−7.41 (m,
4H), 4.43 (s, 4H), 3.43 (t, J = 6.8 Hz, 4H), 1.62−1.57 (m, 4H), 1.38−
1.26 (m, 12H), 0.87 (t, J = 7.0 Hz, 6H), 0.23 (s, 18H); 13C NMR (125
MHz, CDCl3) 143.8, 139.7, 136.7, 134.6, 131.6, 131.1, 126.6, 123.8,
122.6, 104.1, 95.4, 88.9, 88.8, 72.0, 71.0, 31.9, 29.9, 26.0, 22.8, 14.2,
0.07; IR (KBr) 2931, 2857, 2219, 2157, 1590, 1557, 1454, 1359, 1249,
1159, 1108, 958, 844, 807, 759, 729, 685 cm−1. Anal. Calcd for
C45H57NO2Si2: C, 77.20; H, 8.21; N, 2.00. Found: C, 77.13; H, 8.22;
N, 1.92. To a solution of 11 (0.581 g, 0.83 mmol) in MeOH (2 mL)
and CH2Cl2 (0.5 mL) was added K2CO3 (0.286 g, 2.07 mmol) and the
reaction mixture was stirred overnight at the room temperature. The
mixture was evaporated. To the residue was added water, and the
mixture was extracted with CH2Cl2. The organic layer was washed
with brine, and dried over MgSO4 and evaporated under vacuo. The
crude product was purified by silica gel column chromatography
(hexane/AcOEt 10: 1) to afford 12 (0.300 g, 65%). 12 (65%, colorless
Figure 1. Prepared SPMs and related compounds.
1
solid): mp 35 °C; H NMR (500 MHz, CDCl3) 7.66 (t, J = 7.5 Hz,
7.55 (t, J = 1.5 Hz, 2H), 7.46−7.44 (m, 4H), 7.39 (d, J = 1.5 Hz, 2H),
7.30 (t, J = 7.5 Hz, 1H), 4.44 (s, 4H), 3.45 (t, J = 6.8 Hz, 4H), 1.46−
1.58 (m, 4H), 1.56−1.26 (m, 12H), 0.88 (t, J = 7.0 Hz, 6H), 0.22 (s,
18H); 13C NMR (125 MHz, CDCl3) 139.8, 135.1, 134.5, 131.9, 131.3,
131.0, 129.0, 124.0, 123.9, 123.7, 104.5, 95.5, 89.6, 89.4, 72.4, 71.3,
32.1, 30.1, 26.3, 23.1, 14.5, 0.4; IR (KBr) 2957, 2931, 2857, 2157,
1596, 1479, 1443, 1359, 1249, 1106, 958, 843, 792, 759, 732, 685, 532,
411 cm−1. Anal. Calcd for C46H58O2Si2 ; C, 79.03; H, 8.36. Found: C,
79.10; H, 8.08.
Preparation of Diyne 8. To a solution of 7 (2.96 g, 4.23 mmol)
in THF (84.6 mL) was added dropwise 12.7 mL of TBAF solution
(1.0 M in THF). After being stirred at room temperature for 3 h, the
mixture was diluted with water and extracted with CHCl3. The extract
was washed with brine and dried over MgSO4. After removal of the
solvent in vacuo, the residue was purified by silica gel column
chromatography (hexane/AcOEt 10:1) to provide 8 as a pale yellow
solid (1.64 g, 70%). 8: mp 48.2 °C; 1H NMR (300 MHz, CDCl3) 7.67
(s, 1H), 7.56 (s, 2H), 7.47−7.45 (m, 4H), 7.42 (s, 2H), 7.29 (t, J = 7.5
Hz, 1H), 4.45 (s, 4H), 3.46 (t, J = 6.6 Hz, 4H), 3.08 (s, 2H), 1.66−
1.57 (m, 4H), 1.41−1.28 (m, 12H), 0.88 (t, J = 6.6 Hz, 6H); 13C
NMR (125 MHz, CDCl3) 139.8, 134.8, 134.3, 131.7, 131.2, 131.1,
128.7, 123.6, 123.6, 122.8, 89.3, 89.2, 82.9, 78.0, 72.0, 71.1, 31.9, 29.9,
26.1, 22.8, 14.3; IR (KBr) 3283, 2936, 2854, 1594, 1476, 1361, 1151,
1120, 1025, 983, 889, 863, 782, 683, 627, 531 cm−1. Anal. Calcd for
C40H42O2: C, 86.60; H, 7.63. Found: C, 86.41; H, 7.64.
