Asymmetric anionic polymerizations of 7-cyano-7-alkoxycarbonyl-1,4- benzoquinone methides

Article abstract of DOI:10.1002/pola.25054

Asymmetric anionic polymerizations of 7-cyano-7-alkoxycarbonyl-1,4- benzoquinone methides (1) with various alkoxy groups were performed using chiral initiators such as lithium isopropylphenoxide (ⁱPrPhOLi)/(S)-(-)-2, 2′-isopropylidene-bis(4-phe

Full text of DOI:10.1002/pola.25054

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
Asymmetric Anionic Polymerizations of
7-Cyano-7-Alkoxycarbonyl-1,4-Benzoquinone Methides
Takeshi Nagai,1 Takahiro Uno,1 Masataka Kubo,2 Takahito Itoh1
1Division of Chemistry for Materials, Graduate School of Engineering, Mie University, 1577 Kurima Machiya-cho, Tsu,
Mie 514-8507, Japan
2Graduate School of Regional Innovation Studies, Mie University, 1577 Kurima Machiya-cho, Tsu, Mie 514-8507, Japan
Correspondence to: T. Itoh (E-mail: itoh@chem.mie-u.ac.jp)
Received 17 June 2011; accepted 8 October 2011; published online 7 November 2011
DOI: 10.1002/pola.25054
ABSTRACT: Asymmetric anionic polymerizations of 7-cyano-7-
alkoxycarbonyl-1,4-benzoquinone methides (1) with various
alkoxy groups were performed using chiral initiators such as
lithium isopropylphenoxide (iPrPhOLi)/(S)-(–)-2,20-isopropyli-
dene-bis(4-phenyl-2-oxazoline) ((–)-PhBox) and lithium isopro-
pylphenoxide (iPrPhOLi)/(–)-sparteine ((–)-Sp) to investigate the
effect of the alkoxy groups of alkoxycarbonyl substituent in the
monomers 1 and chiral ligands of chiral initiators on the con-
trol of chiral center in the formation of polymers. Molar optical
rotation values of the polymers were significantly dependent
upon alkoxy groups, and the polymers with higher molar opti-
cal rotation were obtained in monomers with primary alkoxy
groups. The asymmetric anionic oligomerizations of the qui-
none methides having methoxy(1a), ethoxy(1b), and n-pro-
poxy(1c) groups with chiral initiators were carried out. Both 1-
mers and 2-mers were isolated and their optical resolutions
were performed to determine the extent of stereocontrol. High
stereoselectivity was observed at the propagation reaction, but
not at the initiation reaction. The effect of the counterion on
the control of chiral center in the formation of the polymer was
investigated in the asymmetric anionic polymerizations of 1b
i
i
with PrPhOM(M ¼ Li, Na, K)/(–)-Sp and PrPhOM(M ¼ Li, Na,
C
V
K)/(–)-PhBox initiators and discussed. 2011 Wiley Periodicals,
Inc. J Polym Sci Part A: Polym Chem 50: 466–479, 2012
KEYWORDS: anionic polymerization; chiral; initiators; synthesis
INTRODUCTION Asymmetric polymerization, classified in
asymmetric synthesis polymerization (IUPAC nomenclature:
asymmetric chirogenic polymerization), helix-sense-selective
polymerization, and enantiomer-selective polymerization, is
one of promising methods to introduce the chirality into the
polymer chain and to synthesize optically active polymers.
There are a large number of reports about the asymmetric
polymerizations based on vinyl monomers, diene monomers,
cyclic olefin monomers, aldehyde monomers, isocyanate
monomers and so on.1 Optically active polymers are applied
to chiral stationary phases for high performance liquid chro-
matography, polymeric reagents, and catalysts because of
their excellent chiral recognition abilities toward a wide
range of racemic compounds.2
(–)-PhBox) yielded an optically active polymer with a large
positive specific rotation ([a]435 ¼ þ90.4ꢀ).4 Moreover, to
understand the stereocontrol process in asymmetric poly-
merization of 1b, we carried out the asymmetric anionic oli-
gomerization of 1b and investigated the stereostructures of
oligomers such as 1-mer and 2-mer formed in the early
stage of the polymerization. It was found that the extent of
stereoselectivity in the formation of 1-mer as the initiation
step is quite low, but the formation of 2-mer corresponding
to the propagation step proceeds stereoselectively in the dia-
stereomeric excess (de) of 36%.4 However, the value of 36%
de for stereocontrol of polymer main chain was still not so
high. Here, investigation of substituent effect on the stereo-
control by asymmetric anionic polymerizations of 7-cyano-7-
alkoxycarbonyl-1,4-benzoquinone methides with various
alkoxy groups other than the ethoxy group is expected to
provide a clue to achieve the greater extent of stereocontrol
of chiral center for the polymer derived from a prochiral
monomer.
We recently reported the asymmetric anionic polymerization
of a prochiral monomer, 7-cyano-7-ethoxycarbonyl-1,4-benzo-
quinone methide (1b), using various chiral anionic initiators,
and the synthesis of an optically active polymer (poly(1b)) hav-
ing configurational chirality in the main chain (Scheme 1).3,4
In this work, the asymmetric anionic polymerizations of 7-
cyano-7-alkoxycarbonyl-1,4-benzoquinone methides bearing
various alkoxy groups such as methoxy(1a), ethoxy(1b),
The asymmetric anionic polymerization of 1b with a com-
plex of lithium 4-isopropylphenoxide and (–)-2,20-isopropyli-
denebis(4-phenyl-2-oxazoline) as the chiral ligand (iPrPhOLi/
C
V
2011 Wiley Periodicals, Inc.
466
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
in 150 mL of toluene using Dean-Stark water separator to
isolate water formed for 48 h. The reaction mixture was
washed twice with 100 mL of water and dried over anhy-
drous magnesium sulfate. It was placed under reduced pres-
sure to remove toluene to give a pale yellow solid, to which
was added 200 mL of a 2% aqueous sulfuric acid solution,
and refluxed for 1 h. After cooling, the reaction mixture was
extracted with chloroform (400 mL ꢁ 3). The combined or-
ganic fractions were washed twice with 100 mL of water,
dried over anhydrous magnesium sulfate, filtered, and the
solvent of the filtrate was evaporated under reduced pres-
sure. The crude product was purified by silica-gel column
chromatography using chloroform as eluent followed by
recrystallization from a mixture solution of hexane and
dichloromethane.
