Synthesis and bifunctional asymmetric organocatalysis of helical poly(phenylacetylene)s bearing cinchona alkaloid pendants via a sulfonamide linkage

Article abstract of DOI:10.1002/pola.26678

Four novel helical poly(phenylacetylene)s with amino-functionalized cinchona alkaloid pendant groups connecting to the phenyl rings through a sulfonamide linkage were synthesized by the polymerization of the corresponding phenylacetylene monomers using Rh

Full text of DOI:10.1002/pola.26678

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Synthesis and Bifunctional Asymmetric Organocatalysis of Helical
Poly(phenylacetylene)s Bearing Cinchona Alkaloid Pendants via a
Sulfonamide Linkage
Hiroki Iida, Zhenglin Tang, Eiji Yashima
Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Nagoya 464–8603, Japan
Correspondence to: E. Yashima (E-mail: yashima@apchem.nagoya-u.ac.jp)
Received 30 November 2012; accepted 8 March 2013; published online 19 April 2013
DOI: 10.1002/pola.26678
ABSTRACT: Four novel helical poly(phenylacetylene)s with
amino-functionalized cinchona alkaloid pendant groups con-
necting to the phenyl rings through a sulfonamide linkage
were synthesized by the polymerization of the corresponding
phenylacetylene monomers using Rh1(2,5-norbornadiene)[(g6-
C6H5)B2(C6H5)3] (Rh(nbd)BPh4) as the catalyst. The optically
active sulfonamide-linked polymers adopted a helical confor-
mation with an excess of one-handedness as supported by the
appearance of the induced Cotton effects in the main-chain
chromophore regions, and efficiently catalyzed the enantiose-
lective methanolytic desymmetrization of a cyclic anhydride
and aza-Michael addition of aniline to chalcone, thereby pro-
ducing the corresponding optically active products up to 86%
enantiomeric excess. However, their enantioselectivities from
the methanolytic desymmetrization were slightly lower than
those catalyzed by the corresponding cinchona alkaloid-bound
monomers. On the other hand, during the asymmetric aza-Mi-
chael addition, a unique enhancement of the enantioselectivity
was observed for several sulfonamide-linked helical polymers,
and thus affording a remarkably higher enantioselectivity com-
pared to those of the corresponding monomers and nonhelical
polymers bearing the identical cinchona alkaloid residues.
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KEYWORDS: catalysts; chiral; cinchona alkaloid; helical structure;
polyacetylenes
the optically active cinchona alkaloid pendants.5 We found
that these optically active helical polymers could be utilized
as an efficient polymeric organocatalyst for the asymmetric
conjugated addition and enantioselective Henry reaction5(a,b)
as well as chiral stationary phases for separating enan-
tiomers during high-performance liquid chromatography
(HPLC).5(c) In particular, the amide-linked quinine-containing
polymer (poly-AQn) successfully catalyzed the asymmetric
Henry reaction of benzaldehydes with nitromethane, yielding
the corresponding optically active products up to 94% enan-
tiomeric excess (ee), whose enantioselectivity was remark-
ably higher than those catalyzed by the corresponding
nonhelical poly-AQn (18% ee) and the monomer (28%
ee).5(b) These results clearly indicated a type of synergistic
effect of the induced helical chirality that enhanced the enan-
tioselectivity. Although a number of optically active helical
polymer-based asymmetric catalysts have been developed,
successful examples showing high (more than 80% ee) and
better enantioselectivities than those of the corresponding
monomers have been limited,6 except for the helical poly(-
phenylacetylene)-based organocatalysts developed by our
INTRODUCTION Naturally occurring cinchona alkaloids con-
sisting of two pseudoenantiomeric pairs, such as cinchoni-
dine (Cd)/cinchonine (Cn) and quinine (Qn)/quinidine (Qd),
have been extensively used as versatile asymmetric organo-
catalysts for a wide variety of asymmetric transformation
reactions.1,2 It has been recently shown that cinchona alka-
loid-based bifunctional organocatalysts carrying hydrogen-
bond-donating functionalities are highly effective for the
diverse asymmetric transformation reactions in which the
hydrogen-bond donors cooperatively stabilize the transition
state.1(d,e),3 Sulfonamides possessing an acidic hydrogen are
recognized as one of the most useful scaffolds for the hydro-
gen-bond-donor catalysts, and thus several efficient bifunc-
tional organocatalysts combining cinchona alkaloids and
sulfonamide residues have been developed.4
We previously prepared a series of optically active helical
poly(phenylacetylene)s bearing cinchona alkaloid residues as
the pendants through an ester- or amide-linkage, such as
poly-Cd, poly-Qn, poly-ACd, and poly-AQn (Chart 1), which
possess a preferred-handed helical conformation induced by
Additional Supporting Information may be found in the online version of this article.
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CHART 1 Structures of helical poly(phenylacetylene)-based
asymmetric catalysts bearing cinchona alkaloid pendants via
an amide or ester linkage.
CHART 2 Structures of helical poly(phenylacetylene)-based
asymmetric catalysts bearing cinchona alkaloid pendants via a
sulfonamide linkage.
group5(b) and helical poly(quinoxaline)-based catalysts for
the metal-catalyzed asymmetric reactions.6(i,k,m,n) In this
study, we synthesized four novel optically active helical poly
(phenylacetylene)s bearing cinchona alkaloid pendants
through a sulfonamide linkage (poly-SCd, poly-SCn, poly-
SQn, and poly-SQd, Chart 2), and investigated their asym-
metric organocatalysis. We anticipated that the sulfonamide-
linked cinchona alkaloid-containing poly(phenylacetylene)s
might provide novel polymeric organocatalysts that can
more efficiently activate polar substrates through intermolec-
ular hydrogen bonding in diverse asymmetric transforma-
tions than the ester- and amide-linked cinchona alkaloid-
bound helical poly(phenylacetylene)s, leading to novel enan-
tioselective polymeric organocatalysts in specific asymmetric
transformations.4
RESULTS AND DISCUSSION
A series of optically active phenylacetylenes bearing cinchona
alkaloid derivatives through a sulfonamide linkage (M-SCd,
M-SCn, M-SQn, and M-SQd) were synthesized from the
amino-functionalized cinchona alkaloids (ACd, ACn, AQn,
and AQd, respectively)5(b),7 via three steps according to
Scheme 1.8 The polymerization of M-SCd was first performed
SCHEME 1 Synthetic route of monomers and polymers.
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TABLE 1 Polymerization Results of M-SCd, M-SCn, M-SQn, and M-SQda
Polymer
Mn 3 1024b
Mw/Mn
De1st (k)c
b
Entry
Monomer
Solvent
Catalyst
Code
Yield (%)
1d
2
M-SCd
M-SCd
M-SCn
M-SQn
M-SQd
DMF
[Rh(nbd)Cl]2
Rh(nbd)BPh4
Rh(nbd)BPh4
Rh(nbd)BPh4
Rh(nbd)BPh4
Poly-SCd
Poly-SCd
Poly-SCn
Poly-SQn
Poly-SQd
No reaction
–
–
–
CHCl3
CHCl3
CHCl3
CHCl3
75
77
57
78
0.77
1.5
1.5
1.2
2.7
2.5
3.0
1.8
7.3 (441)
3.0 (419)
1.9 (435)e
7.3 (413)
3
4
5f
a
c
d
e
f
Polymerized in CHCl3 at 30 ꢀC under nitrogen; [monomer] 5 0.15 M,
Measured in CH2Cl2 (0.4 mg/mL); De (M21 cm21) and k (nm).
In DMF; [monomer] 5 0.2 M, [monomer]/[Rh] 5 100.
Measured in CHCl3/CF3CH2OH (6/1, v/v, 0.02 mg/mL).
[monomer] 5 0.075 M, [monomer]/[Rh] 5 10.