1H), 7.60 (s, 2H), 7.53 (s, 2H), 7.45−7.43 (m, 4H), 4.44 (s, 4H), 3.44
(t, J = 6.7 Hz, 4H), 3.07 (s, 2H), 1.63−1.57 (m, 4H), 1.38−1.26 (m,
12H), 0.87 (t, J = 6.9 Hz, 6H); 13C NMR (125 MHz, CDCl3) 143.8,
139.8, 136.7, 134.7, 131.8, 131.5, 126.7, 122.8, 122.7, 88.9, 88.8, 82.8,
78.1, 71.9, 71.1, 31.9, 29.9, 26.0, 22.8, 14.3; IR (KBr) 3293, 2931,
2861, 2221, 1781, 1589, 1558, 1450, 1357, 1241, 1157, 1110, 995, 871,
809, 732, 686, 655, 624, 547 cm−1. Anal. Calcd for C39H41NO2: C,
84.29; H, 7.44; N, 2.52. Found: C, 84.15; H, 7.38; N, 2.40.
Preparation of the Precursor (Dibromide) of 13 (Pre13-
DiBr). The dibromide of the cyclization precursor was prepared by
the coupling reaction of 2,5-diethynyl-4-dimethylaminnopyridine21
and 4 based on the method used for synthesis of 5. Pre13-DiBr (36%,
1
colorless solid): mp 112−114 °C; H NMR (300 MHz, CDCl3) 7.62
(s, 2H), 7.47 (s, 4H), 6.71 (s, 2H), 4.43 (s, 4H), 3.44 (t, J = 6.6 Hz,
4H), 3.05 (s, 6H), 1.62−1.55 (m, 4H), 1.38−1.28 (m, 12H), 0.87 (t, J
= 6.7 Hz, 6H); 13C NMR (125 MHz, CDCl3) 154.6, 143.4, 141.4,
133.8, 131.0, 129.7, 124.6, 122.4, 109.9, 90.5, 86.2, 71.8, 71.1, 39.5,
31.9, 29.9, 26.0, 22.8, 14.3; IR (KBr) 2930, 1590, 1524, 1427, 1384,
1216, 1169, 1099, 1025, 971, 856, 825, 808, 689 cm−1. Anal. Calcd for
C37H44Br2N2O2: C, 62.72; H, 6.26; N, 3.95. Found: C, 62.57; H, 6.06;
N, 3.78.
Preparation of the Precursor (Diyne) of 15 (Pre15-Diyne). A
mixture of resorcinol (0.207 g, 1.88 mmol), 4-pentyn-1-p-toluenesul-
fonate22 (0.95 g, 3.76 mmol), K2CO3 (1.43 g, 10.34 mmol), and LiBr
(0.245 g, 2.82 mmol) in dry DMF (3.62 mL) was stirred at 80 °C for
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Note
13 h. The mixture was cooled to room temperature, filtered, and
evaporated. The crude product was then purified by column
chromatography (hexane/CH2Cl2 5:1) to give Pre15-Diyne (335
mg, 66%) as a colorless solid. Pre15-Diyne: mp 54−56 °C; 1H NMR
(500 MHz, CDCl3) 7.14 (t, J = 8.3 Hz, 1H), 6.47−6.43 (m, 3H), 3.94
(t, J = 6.3 Hz, 4H), 2.25 (dt, J = 2.5 Hz, 7.0 Hz, 4H), 1.95 (t, J = 2.5
Hz, 2H), 1.91−1.85 (m, 4H), 1.73−1.67 (m, 4H); 13C NMR (125
MHz, CDCl3) 160.4, 130.1, 106.9, 101.6, 84.3, 68.8, 67.4, 28.5, 25.3,
18.3; IR (KBr) 2959, 2207, 2098, 1706, 1590, 1562, 1475, 1410, 1252,
1045, 847, 795, 761, 702, 682, 635, 507, 449 cm−1. Anal. Calcd for
C18H22O2: C, 79.96; H, 8.20. Found: C, 79.87; H, 8.41.