SCHEME 1 Preparation of optically active polymer by polymer-
ization of prochiral monomer 1b.
n-propoxy(1c), isopropoxy(1d), butoxy(1e), isobutoxy(1f),
sec-butoxy(1g), tert-butoxy(1h), benzyloxy(1i), and benzhy-
dryloxy(1j) using chiral initiators will be reported.
EXPERIMENTAL
Measurements
Melting points were measured with a Yanaco MP-S3 micro
melting point apparatus. Infrared (IR) spectra were recorded
on a JASCO IR-700 spectrometer. 1H and 13C NMR spectra
were measured with a JEOL JNM-EX270 (270 MHz for 1H)
spectrometer in chloroform-d with tetramethylsilane as an
internal standard. The specific optical rotation at 435 nm
([a]435) was obtained with a JASCO P-1030 polarimeter. The
molar optical rotations of polymers ([/]435) were calculated
from the specific optical rotation of polymers and the molec-
ular weights of those monomer unit (M) according to the fol-
4-[10-Cyano-10-(methoxycarbonyl)methylene]
cyclohexanone (2a)
From methyl cyanoacetate, 2a was obtained as pale yellow
needles (58.4% yield): mp: 67.0–69.0 C; IR (KBr, cmꢂ1): mCH
ꢀ
2970, mCN 2224, mC¼¼O 1728, mC¼¼C 1599, mCAO 1254, 1109.
1H NMR (CDCl3, ppm): d 3.86 (s, 3H), 3.41 (t, J ¼ 6.93 Hz,
2H), 3.14 (t, J ¼ 6.93 Hz, 2H), 2.58 (t, J ¼ 6.93 Hz, 2H), 2.55
(t, J ¼ 6.60 Hz, 2H). 13C NMR (CDCl3, ppm): d 208.3 (C¼¼O),
175.0 (C¼¼O), 161.6 (>C¼¼), 114.6 (CN), 104.2 (>C¼¼), 52.6
(CH3), 36.8 (CH2), 36.7 (CH2), 31.8 (CH2), 27.9 (CH2). Anal.
Calcd for C10H11NO3: C, 62.16%; H, 5.74%; N, 7.25%. Found:
C, 61.85%; H, 5.73%; N, 7.32%.
lowing equation: [/]435
¼
M[a]435/100. The molecular
weights of polymers were determined by gel permeation
chromatography (GPC) on a JASCO PU-1580 chromatograph
equipped with a JASCO RI-930 refractive index detector and
two TOSOH TSKgel MultiporeHXL-M columns using tetrahy-
drofuran (THF) as an eluent at a flow rate of 1.0 mL/min
and polystyrene standards for calibration at room tempera-
ture. Optical resolution of oligomers were performed on a
JASCO PU-1580 chromatograph equipped with a UV (JASCO
MD-910) and circular dichroism (JASCO CD-1595) detector
using chiral column, Daicel Chiralpak AD, at room tempera-
ture. A mixture solution of hexane/ethanol (90/10 in vol %)
was used as an eluent at a flow rate of 0.5 mL/min.
4-[10-Cyano-10-(ethoxycarbonyl)methylene]
cyclohexanone (2b)
From ethyl cyanoacetate, 2b was obtained as white needles
(74.0% yield): mp: 80-80.5 C; IR (KBr, cmꢂ1): mCH 2996, mCN
ꢀ
2226, mC¼¼O 1725, mC¼¼C 1596, mCAO 1253, 1105.
1H NMR (CDCl3, ppm): d 4.31 (q, J ¼ 7.30 Hz, 2H), 3.41 (t, J
¼ 6.90 Hz, 2H), 3.13 (t, J ¼ 6.60 Hz, 2H), 2.57 (t, J ¼ 6.90
Hz, 2H), 2.55 (t, J ¼ 6.60 Hz, 2H), 1.37 (t, J ¼ 7.30 Hz, 3H).
13C NMR (CDCl3, ppm): d 208.2 (C¼¼O), 174.2 (C¼¼O), 161.3
(>C¼¼), 114.7 (CN), 104.9 (>C¼¼), 62.1 (CH2), 37.0 (CH2),
36.9 (CH2), 31.9 (CH2), 28.0 (CH2), 14.0 (CH3). Anal. Calcd
Materials
Toluene was purified in the usual manner and distilled over
sodium metal. THF and dichloromethane were distilled over
sodium metal and calcium hydride, respectively. 4-Isopropyl-
phenol (Tokyo Kasei Kogyo) was recrystallized from hexane.
(–)-Sparteine ((–)-Sp) (Tokyo Kasei Kogyo) was dried over
calcium hydride and distilled under reduced pressure. (S)-(–)
-2,20-Isopropylidenebis(4-phenyl-2-oxazoline)
(Aldrich) was used without further purification.
((–)-PhBox)
Monomer Synthesis
4-[(Alkoxycarbonyl)cyanomethylene]cyclohexanones
(2a-j)
and 7-alkoxycarbonyl-7-cyano-1,4-benzoquinone methides
(1a-j) were synthesized by the same procedure reported
previously (Scheme 2).5,6
4-[(Alkoxycarbonyl)cyanomethylene]cyclohexanones (2a-j)
1,4-Cyclohexanedione monoethylene ketal (10 g, 64 mmol)
and alkyl cyanoacetate (70 mmol) were refluxed in the pres-
ence of 0.4 g of ammonium acetate and 2 mL of acetic acid
SCHEME 2 Preparation route of 7-alkoxycarbonyl-7-cyano-1,4-
benzoquinone methides.
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479
467

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
for C11H13NO3: C, 63.75%; H, 6.32%; N, 6.76%. Found: C,
63.90%; H, 6.58%; N, 6.67%.
4-[10-Cyano-10-(sec-butoxycarbonyl)
methylene]cyclohexanone (2g)
From sec-butyl cyanoacetate, 2g was obtained as a yellow oil
(82.0% yield): IR (neat, cmꢂ1): mCH 2978, mCN 2224, mC¼O
1723, mC¼¼C 1602, mCAO 1288, 1098.