[monomer]/[Rh] 5 10.
b
Determined by SEC (polystyrene standards) with CHCl3/CF3CH2OH (9/
1, v/v) containing 0.5 wt % TBAB as the eluent.
in dimethylformamide (DMF) in the presence of triethyl-
amine (NEt3) using [Rh(nbd)Cl]2 (nbd: norbornadiene) as
the catalyst (Entry 1, Table 1), which had been used to poly-
merize the phenylacetylenes bearing ester- and amide-linked
cinchona alkaloid derivatives, producing high-molecular-
weight poly(phenylacetylene)s.5(a,b) However, the polymeriza-
tion did not take place at all. We then used a cationic rho-
dium catalyst (Rh(nbd)BPh4), which has been reported to be
effective for the polymerization of sulfonamide-containing
phenylacetylene derivatives.9 The cationic Rh catalyst poly-
merized M-SCd, M-SCn, M-SQn, and M-SQd, affording rela-
its poor solubility in common organic solvents in the ab-
sence of CF3CH2OH. All of the polymers showed Cotton
effects biased by the optically active cinchona alkaloid
pendants in the long absorption regions of the p-conjugated
polymer backbones being different from those of the corre-
sponding monomers (Supporting Information Fig. S4),
whereas the CD intensities of poly-SCn and poly-SQn were
much lower than the other polymers (Fig. 1). The induced
CD intensities of poly-SCd, poly-SCn, and poly-SQd increased
with the decreasing temperature owing to the dynamic heli-
cal conformational characteristic of the poly(phenylacety-
lene)s although poly-SQn showed almost no temperature
dependency between 55 and 0 ꢀC (Supporting Information
Fig. S5).11 Poly-SCd (a) and poly-SCn (b) [Fig. 1(A)] and also
poly-SQn (i) and poly-SQd (j) [Fig. 1(B)] exhibited the same
positive first Cotton effect signs in the main-chain regions,
whereas the CD spectral patterns of the corresponding ester-
and amide-linked cinchona alkaloid-containing poly(phenyla-
cetylene)s were opposite (mirror image) to each other owing
to their pseudoenantiomeric relationships (Cd/Cn and Qn/
Qd).5(a,b) The exact helical structures including the helical
sense and pitch remain unclear, but the obviously different
tively high molecular weight (Mn 5 0.77–1.5
3
104)
poly(phenylacetylene)s in moderate yields (57–78%)
(Entries 2–5, Table 1). The cis-transoidal structures of the
polymers were confirmed by laser Raman spectroscopy
(Supporting Information Fig. S3)5,10 because their 1H NMR
spectra were too broad to investigate the main-chain struc-
tures (Supporting Information Figs. S1 and S2).
Figure 1 shows the circular dichroism (CD) and absorption
spectra of the poly(phenylacetylene)s measured in CH2Cl2,
except for poly-SQn [CHCl3/CF3CH2OH (6/1, v/v)] because of
FIGURE 1 CD and absorption spectra of (A) poly-SCd (a, e), poly-SCn (b, f), and poly-SCd (c, g) and poly-SCn (d, h) after grinding
for 20 min, measured in CH2Cl2 (0.4 mg/mL), and (B) poly-SQn (i, k) and poly-SQd (j, l) in CHCl3/CF3CH2OH (6/1, v/v, 0.02 mg/mL)
and CH2Cl2 (0.4 mg/mL) at 25 ꢀC, respectively.
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TABLE 2 Enantioselective Henry Reaction of 9 with Nitrometha-
counterparts (up to 97% ee) (Entries 2, 4, 6, and 8), giving
12 with the same absolute configurations as the polymers,
indicating the negative effect of the helical scaffold on the
present enantioselective methanolysis12; in other words, the
enantioselectivities were largely governed by the chiral cin-
chona alkaloid residues. The amide- and ester-linked poly-
mers (poly-AQn and poly-Qn) exhibited relatively lower
enantioselectivities and reactivities than those catalyzed by
the corresponding sulfonamide-linked helical polymer (poly-
SQn) (Entries 5, 9, and 10), suggesting that the sulfonamide
functionality remarkably enhanced the reactivity and enan-
tioselectivity through the intermolecular hydrogen bonding
with the polar substrate 11.
nea
Entry
Catalyst
Yield (%)b
ee (%)c
1
Poly-SQn
M-SQn
48
88
77
10
<5
2
<5
3d
4d
Poly-AQn
Poly-Qn
94 (R)
<5
Interestingly, we found a remarkable enhancement of the
enantioselectivities of the sulfonamide-linked helical poly-
mers than those of the corresponding monomers in the
asymmetric aza-Michael addition of anilines (13) to chalcone
(14). Although the catalytic asymmetric aza-Michael addi-
tions of aromatic amines have been developed using transi-
tion metal-based catalysts and organocatalysts since the first
report by Jïrgensen in 2001,13,14 the development of highly
enantioselective methods is still one of the major challenges
in organic synthesis and asymmetric catalysis.15,16 Table 4
summarizes the resultsꢀof the asymmetric aza-Michael addi-
tion of 13 to 14 at 25 C using the sulfonamide-linked heli-
cal polymers and the corresponding monomers under a
solvent-free condition. For comparison, the results using the
a
The reactions of 9 (0.3 M) with nitromethane (10 equiv) were carried
out in the presence of catalyst (20 mol %) in CHCl3/CF3CH2OH (6/1, v/v)
at 220 ꢀC for 7 days. The catalyst loading of the polymers is calculated
based on the monomer units.
b
Isolated yield.
c
Determined by chiral HPLC analysis.
Data were cited from ref. 4(b).
d
CD and absorption spectral patterns between poly-SCd/poly-
SCn and poly-SQn/poly-SQd suggest that their helical struc-
tures are likely different from each other probably owing to
the more bulky sulfonamide linkages than the ester and am-
ide ones.
We then investigated the catalytic activities and enantioselec-
tivities of the sulfonamide-linked helical polymers and mono-
mers in some asymmetric transformations. Table
2
summarizes the results of the asymmetric Henry reaction of
4-nitrobenzaldehyde (9) with nitromethane in CHCl3/
CF3CH2OH (6/1, v/v) at 220 ꢀC, where the Qn-derived am-
ide-linked helical polymer (poly-AQn) showed an excellent
enantioselectivity (94% ee, Entry 3, Table 2) as reported
previously.5(b) In contrast, the corresponding sulfonamide-
linked poly-SQn and its monomer (M-SQn) exhibited poor
enantioselectivities (Entries 1 and 2) as observed for the
ester-linked polymer (poly-Qn) (Entry 4).5(b) These results
clearly indicated that the linkage of the cinchona alkaloid-
containing poly(phenylacetylene)-based organocatalysts plays
TABLE 3 Enantioselective Desymmetrization of Prochiral Cyclic
Anhydride 11a
Entry
Catalyst
Yield (%)b
ee (%)c
1
2
Poly-SCd
M-SCd
98
81 (1S,2R)
97 (1S,2R)
66 (1R,2S)
84 (1R,2S)
86 (1S,2R)
97 (1S,2R)
65 (1R,2S)
90 (1R,2S)
53 (1S,2R)
29 (1S,2R)
86
a
crucial role in their enantioselectivities as well as
3
Poly-SCn
M-SCn
89
reactivities.
4
>99
>99
>99
>99
>99
94
5
Poly-SQn
M-SQn
We next examined the asymmetric organocatalysis of the sul-
fonamide-linked helical polymers in the methanolytic desym-
metrization of cyclic anhydride 11 in 2-methoxy-2-
methylpropane (MTBE) at room temperature, because small
cinchona alkaloid-based sulfonamide catalysts have been
proved useful.4(b,d,e,g) The results are summarized in Table 3
together with those using the corresponding monomers and
the amide- (poly-AQn) and ester- (poly-Qn) linked helcial
poly(phenylacetylene)s as catalysts. All of the sulfonamide-
linked helical polymers promoted the methanolysis of 11,
yielding the optically active 12 in good yields and enantio-
selectivities (up to 86% ee) (Entries 1, 3, 5, and 7). However,
the observed enantioselectivities of the polymers were
slightly lower than those catalyzed by the monomeric
6
7
Poly-SQd
M-SQd
8
9
Poly-AQn
Poly-Qn
10
83
a
The reactions of 11 (0.05 M) with methanol (10 equiv) were carried out
in the presence of catalyst (10 mol %) in MTBE at room temperature for
24 h. The polymer catalysts were almost insoluble in the solvent. The
catalyst loading of the polymers is calculated based on the monomer
units.
b
Isolated yield.
c
Determined by Chiral HPLC analysis of the corresponding 4-bromo-
phenyl ester derived from 12 (EXPERIMENTAL).