464 cm−1. Anal. Calcd for C50H58O2Si2: C, 80.38; H, 7.82. Found: C,
80.23; H, 7.76. To a solution of above compound (1 mmol) in MeOH
(2 mL) and CH2Cl2 (0.5 mL) was added K2CO3 (0.345 g, 2.5 mmol)
and the reaction mixture was stirred for 2 h at room temperature. The
mixture was evaporated and the residue was diluted with water, and
extracted with CH2Cl2. The organic layer was washed with brine, and
dried over MgSO4 and evaporated. The crude product was purified by
silica gel column chromatography to give the desired product. Pre16-
Diyne (55%, dark yellow oil): 1H NMR (400 MHz, CDCl3) 7.65 (t, J
= 1.2 Hz, 1H), 7.54 (s, 2H), 7.50 (dd, J = 1.4 Hz, 7.6 Hz, 2H), 7.47 (s,
2H), 7.45 (s, 2H), 7.31 (t, J = 7.8 Hz, 1H), 4.44 (s, 4H), 3.45 (t, J =
6.6 Hz, 4H), 3.07 (s, 2H), 1.64−1.53 (m, 4H), 1.39−1.24 (m, 12H),
0.88 (t, J = 6.8 Hz, 6H); 13C NMR (125 MHz, CDCl3) 140.0, 136.3,
135.0, 133.3, 132.0, 131.7, 128.9, 122.9, 122.5, 122.2, 82.6, 81.2, 80.7,
78.4, 74.9, 74.5, 71.8, 71.1, 31.9, 29.9, 26.0, 22.8, 14.2; IR (KBr) 3297,
Preparation of 1-[(Hexyloxyl)methyl]-3-iodo-5-[(2-
trimethylsilyl)ethynyl]benzene (17). BuLi (1.6 M) in hexane
(7.5 mL, 12 mmol) was added to a solution of 1-bromo-3-
[(hexyloxyl)methyl]-5-[(2-trimethylsilyl)ethynyl]benzene23 (2.2 g, 6
mmol) in anhydrous THF (16.5 mL) at −78 °C under nitrogen. After
1 h, a solution of 1,2-diiodoethane (3.4 g, 12 mmol) in THF (5 mL)
was added. The mixture was allowed to warm slowly to room
temperature (1 h), poured into Na2S2O3 aq, and extracted with
CH2Cl2. The organic layer was dried over MgSO4, and the residue
obtained after removal of solvents was subjected to column
chromatography (hexane/CH2Cl2 5:1) to provide 17 (1.69 g, 71%)
2930, 2857, 1587, 1444, 1362, 1247, 1107, 870, 793, 682, 463 cm−1
.
Anal. Calcd for C44H42O2: C, 87.67; H, 7.02. Found: C, 87.53; H, 7.16.