4-[10-Cyano-10-(propoxycarbonyl)methylene]
cyclohexanone (2c)
From propyl cyanoacetate, 2c was obtained as white needles
(31.7% yield): mp: 87.5-88.0 ꢀC; IR (KBr, cmꢂ1): mCH 2976,
mCN 2220, mC¼O 1722, mC¼C 1594, mCAO 1285, 1116.
1H NMR (CDCl3, ppm): d 4.20 (t, J ¼ 6.60 Hz, 2H), 3.41 (t,
J ¼ 6.93 Hz, 2H), 3.13 (t, J ¼ 6.77 Hz, 2H), 2.57 (t, J ¼ 6.93
Hz, 2H), 2.55 (t, J ¼ 6.77 Hz 2H), 1.82-1.69 (m, 2H), 1.10 (t,
J ¼ 7.42 Hz, 3H). 13C NMR (CDCl3, ppm): d 208.2 (C¼¼O),
174.2 (C¼¼O), 161.3 (>C¼¼), 114.6 (CN), 104.7 (>C¼¼), 67.4
(CH2), 36.9 (CH2), 36.8 (CH2), 31.8 (CH2), 27.9 (CH2), 21.7
(CH2), 10.2 (CH3). Anal. Calcd for C12H15NO3: C, 65.14%; H,
6.83%; N, 6.33%. Found: C, 64.98%; H, 6.89%; N, 6.35%.
1H NMR (CDCl3, ppm): d 4.99 (m, 1H), 3.41 (t, J ¼ 6.93 Hz,
2H), 3.13 (t, J ¼ 6.93 Hz, 2H), 2.53-2.60 (m, 4H), 1.77-1.58
(m, 2H), 1.31 (d, J ¼ 6.27 Hz, 3H), 0.96 (t, J ¼ 7.43 Hz, 3H).
13C NMR (CDCl3, ppm): d 208.3 (C¼¼O), 173.7 (C¼¼O), 160.9
(>C¼¼), 114.7 (CN), 105.2 (>C¼¼), 74.5 (CH), 37.0 (CH2),
36.9 (CH2), 31.8 (CH2), 28.5 (CH2), 27.9 (CH2), 19.2 (CH3),
9.44 (CH3). Anal. Calcd for C13H17NO3: C, 66.36%; H, 7.29%;
N, 5.95%. Found: C, 66.39%; H, 7.35%; N, 5.92%.
4-[10-Cyano-10-(tert-butoxycarbonyl)
methylene]cyclohexanone (2h)
From tert-butyl cyanoacetate, 2h was obtained as a white
4-[10-Cyano-10-(isopropoxycarbonel)methylene]
cyclohexanone (2d)
From isopropyl cyanoacetate, 2d was obtained as white nee-
dles (64.8% yield): mp: 52.0-54.0 ꢀC; IR (KBr cmꢂ1): mCH
2984, mCN 2220, mC¼¼O 1721, mC¼¼C 1597, mCAO 1286, 1099.
1H NMR (CDCl3, ppm): d 5.19-5.08 (m, 1H), 3.40 (t, J ¼ 6.76
Hz, 2H), 3.12 (t, J ¼ 6.60 Hz, 2H), 2.57 (t, J ¼ 6.76 Hz, 2H),
2.55 (t, J ¼ 6.60 Hz, 2H), 1.34 (d, J ¼ 5.94 Hz, 6H). 13C NMR
(CDCl3, ppm): d 208.3 (C¼¼O), 173.7 (C¼¼O), 160.8 (>C¼¼),
114.7 (CN), 105.2 (>C¼¼), 70.0 (CH), 37.0 (CH2), 36.9 (CH2),
31.8 (CH2), 27.9 (CH2), 21.5 (CH3). Anal. Calcd for
needles (50.2% yield): mp: 94.0-95.0 C; IR (KBr, cmꢂ1): mCH
ꢀ
2978, mCN 2218, mC¼¼O 1715, mC¼¼C 1604, mCAO 1260, 1160.
1H NMR (CDCl3, ppm): d 3.37 (t, J ¼ 7.26 Hz, 2H), 3.10 (t, J ¼
7.26 Hz, 2H), 2.58-2.58 (m, 4H), 1.54 (s, 9H). 13C NMR (CDCl3,
ppm): d 208.4 (C¼¼O), 172.5 (C¼¼O), 160.4 (>C¼¼), 115.0
(CN), 106.3 (>C¼¼), 83.6 (>C<), 37.1 (CH2), 37.1 (CH2), 31.8
(CH2), 27.9 (CH2), 27.7 (CH3). Anal. Calcd for C13H17NO3: C,
66.36%; H, 7.29%; N, 5.95%. Found: C, 66.39%; H, 7.35%; N,
5.92%.
4-[10-Cyano-10-(benzyloxycarbonyl)
C12H15NO3: C, 65.14%; H, 6.83%; N, 6.33%. Found: C,
methylene]cyclohexanone (2i)
65.14%; H, 6.91%; N, 6.32%.
From benzyl cyanoacetate, 2i was obtained as a white nee-
dles (14.4% yield): mp: 115-117 ꢀC; IR (KBr, cmꢂ1): mCH
2866, mCN 2198, mC¼¼O 1691, mC¼¼C 1569, mCAO 1242, 1196.
4-[10-Cyano-10-(butoxycarbonyl)
methylene]cyclohexanone (2e)
1H NMR (CDCl3, ppm): d 7.41 (s, 5H), 5.29 (s, 2H), 3.40 (t, J ¼
13.9 Hz, 2H), 3.13 (t, J ¼ 13.5 Hz, 2H), 2.54 (m, 4H). 13C NMR
(CDCl3, ppm): d 208.2 (C¼¼O), 175.2 (C¼¼O), 161.1 (>C¼¼),
134.9 (Ar, CH), 128.7 (Ar, CH), 128.6 (Ar, CH), 128.1 (Ar, CH),
114.6 (CN), 104.6 (>C¼¼), 67.4 (CH2), 36.9 (CH2), 36.8 (CH2),
32.0 (CH2), 28.1 (CH2). Anal. Calcd for C16H15NO3: C, 71.35%;
H, 5.63%; N, 5.20%. Found: C, 71.39%; H, 5.56%; N, 5.21%.