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TABLE 4 Asymmetric Aza-Michael Addition of 13 to 14a
reactivities in comparison to the corresponding sulfonamide-
linked poly-SCd (Entries 1, 11, and 12). The pseudoenantio-
meric pairs of the helical polymers, poly-SCd/poly-SCn and
poly-SQn/poly-SQd, gave 15 with opposite absolute configu-
rations (Entries 1, 4, 7, and 9) although all of these polymers
showed the same positive first Cotton effect signs (a, b, i,
and j in Fig. 1). The enantioselectivity of poly-SQn (51% ee)
was better than that of poly-SQd (38% ee), whereas poly-
SQn exhibited a relatively lower CD intensity in the main-
chain chromophore region compared with that of poly-SQd
[Fig. 1(B)]. As a result, the Cotton effect signs and CD inten-
sities of the sulfonamide-linked poly(phenylacetylene)s that
generally correspond to the helical handedness (right- or
left-handed helix) and its excess of the polymers, respec-
tively, appear to have little relation to the enantioselectivity
of the present asymmetric aza-Michael addition. However,
the fact that a remarkable enhancement of the enantioselec-
tivities of the sulfonamide-linked helical polymers than those
of the corresponding monomers and nonhelical polymers
was observed in the asymmetric aza-Michael addition
suggests that an ordered main-chain structure including a
helical conformation may assist regular arrangements of the
catalytically active pendant residues, thereby leading to a re-
markable enhancement of the enantioselectivity.
Entry
Catalyst
Yield (%)b
ee (%)c
1
Poly-SCd
Poly-SCdd
M-SCd
92
87
98
95
79
98
99
>99
87
92
87
69
86 (S)
<5
2
3
<5
4
Poly-SCn
Poly-SCnd
M-SCn
69 (R)
25 (R)
43 (R)
51 (S)
<5
5
6
7
Poly-SQn
M-SQn
8
9
Poly-SQd
M-SQd
38 (R)
58 (R)
27 (R)
<5
10
11
12
Poly-ACd
Poly-Cd
a
The reaction of 14 (0.5 M) was carried out in the presence of catalyst
(30 mol %) in 13 (20 equiv) as a solvent at 25 ꢀC for 6 days. The poly-
mer catalysts were almost insoluble. The catalyst loading of the poly-
mers is calculated based on the monomer units.
b
EXPERIMENTAL
Isolated yield.
Determined by chiral HPLC analysis.
c
d
Materials
Polymers were grinded for 20 min before use.
All starting materials were purchased from Aldrich (Milwau-
kee, WI), Wako Pure Chemical Industries (Osaka, Japan), or
Tokyo Kasei (TCI, Tokyo, Japan) and were used as received,
except for NEt3, CHCl3, and DMF. NEt3 was dried over KOH
pellets and distilled onto KOH under nitrogen. CHCl3 was
dried over calcium hydride (CaH2), distilled, and stored
under nitrogen. DMF was dried and deoxygenized by passing
through purification columns (Glass Contour Solvent System,
Nikko Hansen, Osaka, Japan) before use. NEt3 and CHCl3
were redistilled from KOH and CaH2, respectively, under high
vacuum just before polymerization. Anhydrous THF (water
content, <0.005%) was purchased from Wako (Osaka,
Japan). Poly-Cd,5(a) poly-Qn,5(a) ACd,5(b) ACn,5(b) AQn,5(b)
amide- and ester-linked helical poly(phenylacetylene)s (poly-
ACd and poly-Cd) are also shown.
For the asymmetric aza-Michael addition of 13 to 14, poly-
SCd gave the S-enriched 15 with a high enantioselectivity
(86% ee) that was significantly higher than that catalyzed by
the corresponding monomer M-SCd (<5% ee) (Entries 1 and
3), indicating the remarkable positive effect of the macromo-
lecular helicity on the enantioselectivity in the present cata-
lytic system. A similar enhancement of the enantioselectivity
was also observed for poly-SCn and poly-SQn (Entries 4,
6–8), whereas the helical structure of poly-SQd (38% ee)
showed a negative effect, giving a lower enantioselectivity
than that catalyzed by M-SQd (58% ee) (Entries 9 and 10).
Such a synergistic effect on the enantioselectivity and impor-
tance of the induced helical chirality were unambiguously
proved by the facts that the nonhelical (trans-enriched) poly-
SCd and poly-SCn showed very poor enantioselectivities (<5
and 25% ee, respectively) prepared by grinding the as-pre-
pared cis-poly-SCd and poly-SCn (Entries 2 and 5), because
the polymers almost lost their helical conformations, result-
ing in the disappearance of the CD in the polymer backbone
regions (c and d, Fig. 1A).5,10 The acidic sulfonamide func-
tionality also contributed to the present aza-Michael reaction
via intermolecular hydrogen bonds between the sulfonamide
residues and the carbonyl group of chalcone,4(b,e) because
the amide- and ester-linked polymers (poly-ACd and poly-
Cd) exhibited relatively lower enantioselectivities and
AQd,5(b) poly-ACd,5(b) poly-AQn,5(b) and Rh(nbd)BPh4 were
17
prepared according to the previously reported methods.
Instruments
The melting points were measured on a Yanako melting
point apparatus (Yanako, Kyoto, Japan) and were uncor-
rected. The NMR spectra were measured using a Varian VXR-
500S spectrometer (Varian, Palo Alto, CA) operating at 500
MHz for 1H and 125 MHz for 13C using tetramethylsilane or
a solvent residual peak as the internal standard. The infrared
(IR) spectra were recorded on a JASCO FT/IR-680 spectro-
photometer (JASCO, Tokyo, Japan). The absorption and CD
spectra were obtained in a 0.1 or 1.0 cm quartz cell using a
JASCO V570 spectrophotometer and a JASCO J-820 spectro-
polarimeter, respectively. The temperature was controlled
with a JASCO PTC-423L apparatus. The concentrations of the
polymers were calculated based on the monomer units. Size
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exclusion chromatography (SEC) measurements were per-
formed with a JASCO PU-980 liquid chromatograph equipped
with a UV–visible detector (JASCO UV-1570, 254 nm) and a
column oven (JASCO CO-1565). The number-average molecu-
lar weight (Mn) and its distribution (Mw/Mn) were deter-
mined at 40 ꢀC using a Tosoh TSKgel MultiporeHXL-M (30
cm) SEC column (Tosoh, Tokyo, Japan), and CHCl3/CF3CH2OH
(9/1, v/v) containing 0.5 wt % tetra-n-butylammonium bro-
mide (TBAB) was used as the eluent at a flow rate of 0.5
mL/min. The molecular weight calibration curve was
obtained with polystyrene standards (Tosoh). The chiral
HPLC analyses were performed on a JASCO PU-2080 Plus liq-
uid chromatograph equipped with a Multi UV–visible detec-
tor (JASCO MD-2010 Plus) and an optical rotation detector
(JASCO OR-2090 Plus, Hg–Xe without filter) using a Chiral-
pak AD-H or Chiralcel OD column (0.46 (i.d.) 3 25 cm, Dai-
cel). A 2-propanol/n-hexane mixture was used as the eluent.
Recycling preparative SEC was performed with an LC-908W-
C60 liquid chromatograph (JAI, Tokyo, Japan) equipped with
UV–visible (JAI UV-3702) and RI (JAI RI-5) detectors. SEC
columns, JAIGEL-1H, and JAIGEL-2H (60 3 4 cm (i.d.)) were
connected in series, and CHCl3 was used as the eluent. The
electron spray ionization mass spectra (ESI-MS) were
recorded using a JEOL JMS-T100CS spectrometer (JEOL,
Akishima, Japan). The laser Raman spectra were taken on a
JASCO RMP-200 spectrophotometer.