Preparation of the Precursor of 16 (Pre16-DiBr). Bis-2,6-[(4-
trimethylsilyl)-1,3-butadiyn-1-yl]pyridine was prepared by the same
method described for Pre16-Diyne using 1,3-diiodopydine was used
instead of 1,3-diiodobenzene. The product was isolated as brown solid
(78%): mp 170−172 °C; 1H NMR (300 MHz, CDCl3) 7.59 (t, J = 7.8
Hz, 1H), 7.40 (d, J = 7.8 Hz, 2H), 0.21 (s, 18H); 13C NMR (75 MHz,
CDCl3) 142.8, 136.7, 128.1, 93.1, 87.3, 74.74, 74.65 −0.3; IR (KBr)
2959, 2207, 2098, 1590, 1475, 1410, 1252, 1045, 847, 795, 761, 702,
682, 635, 507, 449 cm−1. Anal. Calcd for C19H21NSi2: C, 71.41; H,
6.62.; N, 4.38. Found: C, 71.26; H, 6.72; N, 4.17. To a solution of bis-
2,6-[(4-trimethylsilyl)-1,3-butadiyn-1-yl]pyridine (319 mg, 1 mmol) in
MeOH (0.83 mL) and THF (4.37 mL) was added K2CO3 (0.415 g, 3
mmol) and the mixture was stirred for 1 h at room temperature and
then Ar was bubbled through the mixture for 30 min. The mixture was
added to a suspension of CuI (19 mg, 0.10 mmol), Pd(PPh3)4 (58 mg,
0.05 mmol), 4 (0.873 g, 2.2 mmol), and i-Pr2NH (40 mL) in dry THF
(40 mL), and the reaction mixture was stirred overnight. The mixture
was evaporated the residue was filtered through a pad of Celite (eluent
CH2Cl2). The filterate was washed with brine, dried over MgSO4 and
evaporated. The crude product was purified by silica gel column
chromatography (hexane/AcOEt 20:3) to give Pre16-DiBr (599 mg,
84%) as glutinous brown oil. Pre16-DiBr: 1H NMR (500 MHz,
CDCl3) 7.62 (t, J = 8.5 Hz, 1H), 7.50 (s, 2H), 7.46−7.42 (m, 4H),
7.36 (s, 2H), 4.39 (s, 4H), 3.42 (t, J = 6.7 Hz, 4H), 1.60−1.55 (m,
4H), 1.35−1.21 (m, 12H), 0.85 (t, J = 7.0 Hz, 6H); 13C NMR (125
MHz, CDCl3) 142.7, 141.6, 136.7, 134.2, 131.8, 130.1, 128.0, 123.1,
122.4, 81.3, 80.2, 74.6, 74.2, 71.4, 71.1, 31.8, 29.8, 25.9, 22.7, 14.2; IR
(KBr) 2929, 2857, 2224, 1556, 1434, 1355, 1242, 1165, 1116, 859,
835, 806, 785, 728, 677,476 cm−1; HRMS-FAB (m/z) [M + H]+
Calcd. for C39H40Br2NO2 712.1420, found 712.1425.
General Procedure for the Macrocyclization. A two-necked
flask was evacuated and backfilled with argon (the cycle was performed
twice) and then charged under a positive pressure of argon with Pd
(CH3CN)2Cl2 (1.4 mg, 0.0054 mmol), XPhos (7.7 mg, 0.0162 mmol),
Cs2CO3 (106 mg, 0.324 mmol), 1.4-dioxane (4.86 mL, freeze-degassed
three times), and the aryl bromide (0.054 mmol). The slightly yellow
suspension was stirred for 5 min at 60 °C. Then the alkyne (0.054
mmol) in 1,4-dioxane (0.54 mL, freeze-degassed three times) was
added dropwise via syringe pump for 5 h. The flask was covered with
aluminum foil, and the reaction mixture was stirred for the indicated
period of time at the same temperature. The resulting brown
suspension was allowed to reach room temperature and evaporated.
To the residue was added water, and the mixture was extracted with
CH2Cl2. The combined organic layer was dried over MgSO4,
concentrated, and the residue was purified by silica gel chromatog-
raphy. The purity of the product was confirmed by GPC analysis using
CHCl3 as eluent.
1
as a yellow oil. 17: H NMR (500 MHz, CDCl3) 7.70 (d, J = 1.5 Hz,
1H), 7.61 (d, J = 1.5 Hz, 1H), 7.35 (s, 1H), 4.37 (s, 2H), 3.42 (t, J =
6.7 Hz, 2H), 1.60−1.56 (m, 2H), 1.34−1.26 (m, 6H), 0.87 (t, J = 7.0
Hz, 3H), 0.22 (s, 9H); 13C NMR (125 MHz, CDCl3) 141.1, 139.6,
136.6, 130.3, 125.2, 103.3, 96.0, 93.8, 71.6, 71.0, 31.9, 29.8, 26.0, 22.8,
14.3, 0.06; IR (KBr) 2954, 2931, 2861, 2159, 1589, 1558, 1457, 1434,
1357, 1249, 1157, 1103, 956, 848, 763, 686, 663 cm−1. Anal. Calcd for
C18H27IOSi: C, 52.17; H, 6.57. Found: C, 52.44; H, 6.63.