From butyl cyanoacetate, 2e was obtained as white needles
(85% yield): mp: 65-66 ꢀC; IR (KBr, cmꢂ1): mCN 2202, mC¼O
1687, mC¼¼C 1565, mCAO 1233, 1085.
1H NMR (CDCl3, ppm): d 4.24 (t, J ¼ 6.6 Hz, 2H), 3.41 (t, J ¼
6.6 Hz, 2H), 3.13 (t, J ¼ 6.6 Hz, 2H), 2.55 (t, J ¼ 6.6 Hz, 4H),
1.69 (q, J ¼ 6.6 Hz, 2H), 1.44 (q, J ¼ 7.3 Hz, 2H), 0.96 (t, J ¼
7.3 Hz, 3H). 13C NMR (CDCl3, ppm): d 208.2 (C¼¼O), 174.1
(C¼¼O), 161.3 (>C¼¼), 114.6 (CN), 104.8 (>C¼¼), 65.8 (CH2),
36.95 (CH2), 36.86 (CH2), 31.8 (CH2), 30.3 (CH2), 27.9 (CH2),
18.9 (CH2), 13.5 (CH3). Anal. Calcd. for C13H17NO3: C, 66.36%;
H, 7.29%; N, 5.95%. Found: C, 66.21%; H, 7.37%; N, 5.99%.
4-[10-Cyano-10-(benzhydryloxycarbonyl)
methylene]cyclohexanone (2j)
From benzhydryl cyanoacetate, 2h was obtained as a pale yel-
low needles (51.1% yield): mp: 97.0-98.0 C; IR (KBr, cmꢂ1):
ꢀ
mCH 3038, mCN 2298, mC¼O 1724, mC¼C 1592, mCAO 1243, 1103.
4-[10-Cyano-10-(isobutoxycarbonyl)methylene]
cyclohexanone (2f)
From isobutyl cyanoacetate, 2f was obtained as a white nee-
dles (82.3% yield): mp: 53.0-54.0 ꢀC; IR (KBr, cmꢂ1): mCH
2966, mCN 2222, mC¼¼O 1724, mC¼¼C 1595, mCAO 1246, 1106.
1H NMR (CDCl3, ppm): d 4.02 (d, J ¼ 6.59 Hz, 2H), 3.41 (t, J
¼ 6.93 Hz, 2H), 3.14 (t, J ¼ 6.93 Hz, 2H), 2.58 (t, J ¼ 6.93
Hz, 2H), 2.55 (t, J ¼ 6.93 Hz, 2H), 2.02-1.99 (m, 1H), 1.05 (d,
J ¼ 6.92 Hz, 6H). 13C NMR (CDCl3, ppm): d 208.5 (C¼¼O),
174.5 (C¼¼O), 161.6 (>C¼¼), 115.0 (CN), 105.2 (>C¼¼), 72.2
(CH2), 37.3 (CH2), 37.3 (CH2), 32.2 (CH), 28.3 (CH2), 27.9
(CH2), 19.2 (CH3). Anal. Calcd for C13H17NO3: C, 66.36%; H,
7.28%; N, 5.95%. Found: C, 66.31%; H, 7.03%; N, 6.12%.
1H NMR (CDCl3, ppm): d 7.27-7.45 (m, 10H), 6.93 (s, 1H),
3.37 (t, J ¼ 6.93 Hz, 2H), 3.13 (t, J ¼ 6.60 Hz, 2H), 2.46-
2.55(m, 4H). 13C NMR (CDCl3, ppm): d 208.2 (C¼¼O), 175.2
(C¼¼O), 161.1 (>C¼¼), 134.9 (Ar, CH), 128.7 (Ar, CH), 128.6
(Ar, CH), 128.1 (Ar, CH), 114.6 (CN), 104.6 (>C¼¼), 67.4 (CH),
36.9 (CH2), 36.8 (CH2), 32.0 (CH2), 28.1 (CH2). Anal. Calcd
for C22H19NO3: C, 76.50%; H, 5.54%; N, 4.06%. Found: C,
76.57%; H, 5.55%; N, 4.05%.
7-Alkoxycarbonyl-7-cyano-1,4-benzoquinone
methides (1a-j)
About 2 g of compounds 2a-j was dissolved in 800 mL of
chloroform, and then into the resulting solution were added
468
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
10 g of activated manganese dioxide and 10 g of 4Å molecu-
lar sieves. The mixture was refluxed with stirring for 15-40
min, cooled, and then filtered. The orange filtrate was placed
under reduced pressure to remove chloroform to give an or-
ange solid residue, which was dissolved in a small amount of
chloroform. The resulting solution was passed through a
silica-gel column using chloroform as an eluent. The orange
elution band was collected and placed under reduced pres-
sure to remove solvent to obtain an orange solid, which was
recrystallized from hexane or a mixture solution of hexane
and dichloromethane to give orange needles.
Hz, 1H), 6.53 (dd, J ¼ 1.98, 10.23 Hz, 1H), 5.17-5.26 (m, 1H),
1.40 (d, J ¼ 6.27 Hz, 6H). 13C NMR (CDCl3, ppm): d 186.1
(C¼¼O), 159.9 (C¼¼O), 148.1 (>C¼¼), 136.2 (CH), 133.3 (CH),
132.8 (CH), 132.3 (CH), 114.4 (CN), 112.0 (¼¼C<), 71.9 (CH),
21.5 (CH3). Anal. Calcd for C12H11NO3: C, 66.35%; H, 5.10%;
N, 6.45%. Found: C, 66.35%; H, 5.01%; N, 6.47%.
7-Cyano-7-(butoxycarbonyl)-1,4-benzoquinone
methide (1e)
Yield: 22.3%; mp: 61.0-62.0 ꢀC; IR (KBr): mCH 2958, mCN
2318, mC¼¼O 1716, mC¼¼C 1642, mCAO 1265, 1082.