Spectroscopic data of 3. Yield: 79%. Mp 5 102–104 ꢀC. IR
(film, cm21): 3179 (NAH), 1334 (S@O), 1167 (S@O). 1H
NMR (500 MHz, THF-d8, d, ppm): 8.71 (d, J 5 4.5 Hz, 1H, Ar),
8.19–7.93 (m, 1H, Ar), 7.79–7.12 (m, 8H, Ar), 6.79 (bs, 1H,
ANHCHA), 5.92–5.77 (m, 1H, ACH@CH2), 5.08 (d, J 5 9.0
Hz, 1H, ANHCHA), 5.03–4.89 (m, 2H, ACH@CH2), 3.00–2.79
(m, 3H), 2.76–2.66 (m, 1H), 2.58–2.30 (m, 1H), 2.26–2.17
(m, 1H), 1.62–1.39 (m, 3H), 1.32–1.10 (m, 1H), 0.86–0.72
(m, 1H). 13C NMR (125 MHz, THF-d8, d, ppm): 150.6, 141.3,
138.5, 132.6, 132.1, 131.4, 129.4, 129.2, 128.9, 127.1, 123.2,
120.7, 114.6, 99.9, 61.9, 49.5, 47.1, 39.9, 38.1, 28.6, 27.9,
27.1. HRMS (ESI1, m/z): calcd for C25H26IN3O2S, 560.0869;
found, 560.0893 [M1H]1.
ꢀ
Spectroscopic data of 5. Yield: 88%. Mp 5 90–92 C. IR (film,
cm21): 3214 (NAH), 1336 (S@O), 1158 (S@O). 1H NMR
(500 MHz, THF-d8, d, ppm): 8.61–8.48 (m, 1H, Ar), 7.99–7.80
(m, 1H, Ar), 7.61 (d, J 5 7.6 Hz, 1H, Ar), 7.55–7.42 (m, 1H,
Ar), 7.40–6.98 (m, 5H, Ar), 6.78 (bs, 1H, ANHCH@), 5.82–
5.63 (m, 1H, ACH@CH2), 5.08–4.79 (m, 3H, ANHCHA,
ACH@CH2), 4.01–3.80 (m, 3H, AOCH3), 3.29–3.09 (m, 1H),
3.02–2.92 (m, 1H), 2.90–2.80 (m, 1H), 2.77–2.54 (m, 2H),
2.25 (bs, 1H), 1.65–1.48 (m, 3H), 1.34–1.18 (m, 1H), 1.03–
0.73 (m, 1H). 13C NMR (125 MHz, THF-d8, d, ppm): 158.8,
148.0, 143.8, 142.4, 141.8, 138.2, 137.7, 132.7, 129.2, 129.0,
121.8, 120.8, 114.3, 101.4, 99.6, 61.6, 57.0, 56.4, 55.6, 53.3,
41.0, 40.8, 28.6, 26.5. HRMS (ESI1, m/z): calcd for
Synthesis of Compounds 1, 3, 5, and 7
C
26H28IN3O3S, 590.0974; found, 590.1003 [M1H]1.
A typical procedure for the synthesis of 1 is described
(Scheme 1). To a stirred mixture of ACd (1.47 g, 5.00 mmol)
in CH2Cl2 (15.0 mL) and NEt3 (1.40 mL), a solution of 4-
iodobenzenesulfonyl chloride (1.66 g, 5.50 mmol) was slowly
added in CH2Cl2 (5.0 mL) under a nitrogen atmosphere, and
the reaction mixture was stirred at room temperature over-
night. After the addition of water (30 mL), the mixture was
extracted with CH2Cl2 (40 mL 3 6) and the organic extracts
were dried over anhydrous Na2SO4. After filtration, the sol-
vent was removed by evaporation and the residue was puri-
fied by column chromatography (SiO2, n-hexane/EtOAc 5 1/
2-0/1, v/v) to afford 1 (2.30 g, 82% yield) as a white solid.
ꢀ
Spectroscopic data of 7. Yield: 64%. Mp 5 90–91 C. IR (film,
cm21): 3180 (NAH), 1332 (S@O), 1169 (S@O). H NMR (500
1
MHz, THF-d8, d, ppm): 8.56 (d, J 5 4.5 Hz, 1H, Ar), 7.94–7.87
(m, 1H, Ar), 7.75 (d, J 5 8.0 Hz, 2H, Ar), 7.66–7.12 (m, 5H, Ar),
6.76 (bs, 1H, ANHCHA), 5.93–5.80 (m, 1H, ACH@CH2), 5.07
(d, J 5 10.6 Hz, 1H, ANHCHA), 4.96–4.83 (m, 2H, ACH@CH2),
4.01–3.80 (m, 3H, AOCH3), 2.97–2.70 (m, 4H), 2.41–2.36 (m,
1H), 2.22 (bs, 1H), 1.60–1.41 (m, 3H), 1.21–1.12 (m, 1H),
0.87–0.82 (m, 1H). 13C NMR (125 MHz, THF-d8, d, ppm):
158.7, 148.0, 144.3, 141.7, 138.5, 132.7, 132.1, 129.6, 129.2,
129.0, 122.2, 120.9, 114.5, 100.8, 99.9, 61.8, 55.6, 55.5, 52.9,
49.5, 46.9, 39.4, 28.5, 27.2. HRMS (ESI1, m/z): calcd for
Mp 5 97–99 ꢀC. IR (film, cm21): 3199 (NAH), 1336 (S@O),
1158 (S@O). 1H NMR (500 MHz, THF-d8, d, ppm): 8.67 (bs,
1H, Ar), 8.37–8.19 (m, 1H, Ar), 8.09–7.92 (m, 1H, Ar), 7.74–
7.52 (m, 3H, Ar), 7.45–7.27 (m, 2H, Ar), 7.24–7.02 (m, 2H,
Ar), 6.84 (bs, 1H, ANHCHA), 5.79–5.59 (m, 1H, ACH@CH2),
5.10 (d, J 5 9.3 Hz, 1H, ANHCHA), 4.97–4.76 (m, 2H,
ACH@CH2), 3.27–3.13 (m, 1H), 2.99–2.54 (m, 4H), 2.24 (bs,
1H), 1.64–1.45 (m, 3H), 1.25–1.15 (m, 1H), 1.01–0.72 (m,
1H). 13C NMR (125 MHz, THF-d8, d, ppm): 150.5, 145.8,
142.4, 141.6, 138.3, 137.8, 131.4, 129.2, 128.4, 127.2, 123.4,
120.7, 114.3, 99.7, 61.9, 57.7, 56.4, 53.1, 41.0, 40.8, 28.6,
28.4. High-resolution mass spectrometry (HRMS) (ESI1, m/
z): calcd for C25H26IN3O2S, 560.0869; found, 560.0874
[M1H]1.
C
26H28IN3O3S, 590.0974; found, 590.0990 [M1H]1.
Synthesis of Compounds 2, 4, 6, and 8
A typical procedure for the synthesis of 2 is described
(Scheme 1). (Trimethylsilyl)acetylene (9.80 mL, 69.4 mmol)
was added to a mixture of 1 (2.30 g, 4.10 mmol), triphenyl-
phosphine (178 mg, 680 mmol), bis(triphenylphosphine)pal-
ladium dichloride (229 mg, 326 mmol), and copper (I) iodide
(187 mg, 978 mmol) in DMF (10.0 mL) and NEt3 (30.0 mL)
under a nitrogen atmosphere, and the reaction mixture was
stirred under nitrogen at room temperature overnight. After
most of the solvents were removed under reduced pressure,
the residue was added dropwise into water (300 mL). The
precipitated product was filtered, washed with water, dried
under reduced pressure, and purified by column chromatog-
raphy (SiO2, n-hexane, EtOAc/n-hexane 5 1/1-1/0, v/v) to
afford 2 (1.97 g, 91% yield) as a green solid. Mp 5 117–118
ꢀC. IR (film, cm21): 3188 (NAH), 2159 (CBC), 1325 (S@O),
The compounds (3, 5, and 7) were also prepared from ACn,
AQn, and AQd, respectively, in the same way for the synthe-
sis of 1 (Scheme 1).