Preparation of the Precursor of 16 (Pre16-Diyne). To a
mixture of CuI (0.011 g, 0.06 mmol), Pd(PPh3)2Cl2 (0.021 g, 0.03
mmol), and 1,3-diiodobenzene (0.33 g, 1 mmol) was added Et3N (10
mL), and then the mixture was stirred for 10 min at 0 °C under Ar. 1-
Trimethylsilylbutadiyne24 (0.367 g, 3 mmol) was added, and the
reaction mixture was stirred 5.5 h. The mixture was evaporated, filtered
through a pad of Celite (washed with CH2Cl2), diluted with CH2Cl2,
and washed with brine. The organic layer was dried over MgSO4 and
evaporated. The crude product was purified by silica gel column
chromatography to give bis-1,3-[(4-trimethylsilyl)-1,3-butadiyn-1-yl]-
benzene (quant, yellow solid): mp 106−108 °C; 1H NMR (300 MHz,
CDCl3) 7.55 (t, J = 1.5 Hz, 1H), 7.43 (dd, J = 7.8 Hz, 1.6 Hz, 2H),
7.25 (t, J = 7.8 Hz, 1H), 0.22 (s, 18H); 13C NMR (75 MHz, CDCl3)
136.6, 133.5, 128.9, 122.2, 91.7, 87.7, 75.4, 75.2, −0.2; IR (KBr) 2959,
2207, 2098, 1706, 1590, 1562, 1475, 1410, 1252, 1045, 847, 795, 507,
449 cm−1. Anal. Calcd for C20H22Si2: C, 75.41; H, 6.96. Found: C,
75.23; H, 6.94. To a solution of bis-1,3-[(4-trimethylsilyl)-1,3-
butadiyn-1-yl]benzene (95 mg, 0.3 mmol) in MeOH (1.5 mL) was
added K2CO3 (0.207 g, 1.5 mmol) and the reaction mixture was
stirred for 1 h at room temperature. The mixture was diluted with HCl
aq and extracted with pentane. The organic layer was dried over
MgSO4 and slowly evaporated. The product (terminal alkyne) was
obtained as a colorless oil, which was used without further purification.
To a mixture of CuI (4.5 mg, 0.024 mmol), Pd(PPh3)4 (14 mg, 0.012
mmol), and 17 (0.274 g, 0.66 mmol) were added Et3N (0.47 mL) and
dry THF (0.47 mL). Then crude bis-1,3-[1,3-butadiyn-1-yl]benzene
was added and the reaction mixture was stirred for 1 h. The mixture
was evaporated, and filtered through a pad of Celite (eluent: CH2Cl2).
The filterate was washed with brine, dried over MgSO4, and
evaporated. The crude product was purified by silica gel column
chromatography (hexane/AcOEt 20:3) to give 1,3-bis[4-(3-henylox-
ylmethyl-5-(2-trimethylsilyl)ethynylbenzene)-1,3-butadiyn-1-yl]-
1
benzene (143 mg, 64%, glutinous brown oil): H NMR (300 MHz,
CDCl3) 7.65 (s, 1H), 7.52−7.48 (m, 4H), 7.43−7.41 (m, 4H), 7.30 (t,
J = 7.7 Hz, 1H), 4.42 (s, 4H), 3.43 (t, J = 6.6 Hz, 4H), 1.62−1.50 (m,
1 (16 mg (28% yield) from 0.054 mmol of the starting material,
4H), 1.37−1.27 (m, 12H), 0.87 (t, J = 7.0 Hz, 6H), 0.23 (s, 18H); 13
C
colorless solid): mp 164−165 °C; H NMR (300 MHz, CDCl3) 7.86
1
NMR (125 MHz, CDCl3) 139.8, 136.3, 134.9, 133.3, 131.8, 131.4,
128.9, 123.9, 122.5, 122.0; 103.9, 95.6, 81.3, 80.5, 74.9, 74.3, 71.9, 71.0,
31.9, 29.9, 26.0, 22.8, 14.3, 0.06; IR (KBr) 2956, 2159, 1725, 1587,
1444, 1407, 1363, 1249, 1156, 1110, 977, 927, 854, 792, 759, 682, 541,