1H NMR (CDCl3, ppm): d 8.58 (dd, J ¼ 2.47, 10.39 Hz, 1H),
7.72 (dd, J ¼ 1.98, 10.22 Hz, 1H), 6.62 (dd, J ¼ 2.64, 10.22
Hz, 1H), 6.53 (dd, J ¼ 1.82, 10.44 Hz, 1H), 4.35 (t, J ¼ 6.60
Hz, 2H), 1.82-1.71 (m, 2H), 1.54-1.41 (m, 2H), 0.98 (t, J ¼
7.42 Hz, 3H). 13C NMR (CDCl3, ppm): d 186.0 (C¼¼O), 160.5
(C¼¼O), 148.4 (>C¼¼), 136.2 (CH), 133.4 (CH), 132.8 (CH),
132.3 (CH), 114.4 (CN), 111.4 (¼¼C<), 67.1 (CH2), 30.2 (CH2),
18.9 (CH2), 13.5 (CH3). Anal. Calcd for C13H13NO3: C, 67.52%;
H, 5.67%; N, 6.06%. Found: C, 67.40%; H, 5.61%; N, 6.10%.
7-Cyano-7-(methoxycarbonyl)-1,4-benzoquinone
methide (1a)
Yield: 23%; mp: 104-105 ꢀC; IR (KBr, cmꢂ1): mCH 2960, mCN
2216, mC¼¼O 1726, mC¼¼C 1639, mCAO 1240, 1081.
1H NMR (CDCl3, ppm): d 8.58 (dd, J ¼ 2.64, 10.56 Hz, 1H),
7.72 (dd, J ¼ 1.98, 10.22 Hz, 1H), 6.62 (dd, J ¼ 2.48, 10.07
Hz, 1H), 6.54 (dd, J ¼ 1.98, 10.23 Hz, 1H), 3.97 (s, 3H). 13C
NMR (CDCl3, ppm): d 186.0 (C¼¼O), 160.9 (C¼¼O), 148.8
(>C¼¼), 136.1 (CH), 133.5 (CH), 132.7 (CH), 132.4 (CH),
114.4 (CN), 110.8 (¼¼C<), 53.8 (CH3). Anal. Calcd for
7-Cyano-7-(isobutoxycarbonyl)-1,4-benzoquinone
methide (1f)
Yield: 18.0%; mp: 74.0-75.0 ꢀC; IR (KBr): mCH 2968, mCN
2216, mC¼¼O 1714, mC¼¼C 1642, mCAO 1263, 1082.
C10H7NO3: C, 63.49%; H, 3.73%; N, 7.40%. Found: C,
62.38%; H, 3.56%; N, 7.73%.
7-Cyano-7-(ethoxycarbonyl)-1,4-benzoquinone
methide (1b)
1H NMR (CDCl3, ppm): d 8.56 (dd, J ¼ 2.64, 10.23 Hz, 1H),
7.72 (dd, J ¼ 1.82, 10.06 Hz, 1H), 6.62 (dd, J ¼ 2.64, 9.90
Hz, 1H), 6.54 (dd, J ¼ 1.98, 10.23 Hz, 1H), 4.13 (d, J ¼ 6.60
Hz, 2H), 2.04-2.14 (m, 1H), 1.03 (d, J ¼ 6.60 Hz, 3H). 13C
NMR (CDCl3, ppm): d 186.1 (C¼¼O), 160.4 (C¼¼O), 148.4
(>C¼¼), 136.2 (CH), 133.4 (CH), 132.8 (CH), 132.4 (CH),
114.4 (CN), 111.4 (¼¼C<), 73.1 (CH2), 27.6 (CH), 18.9 (CH3).
Anal. Calcd for C13H13NO3: C, 67.52%; H, 5.67%; N, 6.06%.
Found: C, 67.40%; H, 5.61%; N, 6.10%.
Yield: 41.2%; mp. 56.5-57.5 ꢀC; IR (KBr, cmꢂ1): mCH 2982,
mCN 2218, mC¼O 1738, mC¼C 1642, mCAO 1236, 1083.
1H NMR (CDCl3, ppm): d 8.57 (dd, J ¼ 2.64, 10.23 Hz, 1H),
7.72 (dd, J ¼ 1.98, 9.98 Hz, 1H), 6.62 (dd, J ¼ 2.64, 9.90 Hz,
1H), 6.54 (dd, J ¼ 1.98, 10.23 Hz, 1H), 4.43 (q, J ¼ 6.93 Hz,
2H), 1.42 (t, J ¼ 6.93 Hz, 3H). 13C NMR (CDCl3, ppm): d
186.1 (C¼¼O), 160.5 (C¼¼O), 148.5 (>C¼¼), 136.2 (CH), 133.5
(CH), 132.8 (CH), 132.4 (CH), 114.5 (CN), 111.5 (¼¼C<), 63.5
(CH2), 14.0 (CH3). Anal. Calcd for C11H9NO3: C, 65.02%; H,
4.46%; N, 6.89%. Found: C, 64.81%; H, 4.43%; N, 6.95%.
7-Cyano-7-(sec-butoxycarbonyl)-1,4-benzoquinone
methide (1g)
Yield: 12.0%; mp: 57.5-58 ꢀC; IR (KBr, cmꢂ1): mCH 2980, mCN
2216, mC¼¼O 1717, mC¼¼C 1643, mCAO 1233, 1097.
7-Cyano-7-(propoxycarbonyl)-1,4-benzoquinone
methide (1c)
1H NMR (CDCl3, ppm): d 8.57 (dd, J ¼ 2.64, 10.23 Hz, 1H),
7.72 (dd, J ¼ 1.98, 9.89 Hz, 1H), 6.61 (dd, J ¼ 2.64, 10.23
Hz, 1H), 6.53 (dd, J ¼ 1.98, 10.23 Hz, 1H), 5.04-5.09 (m, 1H),
1.67-1.80 (m, 2H), 1.37 (d, J ¼ 6.27 Hz, 3H), 0.99 (t, J ¼ 7.43
Hz, 3H). 13C NMR (CDCl3, ppm): d 186.1 (C¼¼O), 160.1
(C¼¼O), 148.2 (>C¼¼), 136.2 (CH), 133.3 (CH), 132.9 (CH),
132.3 (CH), 114.4 (CN), 112.1 (¼¼C<), 76.4 (CH), 28.5 (CH2),
19.2 (CH3), 9.5 (CH3). Anal. Calcd for C13H13NO3: C, 67.52%;
H, 5.67%; N, 6.06%. Found: C, 67.37%; H, 5.65%; N, 6.09%.
Yield: 15.2%; mp: 68-69.5 ꢀC; IR (KBr, cmꢂ1): mCH 2970, mCN
2216, mC¼¼O 1716, mC¼¼C 1642, mCAO 1266, 1083.