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1251 (CASi), 1157 (S@O). 1H NMR (500 MHz, THF-d8, d,
ppm): 8.70 (bs, 1H, Ar), 8.23 (bs, 1H, Ar), 8.05 (bs, 1H, Ar),
7.77–7.05 (m, 7H, Ar), 6.85 (bs, 1H, ANHCHA), 5.80–5.60
(m, 1H, ACH@CH2), 5.14–4.77 (m, 3H, ACH@CH2,
ANHCHA), 3.25–3.14 (m, 1H), 2.96 (bs, 1H), 2.83–2.70 (m,
2H), 2.64–2.53 (m, 1H), 2.24 (bs, 1H), 1.62–1.41 (m, 3H),
1.25–1.12 (m, 1H), 0.94–0.77 (m, 1H), 0.24 (s, 9H,
ASi(CH3)3). 13C NMR (125 MHz, THF-d8, d, ppm): 150.5,
142.4, 132.6, 132.3, 132.1, 131.4, 129.2, 128.9, 127.8, 127.2,
123.4, 120.8, 114.4, 104.3, 97.5, 62.1, 62.0, 57.8, 56.3, 53.1,
41.0, 40.7, 28.5, 28.3, 0.4. HRMS (ESI1, m/z): calcd for
134.5, 132.6, 132.1, 129.0, 128.0, 122.2, 120.9, 114.5, 100.9,
97.6, 61.9, 55.6, 55.5, 52.9, 49.5, 47.0, 39.5, 39.4, 28.5, 27.2,
0.1. HRMS (ESI1, m/z): calcd for C31H37N3O3SSi, 560.2403;
found, 560.2384 [M1H]1.
Synthesis of Monomers (M-SCd, M-SCn, M-SQn,
and M-SQd)
A typical procedure for the synthesis of M-SCd is described
(Scheme 1). A solution of tetra-n-butylammonium fluoride in
THF (1 M, 4.00 mL, 4.00 mmol) was added to a solution of 2
(1.97 g, 3.72 mmol) in THF (50.0 mL) and methanol (5.00
mL). After stirring at room temperature overnight, the reac-
tion was quenched by the addition of a saturated NH4Cl
aqueous solution (50 mL). After the solvent was removed
under reduced pressure, water (30 mL) was added, and the
mixture was extracted with CH2Cl2 (50 mL 3 4). The organic
extracts were dried over anhydrous Na2SO4 and filtered. Af-
ter the solvent was removed by evaporation, the residue was
purified by column chromatography (SiO2, EtOAc) and recy-
cling preparative SEC to afford M-SCd (1.15 g, 68% yield) as
a green solid.
C
30H35N3O2SSi, 530.2297; found, 530.2303 [M1H]1.
The compounds (4, 6, and 8) were also prepared from 3, 5,
and 7, respectively, in the same way for the synthesis of 2
(Scheme 1).
ꢀ
Spectroscopic data of 4. Yield: 99%. Mp 5 93–94 C. IR (film,
cm21): 3180 (NAH), 2159 (CBC), 1330 (S@O), 1251 (CASi),
1165 (S@O). 1H NMR (500 MHz, THF-d8, d, ppm): 8.71 (d,
J 5 4.3 Hz, 1H, Ar), 8.20–7.98 (m, 1H, Ar), 7.74–7.21 (m, 8H,
Ar), 6.78 (bs, 1H, ANHCHA), 5.89–5.77 (m, 1H, ACH@CH2),
5.12–4.87 (m, 3H, ACH@CH2, ANHCHA), 2.99–2.79 (m, 3H),
2.76–2.69 (m, 1H), 2.58–2.35 (m, 1H), 2.25–2.16 (m, 1H),
1.59–1.37 (m, 3H), 1.22–1.04 (m, 1H), 0.85–0.71 (m, 1H),
0.25 (s, 9H, ASi(CH3)3). 13C NMR (125 MHz, THF-d8, d,
ppm): 150.5, 141.3, 132.6, 132.4, 132.1, 131.4, 129.2, 128.9,
128.0, 127.0, 123.2, 120.7, 114.6, 104.3, 97.6, 62.0, 52.6,
49.5, 47.2, 39.9, 38.1, 28.6, 27.9, 27.1, 0.1. HRMS (ESI1, m/
z): calcd for C30H35N3O2SSi, 530.2297; found, 530.2322
[M1H]1.
Mp 5 91–92 C. IR (film, cm21): 3292 (BCAH), 2108 (CBC),
ꢀ
1
1335 (S@O), 1156 (S@O). H NMR (500 MHz, DMSO-d6, 100
ꢀC, d, ppm): 8.73 (d, J 5 4.5 Hz, 1H, Ar), 8.28 (d, J 5 8.4 Hz,
1H, Ar), 7.98 (d, J 5 8.4 Hz, 1H, Ar), 7.72 (t, J 5 7.9 Hz, 1H,
Ar), 7.61 (t, J 5 7.8 Hz, 1H, Ar), 7.45 (dd, J 5 14.2, 4.5 Hz, 3H,
Ar), 7.28 (d, J 5 8.3 Hz, 2H, Ar), 5.78-5.70 (m, 1H,
ACH@CH2), 4.99–4.90 (m, 3H, ANHCHA, ACH@CH2), 4.15
(s, 1H, BCH), 3.21–3.09 (m, 2H), 2.89–2.80 (m, 1H), 2.79–
2.71 (m, 1H), 2.58–2.49 (m, 1H), 2.28–2.22 (m, 1H), 1.57–
1.41 (m, 3H), 1.16–1.08 (m, 1H), 0.71–0.66 (m, 1H). 13C
NMR (125 MHz, THF-d8, d, ppm): 150.5, 149.4, 145.7, 142.4,
141.8, 132.5, 131.4, 129.2, 128.4, 127.8, 127.2, 123.4, 120.8,
114.4, 82.8, 81.7, 61.9, 56.3, 53.1, 41.0, 40.7, 28.5, 28.3, 26.5.
HRMS (ESI1, m/z): calcd for C27H27N3O2S, 458.1902; found,
458.1910 [M1H]1. Anal. Calcd. (%) for C27H27N3O2S: C,
70.87; H, 5.95; N, 9.18. Found: C, 70.64; H, 5.93; N, 8.89.
ꢀ
Spectroscopic data of 6. Yield: 95%. Mp 5 96–99 C. IR (film,
cm21): 3218 (NAH), 2159 (CBC), 1324 (S@O), 1252 (CASi),
1156 (S@O). 1H NMR (500 MHz, THF-d8, d, ppm): 8.53 (bs,
1H, Ar), 7.99–7.81 (m, 1H, Ar), 7.72–7.62 (m, 1H, Ar), 7.51–
7.12 (m, 6H, Ar), 6.78 (bs, 1H, ANHCHA), 5.81–5.61 (m, 1H,
ACH@CH2), 5.07–4.78 (m, 3H, ANHCHA, ACH@CH2), 4.04–
3.76 (m, 3H, AOCH3), 3.26–3.09 (m, 1H), 3.00–2.90 (m, 1H),
2.81–2.70 (m, 2H), 2.64–2.46 (m, 1H), 2.23 (bs, 1H), 1.63–
1.44 (m, 3H), 1.31–1.16 (m, 1H), 0.98–0.74 (m, 1H), 0.24 (s,
9H, ASi(CH3)3). 13C NMR (125 MHz, THF-d8, d, ppm): 158.8,
148.0, 145.6, 144.0, 142.4, 135.4, 134.5, 132.6, 132.1, 129.0,
127.7, 121.7, 120.9, 114.3, 101.4, 97.5, 61.8, 56.5, 56.4, 55.6,
55.4, 53.3, 41.0, 40.7, 28.6, 26.6, 0.1. HRMS (ESI1, m/z):
The monomers (M-SCn, M-SQn, and M-SQd) were also pre-
pared from 4, 6, and 8, respectively, in the same way for the
synthesis of M-SCd (Scheme 1).