(s, 1H), 7.79−7.77 (m, 2H), 7.68−7.65 (m, 3H), 7.52−7.45 (m, 12H),
7.33 (t, J = 9.6 Hz, 1H), 4.49 (s, 8H), 3.51−3.46 (m, 8H), 1.68−1.59
(m, 8H), 1.43−1.19 (m, 24H), 0.91−0.84 (m, 12H); 13C NMR (125
MHz, CDCl3) 143.9, 139.8, 139.7, 136.7, 135.8, 135.0, 134.6, 131.3,
10303
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The Journal of Organic Chemistry
Note
131.2, 130.9, 130.5, 130.5, 128.7, 126.5, 123.9, 123.7, 123.7, 123.6,
122.8, 89.54, 89.52, 89.4, 89.2, 89.1, 88.9, 72.2, 72.1, 71.1, 71.0, 31.9*,
29.9*, 26.1*, 22.9*, 14.3* (*signals of the hexyl groups were appeared
as a single set of peaks); IR (KBr) 2929, 2856, 2216, 1593, 1556, 1452,
1355, 1243, 1113, 983, 890, 863, 800, 728, 684, 537 cm−1; HRMS-ESI
(m/z) [M + H]+ calcd for C75H80NO4 1058.6082, found 1058.6066.
13 (12 mg, (20% yield) from 0.054 mmol of the starting material,
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: yamaryu@rs.kagu.tus.ac.jp; ssaito@rs.kagu.tus.ac.jp.
ACKNOWLEDGMENTS
■
This work is supported by Grants-in-Aid for Young Scientists
(B) (21750050) from the Ministry of Education, Culture,
Sports, Science and Technology (MEXT).
1
colorless solid): mp 242−243 °C; H NMR (500 MHz, CDCl3) 7.88
(s, 1H), 7.78 (s, 2H, br), 7.65 (s, 2H), 7.49−7.45 (m, 10H), 7.33 (t, J
= 4.5 Hz, 1H), 6.72 (s, 2H, br), 4.48 (s, 4H), 4.47 (s, 4H, br), 3.49−
3.45 (m, 8H), 3.05 (s, 6H, br), 1.64−1.60 (m, 8H), 1.60−1.28 (m,
24H), 0.88 (t, J = 4.2 Hz, 12H); 13C NMR (150 MHz, CDCl3) 143.5
(br), 139.7 (br), 139.6, 135.8, 134.9, 134.5, 131.2, 131.1 (br), 130.8,
130.5, 130.4, 128.6, 128.5, 123.7, 123.67, 123.65, 123.60, 123.0 (br),
109.7, 89.5, 89.4, 89.2, 72.1, 72.0, 71.0, 70.9, 39.6 (br), 31.9*, 29.9*,
26.0*, 22.8*, 14.3* (*signals of the hexyl groups were appeared as a
single set of peaks. Three carbons of internal alkynes were not
detected probably due to the overlap.); IR (KBr) 2931, 2861, 2221,
1589, 1527, 1450, 1427, 1357, 1272, 1118, 1018, 979, 887, 863, 825,
686, 539 cm−1; HRMS-ESI (m/z) [M + H]+ calcd for C77H85N2O4
1101. 6504, found 1101.6504.
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14 (10.6 mg (9% yield) from 0.108 mmol of starting material,
colorless solid): mp 205 °C; 1H NMR (500 MHz, CDCl3) 7.81 (t, J =
1.5 Hz, 4H), 7.67 (t, J = 7.6 Hz, 2H), 7.51 (s, 4H), 7.49 (s, 4H), 7.46
(d, J = 7.6 Hz, 4H), 4.49 (s, 8H), 3.48 (t, J = 6.7 Hz, 8H), 1.66−1.56
(m, 8H), 1.39−1.27 (m, 24H), 0.88 (t, J = 7.0 Hz, 12H); 13C NMR
(125 MHz, CDCl3) 143.9, 139.7, 136.7, 135.2, 131.2, 130.9, 126.4,
123.8, 122.8, 89.3, 89.1, 88.9, 72.1, 71.1, 31.9, 29.9, 26.1, 22.9, 14.3; IR
(KBr) 3424, 2923, 2854, 2383, 2306, 2221, 1720, 1589, 1558, 1457,
1357, 1241, 1157, 1103, 995, 871, 809, 732, 686, 539, 416 cm−1
;
HRMS-ESI (m/z) [M + H]+ calcd for C74H79N2O4 1059.6034, found
1059.6041.