1H NMR (CDCl3, ppm): d 8.58 (dd, J ¼ 2.47. 10.39 Hz, 1H),
7.72 (dd, J ¼ 1.82, 10.06 Hz, 1H), 6.62 (dd, J ¼ 2.64, 9.90
Hz, 1H), 6.54 (dd, J ¼ 1.82, 10.40 Hz, 1H), 4.31 (t, J ¼ 6.60
Hz, 2H), 1.87-1.74 (m, 2H), 1.04 (t, J ¼ 7.43 Hz, 3H). 13C
NMR (CDCl3, ppm): d 186.1 (C¼¼O), 160.5 (C¼¼O), 148.5
(>C¼¼), 136.2 (CH), 133.4 (CH), 132.8 (CH), 132.4 (CH),
114.5 (CN), 111.4 (¼¼C<), 68.8 (CH2), 21.7 (CH2), 10.2 (CH3).
Anal. Calcd for C12H11NO3: C, 66.35%; H, 5.10%; N, 6.45%.
Found: C, 65.54%; H, 4.97%; N, 6.37%.
7-Cyano-7-(tert-butoxycarbonyl)-1,4-benzoquinone
methide (1h)
Yield: 47.3%; mp: 120-121 C; IR (KBr, cmꢂ1): mCH 2992, mCN
ꢀ
7-Cyano-7-(isoproxycarbonyl)-1,4-benzoquinone
methide (1d)
2214, mC¼¼O 1722, mC¼¼C 1642, mCAO 1251, 1083.
1H NMR (CDCl3, ppm): d 8.54 (dd, J ¼ 2.64, 10.23 Hz, 1H),
7.69 (dd, J ¼ 1.98, 10.23 Hz, 1H), 6.59 (dd, J ¼ 2.64, 10.22
Hz, 1H), 6.51 (dd, J ¼ 1.98, 10.23 Hz, 1H), 1.60 (s, 9H). 13C
NMR (CDCl3, ppm): d 186.6 (C¼¼O), 159.8 (C¼¼O), 148.0
(>C¼¼), 136.8 (CH), 133.6 (CH), 133.3 (CH), 132.6 (CH),
Yield: 44.0%; mp: 91.0-92.0 ꢀC; IR (KBr, cmꢂ1): mCH 2990,
mCN 2218, mC¼O 1721, mC¼C 1643, mCAO 1250, 1100.
1H NMR (CDCl3, ppm): d 8.54 (dd, J ¼ 2.64, 10.23 Hz, 1H),
7.71 (dd, J ¼ 1.82, 10.06 Hz, 1H), 6.61 (dd, J ¼ 2.64, 10.23
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479
469

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
115.1 (CN), 113.8 (¼¼C<), 86.2 (>C<), 28.3 (CH3). Anal.
Calcd for C13H13NO3: C, 67.52%; H, 5.67%; N, 6.06%. Found:
C, 67.37%; H, 5.65%; N, 6.09%.
poured into 10 mL of chloroform, and the resulting solution
was washed with water, 1N hydrochloric acid, saturated so-
dium bicarbonate aqueous solution, and saturated sodium
chloride aqueous solution, and then dried over anhydrous
magnesium sulfate. The filtrate was concentrated, and passed
through a silica gel column by using hexane/diethyl ether
(2/1 v/v) as an eluent. The first elution band and the second
one were collected and placed under reduced pressure to
give 1-mer and 2-mer as white solids, respectively.
7-Cyano-7-(benzyloxycarbonyl)-1,4-benzoquinone
methide (1i)
Yield: 42.7%; mp: 145-146 C; IR (KBr, cmꢂ1): mCH 2920, mCN
ꢀ
2198, mC¼¼O 1694, mC¼¼C 1583, mCAO 1231, 1084.
1H NMR (CDCl3, ppm): d 8.54 (dd, J ¼ 2.64, 10.23 Hz, 1H),
7.72 (dd, J ¼ 1.98, 9.89 Hz, 1H), 7.43 (m, 5H), 6.62 (dd, J ¼
2.64, 10.23 Hz, 1H), 6.54 (dd, J ¼ 1.98, 9.89 Hz, 1H), 5.37 (s,
2H). 13C NMR (CDCl3, ppm): d 186.0 (C¼¼O), 160.3 (C¼¼O),
148.8 (>C¼¼), 136.1 (CH), 134.1 (Ar, CH), 133.4 (CH), 132.7
(Ar, CH), 128.8 (Ar, CH), 128.3 (Ar, CH), 114.3 (CN), 111.1
(¼¼C<), 68.7 (CH2). Anal. Calcd for C16H11NO3: C, 72.44%; H,
4.19%; N, 5.28%. Found: C, 72.37%; H, 4.21%; N, 5.22%.
1a: 1-mer: 28.9 mg (10.4% yield). IR (KBr, cmꢂ1): mCH 2962,
mCN 2312, mC¼O 1768, mCAO 1201, 1088. 1H NMR (CDCl3,
ppm): d 7.82 (d, J ¼ 6.90 Hz, 2H), 7.21-7.24 (m, 4H), 6.99
(d, J ¼ 6.58 Hz, 2H), 3.82 (s, 3H), 2.87 (sept, J ¼ 6.93 Hz,
1H), 2.32 (s, 3H), 1.22 (d, J ¼ 6.93 Hz, 6H). 13C NMR (CDCl3,
ppm): d 169.0 (C¼¼O), 165.3 (C¼¼O), 152.2 (Ar, quaternary),
152.1 (Ar, quaternary), 144.7 (Ar, quaternary), 130.8 (Ar,
CH), 127.7 (Ar, quatrenary), 127.5 (Ar, CH), 122.3 (Ar, CH),
118.0 (Ar, CH), 115.4 (CN), 79.0 (>C<, quatrenary), 54.4
(CH3), 33.4 (CH), 24.0 (CH3), 21.1 (CH3).
7-Cyano-7-(benzhydryloxycarbonyl)-1,4-benzoquinone
methide (1j)
Yield: 19.9%; mp: 125-126.5 ꢀC; IR (KBr, cmꢂ1): mCH 3042,
mCN 2218, mC¼O 1726, mC¼C 1639, mCAO 1235, 1081.