Spectroscopic data of M-SCn. Yield: 67%. Mp 5 94–96 ꢀC. IR
(film, cm21): 3291 (BCAH), 2109 (CBC), 1333 (S@O), 1165
(S@O). 1H NMR (500 MHz, DMSO-d6, 100 ꢀC, d, ppm): 8.77
(d, J 5 4.5 Hz, 1H, Ar), 8.46–8.27 (m, 1H, Ar), 8.00 (d, J 5 8.3
Hz, 1H, Ar), 7.73 (t, J 5 7.2 Hz, 1H, Ar), 7.62 (t, J 5 7.4 Hz,
1H, Ar), 7.56–7.47 (m, 3H, Ar), 7.37 (d, J 5 8.4 Hz, 2H, Ar),
5.84–5.77 (m, 1H, ACH@CH2), 5.08–4.80 (m, 3H, ACH@CH2,
ANHCHA), 4.16 (s, 1H, BCH), 3.16–3.08 (m, 1H), 2.96–2.90
(m, 1H), 2.84–2.77 (m, 1H), 2.72–2.66 (m, 1H), 2.50–2.41
(m, 1H), 2.24–2.17 (m, 1H), 1.55–1.40 (m, 3H), 0.98–0.92
(m, 1H), 0.81–0.72 (m, 1H). 13C NMR (125 MHz, THF-d8, d,
ppm): 150.4, 149.4, 146.0, 141.6, 141.3, 132.6, 131.4, 129.2,
128.0, 127.1, 127.0, 123.2, 120.7, 114.6, 82.7, 81.7, 62.0,
49.6, 47.2, 39.9, 38.1, 28.6, 27.9, 27.1. HRMS (ESI1, m/z):
calcd for C27H27N3O2S, 458.1902; found, 458.1886 [M1H]1.
calcd for
C31H37N3O3SSi, 560.2403; found, 560.2422
[M1H]1.
Spectroscopic data of 8. Yield: 69%. Mp 5 99–101 ꢀC. IR
(film, cm21): 3179 (NAH), 2159 (CBC), 1329 (S@O), 1252
(CASi), 1167 (S@O). 1H NMR (500 MHz, THF-d8, d, ppm):
8.56 (bs, 1H, Ar), 7.94–7.82 (m, 1H, Ar), 7.80–7.66 (m, 2H,
Ar), 7.57–7.17 (m, 5H, Ar), 6.77 (bs, 1H, ANHCHA), 5.90–
5.78 (m, 1H, ACH@CH2), 5.05 (d, J 5 10.5 Hz, 1H, ANHCHA),
4.94–4.85 (m, 2H, ACH@CH2), 4.04–3.78 (m, 3H, AOCH3),
2.98–2.80 (m, 3H), 2.76–2.66 (m, 1H), 2.43–2.36 (m, 1H),
2.21 (bs, 1H), 1.59–1.40 (m, 3H), 1.23–1.11 (m, 1H), 0.88–
0.79 (m, 1H), 0.25 (s, 9H, ASi(CH3)3). 13C NMR (125 MHz,
THF-d8, d, ppm): 158.7, 148.0, 145.6, 144.4, 141.5, 135.3,
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Anal. Calcd. (%) for C27H27N3O2S: C, 70.87; H, 5.95; N, 9.18.
Found: C, 70.87; H, 5.94; N, 9.10.
The concentrations of the monomer and the rhodium catalyst
were 0.15 and 0.015 M, respectively. After 24 h, triphenylphos-
phine (278 mg, 1.06 mmol) was added to the reaction mixture.
The resulting polymer (poly-SCd) was then precipitated into a
large amount of Et2O, washed with Et2O, and collected by cen-
trifugation. The product was purified by reprecipitation from
CH2Cl2 to EtOAc, and the precipitated poly-SCd was washed
with EtOAc, suspended in benzene, and freeze-dried (618 mg,
75% yield). In the similar way, poly-SCn, poly-SQn, and poly-
SQd were prepared. The Mn and Mw/Mn values of poly-SCd,
poly-SCn, poly-SQn, and poly-SQd were determined by SEC
using polystyrene standards in CHCl3/CF3CH2OH (9/1, v/v)
containing 0.5 wt % TBAB as the eluent.
Spectroscopic data of M-SQn. Yield: 46%. Mp 5 97–98 ꢀC. IR
(film, cm21): 3290 (BCAH), 2109 (CBC), 1323 (S@O), 1156
(S@O). 1H NMR (500 MHz, DMSO-d6, 100 ꢀC, d, ppm): 8.58
(d, J 5 4.5 Hz, 1H, Ar), 7.88 (d, J 5 9.0 Hz, 1H, Ar), 7.50–7.42
(m, 3H, Ar), 7.40–7.36 (m, 2H, Ar), 7.30–7.22 (m, 2H, Ar),
7.21–7.13 (m, 1H, Ar), 5.79–5.72 (m, 1H, ACH@CH2), 4.99–
4.90 (m, 3H, ANHCHA, ACH@CH2), 4.14 (s, 1H, BCH), 3.95
(s, 3H, AOCH3), 3.28–2.83 (m, 2H), 2.78–2.70 (m, 1H), 2.32
(s, 1H), 2.28–2.21 (m, 1H), 1.58–1.53 (m, 1H), 1.52–1.43 (m,
2H), 1.33–1.28 (m, 1H), 1.18–1.12 (m, 1H), 0.72–0.65 (m,
1H). 13C NMR (125 MHz, THF-d8, d, ppm): 158.8, 143.8,
142.4, 141.9, 132.7, 132.4, 132.0, 127.9, 127.6, 127.0, 121.8,
121.2, 121.0, 114.4, 101.4, 82.8, 81.7, 79.3, 61.7, 56.3, 55.6,
53.3, 41.0, 40.7, 28.5, 28.3. HRMS (ESI1, m/z): calcd for
Spectroscopic data of poly-SCd. IR (film, cm21): 3188 (NAH),
1324 (S@O), 1158 (S@O). 1H NMR (500 MHz, CDCl3/
ꢀ
CF3CD2OD (31/1, v/v), 55 C, d, ppm): 9.04–8.42 (m, 2H, Ar),
C
28H29N3O3S, 488.2008; found, 488.1991 [M1H]1. Anal.
8.25–8.00 (m, 1H, Ar), 7.90–6.95 (m, 7H, Ar), 6.50 (s, 1H,
ANHCHA), 5.70 (s, 1H, ACH@CH2), 5.25–4.62 (m, 3H,
ANHCHA, ACH@CH2), 3.38–2.98 (m, 1H), 2.74 (s, 1H), 2.52–
1.98 (m, 5H), 1.80–0.78 (m, 5H). Anal. Calcd. (%) for
(C27H27N3O2S)n: C, 70.87; H, 5.95; N, 9.18. Found: C, 70.87; H,
5.95; N, 9.15.
Calcd. (%) for C28H29N3O3S: C, 68.97; H, 5.99; N, 8.62.
Found: C, 68.79; H, 5.86; N, 8.42.