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Feyter, S.; Tobe, Y. Chem. Commun. 2010, 8507.
15 (4.5 mg (11% yield) from 0.037 mmol of the starting material,
pale yellow solid): mp 65 °C; 1H NMR (300 MHz, CDCl3) 7.69−7.63
(m, 3H), 7.45−7.43 (m, 4H), 7.32 (s, 2H), 7.13 (t, J = 8.3 Hz, 1H),
6.58 (t, J = 2.8 Hz, 1H), 6.48 (dd, J = 2.8 Hz, 8.3 Hz, 2H), 4.44 (s,
4H), 4.04 (t, J = 6.0 Hz, 4H), 3.44 (t, J = 6.6 Hz, 4H), 2.48 (t, J = 6.6
Hz, 4H), 2.00−1.94 (m, 4H), 1.82−1.77 (m, 4H), 1.65−1.55 (m, 4H),
1.38−1.23 (m, 12H), 0.87 (t, J = 6.9 Hz, 6H); 13C NMR (75 MHz,
CDCl3) 160.6, 143.7, 139.5, 135.6, 130.8, 129.9, 126.4, 124.6, 122.4,
107.2, 100.5, 91.0, 80.6, 77.5, 77.4, 77.0, 72.1, 71.0, 70.9, 67.4, 31.9,
29.9, 28.4, 26.1, 25.5, 22.9, 19.2, 14.3; IR (KBr) 2927, 2856, 2218,
1717, 1590, 1557, 1492, 1455, 1285, 1183, 1155, 1104, 867, 806, 686,
453 cm−1; HRMS-ESI (m/z) [M + H]+ calcd for C53H60NO4
774.4517, found 774.4518.
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1
colorless solid): mp 125 °C; H NMR (300 MHz, CDCl3) 7.73 (s,
1H), 7.67−7.57 (m, 5H), 7.49−7.43 (m, 12H), 7.30 (t, J = 7.8 Hz,
1H), 4.46 (s, 8H), 3.46 (t, J = 6.6 Hz, 8H), 1.66−1.57 (m, 8H), 1.41−
1.20 (m, 24H), 0.88 (t, J = 6.9 Hz, 12H); 13C NMR (125 MHz,
CDCl3) 143.1, 140.0, 140.0, 136.8, 135.5, 132.8, 131.6, 131.3, 131.1,
128.9, 127.7, 123.8, 123.7, 122.6, 122.4, 121.9, 120.4, 89.5, 89.2, 82.0,
81.2, 80.6, 79.8, 75.0, 74.54, 74.47, 74.2, 72.0, 71.9, 71.15, 71.13, 31.9*,
29.9*, 26.1*, 22.9*, 14.3* (*signals of the hexyl groups were appeared
as a single set of peaks. Two carbons of internal alkynes were not
detected probably due to the overlap); IR (KBr) 2923, 2854, 2221,
Wettach, H.; Fritzsche, M.; Hoger, S.; Wan, L.-J.; Yang, H.-B.;
̈
Northrop, B. H.; Stang, P. J. J. Am. Chem. Soc. 2010, 132, 1328.
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1720, 1589, 1450, 1357, 1257, 1157, 1110, 871, 802, 732, 686 cm−1
;
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1154.6081, found 1154.6090.
ASSOCIATED CONTENT
■
S
* Supporting Information
Schemes for the synthesis of compounds which appeared in the
Experimental Section but were not mentioned in the main text;
NMR spectra. This material is available free of charge via the
Internet at http://pubs.acs.org.
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The Journal of Organic Chemistry
Note
oligomers. In addition, small amounts (ca. 15%) of the starting
materials (6 and 8) were recovered.
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