2-mer: 49.0 mg (17.6% yield). IR (NaCl, cmꢂ1):mCAO 2964,
1H NMR (CDCl3, ppm): d 8.57 (dd, J ¼ 2.31, 10.23 Hz, 1H),
7.75 (dd, J ¼ 1.98, 9.89 Hz, 1H), 7.32-7.46 (m, 10H), 7.01 (s,
1H), 6.61 (dd, J ¼ 2.64, 10.23 Hz, 1H), 6.50 (dd, J ¼ 1.98,
9.89 Hz, 1H). 13C NMR (CDCl3, ppm): d 186.1 (C¼¼O), 159.5
(C¼¼O), 149.2 (>C¼¼), 138.7 (Ar, CH), 136.1 (CH), 133.5 (CH),
132.7 (CH), 132.5 (CH), 128.8 (Ar, CH), 128.5 (Ar, CH), 126.9
(Ar, CH), 114.5 (CN), 111.1 (¼¼C<), 80.0 (CH). Anal. Calcd for
mCN 2254, mC¼O 1761, m
1215, 1092. 1H NMR (CDCl3,
CAO
ppm): d 7.81 (d, J ¼ 8.91 Hz, 2H), 7.76 (d, J ¼ 8.58 Hz, 2H),
7.26 (d, J ¼ 8.90 Hz, 2H), 7.19 (d, J ¼ 8.58 Hz, 2H), 7.15 (d,
J ¼ 8.91 Hz, 2H), 7.06 (d, J ¼ 8.91 Hz, 2H), 3.84 (s, 3H), 3.85
(s, 3H), 2.87 (sept, J ¼ 6.93 Hz, 1H), 2.33 (s, 3H), 1.22 (d, J
¼ 6.93 Hz, 6H). 13C NMR (CDCl3, ppm): d 169.3 (C¼¼O),
165.7 (C¼¼O), 164.9 (C¼¼O), 155.9 (Ar, quaternary), 152.7
(Ar, quaternary), 145.0 (Ar, quaternary), 130.2 (Ar, quater-
nary), 129.0 (Ar, quaternary), 128.2 (Ar, CH), 127.8 (Ar, CH),
122.9 (Ar, CH), 122.9 (Ar, CH), 118.4 (Ar, CH), 118.3 (Ar, CH),
116.7 (CN), 115.7 (CN), 79.2 (>C<, quaternary), 78.6 (>C<,
quaternary), 55.1 (CH3), 54.8 (CH3), 33.7 (CH), 24.3 (CH3),
21.4 (CH3).
C22H15NO3: C, 77.41%; H, 4.43%; N, 4.10%. Found: C,
77.04%; H, 4.32%; N, 4.30%.
Asymmetric Anionic Polymerization
Asymmetric anionic polymerization was carried out in a glass
ampoule equipped with a three-way stopcock. A given amount
of 1a-j was placed in the ampoule, dried under reduced pres-
sure, and then filled with nitrogen. Into it was added dry
dichloromethane or a mixture solution of dry dichlorome-
thane/toluene (30/70 in vol %) by a syringe, and the result-
ing solution was cooled to –78 ꢀC. The polymerization was
initiated by adding the initiator solution, which was prepared
by mixing lithium 4-isopropylphenoxide (iPrPhOLi) (1.0
equiv.) and a chiral ligand (1.1 equiv.) (–)-Sp or (–)-PhBox in
dry toluene at room temperature just before use, and the
reaction mixture was stirred at –78 ꢀC for a given time. The
polymerization was terminated by adding an excess amount
of dry acetic anhydride. The resulting solution was poured
into a large excess amount of hexane, and the deposited poly-
mer was collected by centrifugation, and dried in vacuo. Same
polymerization was carried out in a mixture solution of dry
dichloromethane/toluene (40/60 in vol %) at –40 ꢀC. The
rest procedure is similar to the aforementioned method.
1b: 1-mer: 15.8 mg (8.3% yield). IR (KBr, cmꢂ1): mCH 2970,
mCN 2310, mC¼O 1766, mCAO 1200. 1H NMR (CDCl3, ppm): d
7.82 (d, J ¼ 8.91 Hz, 2H), 7.21 (d, J ¼ 8.91 Hz, 2H), 7.16 (d,
J ¼ 8.58 Hz, 2H), 7.00 (d, J ¼ 8.58 Hz, 2H), 4.26 (q, J ¼ 7.26
Hz, 2H), 2.87 (sept, J ¼ 6.93 Hz, 1H), 2.32 (s, 3H), 1.22 (d,
J ¼ 6.93 Hz, 6H), 1.21 (t, J ¼ 7.26 Hz, 3H). 13C NMR (CDCl3,
ppm): d 168.9 (C¼¼O), 164.7 (C¼¼O), 152.3 (Ar, quaternary),
152.0 (Ar, quaternary), 144.5 (Ar, quaternary), 130.9 (Ar,
CH), 127.4 (Ar, quatrenary), 127.4 (Ar, CH), 122.2 (Ar, CH),
118.0 (Ar, CH), 115.5 (CN), 79.0 (>C<, quatrenary), 63.9
(CH2), 33.3 (CH), 23.9 (CH3), 21.0 (CH3), 13.6 (CH3).
2-mer: 34.3 mg (11.4% yield). IR (NaCl, cmꢂ1):mCAO 2970,
mCN 2324, mC¼O 1770, mCAO 1200. 1H NMR (CDCl3, ppm): d
7.81 (d, J ¼ 8.91 Hz, 2H), 7.76 (d, J ¼ 8.58 Hz, 2H), 7.23 (d,
J ¼ 8.90 Hz, 2H), 7.23 (d, J ¼ 8.58 Hz, 2H), 7.15 (d, J ¼ 8.91
Hz, 2H), 6.99 (d, J ¼ 8.91 Hz, 2H), 4.25 (q, J ¼ 7.26 Hz, 4H),
2.87 (sept, J ¼ 6.93 Hz, 1H), 2.33 (s, 3H), 1.29-1.17 (t, J ¼
7.26 Hz, 6H), 1.21 (d, J ¼ 6.60 Hz, 6H). 13C NMR (CDCl3,
ppm): d 168.9 (C¼¼O), 164.7 (C¼¼O), 164.0 (C¼¼O), 155.6 (Ar,
quaternary), 152.3 (Ar, quaternary), 144.5 (Ar, quaternary),
130.0 (Ar, quaternary), 128.8 (Ar, quaternary), 127.7 (Ar,
CH), 127.5 (Ar, CH), 127.4 (Ar, CH), 122.4 (Ar, CH), 122.3 (Ar,
CH), 117.9 (Ar, CH), 115.5 (CN), 115.0 (CN), 78.9 (>C<,
i
Oligomerization with PrPhOLi/(–)-PhBox Initiator
and Isolation of 1-mer and 2-mer
Asymmetric anionic oligomerization of 1a, 1b, or 1c with
iPrPhOLi/(–)-PhBox initiators was carried out at [monomer]/
[initiator] ratio of 2 in dichloromethane at –78 ꢀC for 12hr.