Spectroscopic data of M-SQd. Yield: 55%. Mp 5 94–97 ꢀC. IR
(film, cm21): 3290 (BCAH), 2107 (CBC), 1330 (S@O), 1166
(S@O). 1H NMR (500 MHz, DMSO-d6, 100 ꢀC, d, ppm): 8.62
(d, J 5 4.5 Hz, 1H, Ar), 7.90 (d, J 5 9.3 Hz, 1H, Ar), 7.66–7.58
(m, 2H, Ar), 7.56–7.50 (m, 3H, Ar), 7.46–7.35 (m, 3H, Ar),
5.85–5.78 (m, 1H, ACH@CH2), 5.07–4.72 (m, 3H, ANHCHA,
ACH@CH2), 4.17 (s, 1H, BCH), 3.95 (s, 3H, AOCH3), 3.20–
3.08 (m, 1H), 2.96–2.88 (m, 1H), 2.86–2.68 (m, 2H), 2.50–
2.39 (m, 1H), 2.25–2.19 (m, 1H), 1.56–1.52 (m, 1H), 1.49–
1.43 (m, 2H), 1.02–0.95 (m, 1H), 0.85–0.78 (m, 1H). 13C
NMR (125 MHz, THF-d8, d, ppm): 158.7, 148.0, 145.6, 144.4,
141.6, 135.3, 134.5, 132.7, 132.1, 129.0, 128.1, 122.2, 120.9,
114.5, 100.8, 82.7, 81.9, 61.8, 55.6, 55.5, 52.8, 49.5, 46.9,
39.4, 28.5, 27.1. HRMS (ESI1, m/z): calcd for C28H29N3O3S,
488.2008; found, 488.2016 [M1H]1. Anal. Calcd. (%) for
Spectroscopic data of poly-SCn. IR (film, cm21): 3183
(NAH), 1327 (S@O), 1157 (S@O). 1H NMR (500 MHz,
CDCl3/CF3CD2OD (31/1, v/v), 55 ꢀC, d, ppm): 8.55 (s, 2H,
Ar), 8.22–7.80 (m, 2H, Ar), 7.68–6.96 (m, 6H, Ar), 6.51 (s,
1H, ANHCHA), 5.64 (s, 1H, ACH@CH2), 5.35–4.48 (m, 3H,
ANHCHA, ACH@CH2), 3.20–2.42 (m, 2H), 2.30–1.87 (m,
5H), 1.68–0.62 (m, 5H). Anal. Calcd. (%) for (C27H27N3O2S)n:
C, 70.87; H, 5.95; N, 9.18. Found: C, 70.90; H, 5.93; N, 9.15.
Spectroscopic data of poly-SQn. IR (film, cm21): 3203
(NAH), 1321 (S@O), 1156 (S@O). 1H NMR (500 MHz,
CDCl3/CF3CD2OD (31/1, v/v), 55 ꢀC, d, ppm): 8.70–8.22 (m,
1H, Ar), 8.11–7.65 (m, 2H, Ar), 7.58–6.78 (m, 6H, Ar), 6.52
(bs, 1H, ANHCHA), 5.86–5.40 (m, 1H, ACH@CH2), 5.28–4.65
(m, 3H, ANHCHA, ACH@CH2), 4.18–3.46 (m, 3H, AOCH3),
3.39–3.02 (m, 1H), 2.90–2.51 (m, 1H), 2.40–1.90 (m, 5H),
1.78–0.70 (m, 5H). Anal. Calcd. (%) for (C28H29N3O3S)n: C,
68.97; H, 5.99; N, 8.62. Found: C, 68.95; H, 5.85; N, 8.63.
C28H29N3O3S: C, 68.97; H, 5.99; N, 8.62. Found: C, 68.95; H,
5.85; N, 8.61.
Polymerization
Polymerizations of M-SCd, M-SCn, M-SQn, and M-SQd were
carried out according to Scheme 1 in a dry glass ampule
under a dry nitrogen atmosphere using Rh(nbd)BPh4 as a
catalyst in a similar way as reported previously.5 The poly-
merization of M-SCd was first performed using [Rh(nbd)Cl]2
as a catalyst in DMF, but the polymerization did not occur at
all. The reason is not clear at present because the
[Rh(nbd)Cl]2 catalyst has been widely used to polymerize
phenylacetylenes bearing a variety of functional pendants
linked through ester and amide linkages.5,11 The polymeriza-
tion results are summarized in Table 1.
Spectroscopic data of poly-SQd. IR (film, cm21): 3174
(NAH), 1329 (S@O), 1164 (S@O). 1H NMR (500 MHz,
CDCl3/CF3CD2OD (31/1, v/v), 55 ꢀC, d, ppm): 8.72–8.27 (m,
1H, Ar), 8.05–7.70 (m, 2H, Ar), 7.65–6.90 (m, 6H, Ar), 6.80
(s, 1H, ANHCHA), 5.96–5.51 (m, 1H, ACH@CH2), 5.35–4.74
(m, 3H, ANHCHA, ACH@CH2), 4.06–3.50 (m, 3H, AOCH3),
2.98–2.48 (m, 2H), 2.37–1.92 (m, 5H), 1.72–0.60 (m, 5H).
Anal. Calcd. (%) for (C28H29N3O3S)n: C, 68.97; H, 5.99; N,
8.62. Found: C, 68.94; H, 5.95; N, 8.56.
The monomer M-SCd (824 mg, 1.80 mmol) was placed in a
dry ampule, which was then evacuated on a vacuum line and
flushed with dry nitrogen. After this evacuation–flush proce-
dure was repeated for three times, a three-way stopcock was
attached to the ampule and freshly distilled CHCl3 (5.00 mL)
was added with a syringe. To this, a solution of Rh(nbd)BPh4
Typical Procedure for Enantioselective Henry Reaction
of 9 with Nitromethane
In a glass reactor, a mixture of poly-SQn (9.8 mg, 0.020
mmol) and 9 (15.1 mg, 0.100 mmol) in CHCl3 (300 mL) and
CF3CH2OH (50 mL) was stirred at 220 ꢀC for 30 min. To
this, nitromethane (54.2 mL, 1.00 mmol) was added, and the
ꢀ
(0.0257 M) was added in distilled CHCl3 (7.00 mL) at 30 C.
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SCHEME 2 Conversion of 12 to 12a.
ꢀ
mixture was stirred at 220 C for 7 days. The reaction mix-
ture was directly subjected to flash column chromatography
(SiO2, EtOAc/n-hexane 5 1/4, v/v) to give 2-nitro-1-(4-nitro-
phenyl)ethanol (10) (10.1 mg, 48%) as a white solid.18 The
ee was determined to be <5% by chiral HPLC analysis (Chir-
alcel OD column, 2-propanol/n-hexane 5 1/9 v/v, 1.0 mL/
min, k 5 254 nm).
Hz, 2H, Ar), 3.70 (s, 3H), 3.06–2.98 (m, 2H), 2.16–2.03 (m,
2H), 1.96–1.89 (m, 2H), 1.82–1.61 (m, 2H), 1.58–1.41 (m,
2H).
In the same way, other polymers and monomers were also
employed as catalysts for the enantioselective desymmetriza-
tion. These results are summarized in Table 3.
t
(R) 5 32.7 min, t(S) 5 42.0 min. IR (KBr, cm21): 3520 (OAH),
Typical Procedure for Asymmetric Aza-Michael Addition
of 13 to 14
1556 (N@O), 1520 (N@O), 1381 (N@O), 1348 (N@O), 1086
(CAO). 1H NMR (500 MHz, CDCl3, d, ppm): 8.28 (d, J 5 9.1 Hz,
2H, Ar), 7.63 (d, J 5 9.1 Hz, 2H, Ar), 5.63–5.60 (m, 1H,
ACHOH), 4.63–4.55 (m, 2H, ACH2NO2), 3.12 (s, 1H, ACHOH).
In a glass reactor, to a mixture of 14 (20.8 mg, 0.100 mmol)
and poly-SCd (13.7 mg, 0.0300 mmol) 13 (186 mg, 2.00
mmol) was added, and the mixture was stirred at 25 ꢀC for
6 days. The reaction mixture was directly subjected to flash
column chromatography (SiO2, EtOAc/n-hexane 5 1/10, v/v)
to give 1,3-diphenyl-3-(phenylamino)propan-1-one (15)
(27.6 mg, 92%) as a white solid.15 The ee was determined
to be 86% by chiral HPLC analysis (Chiralpak AD-H column,
2-propanol/n-hexane 5 5/95 v/v, 1.0 mL/min, k 5 254 nm).
In the same way, other polymers and monomers were also
employed as catalysts for the enantioselective Henry reac-
tion. These results are summarized in Table 2.
Typical Procedure for Enantioselective
Desymmetrization of Prochiral Cyclic Anhydride 11 with
Methanol
t
(R) 5 20.1 min, t(S) 5 22.3 min. IR (film, cm21): 3384 (NAH),
1670 (C@O). 1H NMR (500 MHz, CDCl3, d, ppm): 7.91 (d,
J 5 7.7 Hz, 2H, Ar), 7.56 (t, J 5 7.4 Hz, 1H, Ar), 7.46–7.42 (m,
4H, Ar), 7.32 (t, J 5 7.6 Hz, 2H, Ar), 7.26–7.22 (m, 1H, Ar),
7.08 (t, J 5 7.0 Hz, 2H, Ar), 6.66 (t, J 5 7.3 Hz, 1H, Ar), 6.56
(d, J 5 8.6 Hz, 2H, Ar), 5.00 (dd, J 5 7.5, 5.4 Hz, 1H, ACHA),
4.55 (bs, 1H, ANHA), 3.51 (dd, J 5 16.1, 5.2 Hz, 1H,
ACH2A), 3.42 (dd, J 5 16.1, 7.7 Hz, 1H, ACH2A).
Methanol (40.5 mL, 1.00 mmol) was added dropwise to a so-
lution of 11 (15.4 mg, 0.100 mmol) and poly-SCd (4.6 mg,
0.010 mmol) in MTBE (2 mL) at room temperature under
stirring, and the mixture was stirred at room temperature
for 24 h. The reaction mixture was directly subjected to col-
umn chromatography (SiO2, Et2O) to give the hemiester
product (12) (18.2 mg, 98%) as a white solid.4(b,d,e)
1H NMR (500 MHz, CDCl3, d, ppm): 3.68 (s, 3H), 2.85 (bs, 2H),
2.10–1.94 (m, 2H), 1.82–1.73 (m, 2H), 1.61–1.38 (m, 4H).
In the same way, other polymers and monomers were also
employed as catalysts for the asymmetric aza-Michael addi-
tion. These results are summarized in Table 4.
To determine the ee, 12 was converted to the corresponding
4-bromophenyl ester 12a according to the literature proce-
dure (Scheme 2).19
CONCLUSIONS
We have prepared four novel optically active, cis-transoidal
helical poly(phenylacetylene)s bearing cinchona alkaloid
pendants through a sulfonamide linkage (poly-SCd, poly-SCn,
poly-SQn, and poly-SQd) and used as polymeric organocata-
lysts for some enantioselective reactions. We found that
among the helical polymers synthesized, poly-SCd catalyti-
cally produced the corresponding product with a remarkably
higher enantioselectivity (86% ee) than that catalyzed by the
monomeric counterpart (<5% ee) in the asymmetric aza-Mi-
chael addition reaction. The drastic enhancement of the
enantioselectivity can be ascribed to the preferred-handed
helical conformation induced in the polymer backbone, as
supported by the fact that the corresponding nonhelical
poly-SCd exhibited a negligible enantioselectivity (<5% ee).
The sulfonamide-linked poly-SCd showed a relatively higher
enantioselectivity and reactivity in comparison to the
To a solution of 12 (18.6 mg, 0.100 mmol) and 4-bromophe-
nol (34.6 mg, 0.200 mmol) in CH2Cl2 (2 mL) at 0 ꢀC, N,N0-
dicyclohexylcarbodiimide (41.3 mg, 0.200 mmol) and 4-
dimethylaminopyridine (DMAP, 6.10 mg, 0.0500 mmol) were
added. The mixture was allowed to warm to room tempera-
ture and stirred overnight. The white solid was filtered off
and the solvent was removed in vacuo. The residue was then
purified by column chromatography (SiO2, EtOAc/n-
hexane 5 1/5, v/v) to afford 12a (33.5 mg, 98% based on
12) as a colorless oil.19 The ee of 12 was determined to be
81% by chiral HPLC analysis of the obtained 4-bromophenyl
ester 12a (Chiralpak AD-H column, 2-propanol/n-
hexane 5 1/9 v/v, 1.0 mL/min, k 5 220 nm).
t
(1S,2R) 5 7.8 min, t(1R,2S) 5 8.3 min. 1H NMR (500 MHz,
CDCl3, d, ppm): 7.47 (d, J 5 8.9 Hz, 2H, Ar), 6.97 (d, J 5 8.9
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5 (a) G. M. Miyake, H. Iida, H.-Y. Hu, Z. Tang, E. Y. X. Chen, E.
Yashima, J. Polym. Sci. Part A: Polym. Chem. 2011, 49, 5192–
5198; (b) Z. Tang, H. Iida, H.-Y. Hu, E. Yashima, ACS Macro
Lett. 2012, 1, 261–265; (c) Y. Naito, Z. Tang, H. Iida, T. Miyabe,
E. Yashima, Chem. Lett. 2012, 41, 809–811.
corresponding amide- and ester-linked poly(phenylacety-
lene)s, and thus revealing the cooperative catalysis of the
sulfonamide-linkage in the present asymmetric transforma-
tion. In general, conventional helical polymer-based asym-
metric catalysts possess the catalytic units at the pendant
groups, which are located far from the helical polymer back-
bones,6 and thus the major drawback is that the catalytic
sites existing at the exterior of the helical backbones may
show their catalytic activities similar to those of their mono-
meric counter parts. In contrast, the bifunctional catalytic
sites of the present polymer catalysts seem to be located in-
terior surrounded by the helically arranged bulky cinchona
alkaloid pendants, so that the inner sulfonamide linkage
itself could play a role in the binding and activation of the
substrates as an efficient hydrogen-bond-donor catalyst. This
study suggests that the rational design of the bifunctional or
multifunctional organocatalytic residues specifically located
interior with a controlled helical sense will provide more ef-
ficient asymmetric polymeric organocatalysts for a number
of enantioselective reactions through activating a wide class
of functional substrates.
6 (a) F. Sanda, H. Araki, T. Masuda, Chem. Lett. 2005, 34, 1642–
1643; (b) K. Maeda, K. Tanaka, K. Morino, E. Yashima, Macro-
molecules 2007, 40, 6783–6785; (c) D. Zhang, C. Ren, W. Yang,
J. Deng, Macromol. Rapid Commun. 2012, 33, 652–657. For
leading references of other helical polymer-based asymmetric
catalysts, see: (d) E. Yashima, Y. Maeda, Y. Okamoto, Polym. J.
1999, 31, 1033–1036; (e) M. Reggelin, M. Schultz, M. Holbach,
Angew. Chem., Int. Ed. 2002, 41, 1614–1617; (f) M. Reggelin, S.
Doerr, M. Klussmann, M. Schultz, M. Holbach, Proc. Natl.
€
Acad. Sci. USA 2004, 101, 5461–5466; (g) C. A. Muller, T. Hof-
fart, M. Holbach, M. Reggelin, Macromolecules 2005, 38, 5375–
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Chirality 2009, 21, 44–50; (i) T. Yamamoto, M. Suginome,
Angew. Chem. Int. Ed. 2009, 48, 539–542; (j) K. Terada, T.
Masuda, F. Sanda, J. Polym. Sci. Part A: Polym. Chem. 2009,
47, 4971–4981; (k) T. Yamamoto, T. Yamada, Y. Nagata, M.
Suginome, J. Am. Chem. Soc. 2010, 132, 7899–7901; (l) A.
Ikeda, K. Terada, M. Shiotsuki, F. Sanda, J. Polym. Sci. Part A:
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M. Suginome, J. Am. Chem. Soc. 2012, 134, 11092–11095.
ACKNOWLEDGMENTS
This study was supported in part by a Grant-in-Aid for Scientific
Research (S) (E. Yashima) and Grant-in-Aid for Young Scientists
(B) (H. Iida) from the Japan Society for the Promotion of Science
(JSPS), and the Global COE Program “Elucidation and Design of
Materials and Molecular Functions” of the Ministry of Educa-
tion, Culture, Sports, Science, and Technology, Japan.
€
7 (a) H. Brunner, J. Bugler, B. Nuber, Tetrahedron: Asymmetry
1995, 6, 1699–1702; (b) C. G. Oliva, A. M. S. Silva, D. I. S. P.
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8 The absolute configurations at the 9-position of the sulfona-
mide-linked cinchona alkaloid monomers were opposite to
those of the native cinchona alkaloids, which were identical to
those of the amide-linked cinchona alkaloid monomers. See
ref. 4(b).
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