The oligomerization was terminated by adding an excess
amount of dry acetic anhydride. The reaction mixture was
470
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
TABLE 1 Asymmetric Anionic Polymerizations of 1a-d, 1h, and
quaternary), 78.8 (>C<, quaternary), 64.3 (CH2), 63.9 (CH2),
33.3 (CH), 24.0 (CH3), 21.1 (CH3), 13.7 (CH3).
i
1j with PrPhOLi/(–)-Sp Initiator in Dichloromethane/Toluene
(30/70 in vol %) at 278 8Ca
1c: 1-mer: 43.3 mg (14.1% yield). IR (KBr, cmꢂ1): mCH 2966,
mCN 2348, mC¼O 1765, mCAO 1200, 1088. 1H NMR (CDCl3,
ppm): d 7.83 (d, J ¼ 8.91 Hz, 2H), 7.24 (d, J ¼ 8.91 Hz, 2H),
7.21 (d, J ¼ 8.58 Hz, 2H), 7.02 (d, J ¼ 8.58 Hz, 2H), 4.11-
4.19 (m, 2H), 2.87 (sept, J ¼ 6.93 Hz, 1H), 2.32 (s, 3H), 1.54-
1.64 (m, 2H), 1.22 (d, J ¼ 6.93 Hz, 6H), 0.80 (t, J ¼ 7.43 Hz,
3H). 13C NMR (CDCl3, ppm): d 169.0 (C¼¼O), 164.8 (C¼¼O),
152.4 (Ar, quaternary), 152.1 (Ar, quaternary), 144.5 (Ar,
quaternary), 131.0 (Ar, CH), 127.4 (Ar, quatrenary), 127.4
(Ar, CH), 122.2 (Ar, CH), 117.8 (Ar, CH), 115.6 (CN), 79.0
(>C<, quatrenary), 63.4 (CH2), 33.4 (CH), 24.0 (CH3), 21.6
(CH2), 21.1 (CH2), 9.96 (CH3).
Alkoxy
Yield/%b
Mn (DP)c
[a]435
[/]435
d
d
Monomer
Group
1a
1b
1c
1d
1h
1j
Me
Et
nPr
iPr
tBu
81
70
63
52
58
65
2,000 (11)
1,900 (9)
1,900 (9)
1,800 (8)
3,500 (15)
2,100 (9)
ꢂ1.7ꢀ
ꢂ3.5ꢀ
ꢂ4.5ꢀ
ꢂ4.0ꢀ
ꢂ5.6ꢀ
ꢂ3.1ꢀ
ꢂ3.2ꢀ
ꢂ7.1ꢀ
ꢂ9.8ꢀ
ꢂ8.7ꢀ
ꢂ12.9
ꢂ10.6ꢀ
CHPh2
a
Conditions: [Monomer]
Time: 48 h.
¼
0.12 mol/L, [Monomer]/[Initiator]
¼
20,
2-mer: 67.5 mg (22.0% yield). IR (NaCl, cmꢂ1):mCAO 2970,
mCN 2350, mC¼O 1769, mCAO 1203, 1089. 1H NMR (CDCl3,
ppm): d 7.84-7.74 (m, 4H), 7.26-7.14 (m, 4H), 7.03-6.97 (m,
4H), 4.22-4.11 (m, 4H), 2.87 (sept, J ¼ 6.93 Hz, 1H), 2.33 (s,
3H), 1.66-1.55 (m, 4H), 1.21 (d, J ¼ 6.93 Hz, 6H), 0.90-0.76
(m, 6H). 13C NMR (CDCl3, ppm): d 168.9 (C¼¼O), 164.8
(C¼¼O), 164.1 (C¼¼O), 155.6 (Ar, quaternary), 152.3 (Ar, qua-
ternary), 152.2 (Ar, quaternary), 144.5 (Ar, quaternary),
130.1 (Ar, quaternary), 128.9 (Ar, quaternary), 127.7 (Ar,
CH), 127.4 (Ar, CH), 127.3 (Ar, CH), 122.4 (Ar, CH), 122.4 (Ar,
CH), 118.0 (Ar, CH), 115.5 (CN), 115.0 (CN), 78.9 (>C<, qua-
ternary), 78.4 (>C<, quaternary), 69.7 (CH2), 69.3 (CH2),
33.3 (CH), 24.0 (CH2), 21.6 (CH2), 21.0 (CH3), 9.90 (CH3).
b
Hexane-insoluble part.
Determined by GPC as polystyrene standard. Degree of polymerization
(DP) was determined by 1H NMR.
c
d
In chloroform.
parison with 1h, a polymer with a smaller molar optical
rotation value ([/]435 ¼ –10.6ꢀ) is formed, probably due to
the change of the system from homogeneous state to hetero-
geneous state in the progress of polymerization. Anyway, on
the basis of the molar optical rotation values, stereoselectiv-
ity in the asymmetric anionic polymerizations of 1a-d, 1h,
i
and 1j using the PrPhOLi/(–)-Sp initiator might be improved
with an increase in the bulkiness of the alkoxy groups of the
monomers. However, very low molar optical rotation values
of the resulting polymers indicate low stereocontrol in the
polymerization reaction.
RESULTS AND DISCUSSION
Asymmetric Anionic Polymerizations
We carried out the asymmetric anionic polymerizations of
Next, we investigated the asymmetric anionic polymeriza-
tions of 1a-j using the iPrPhOLi/(–)-PhBox initiator at
[monomer]/[iPrPhOLi/(–)-PhBox] ratio of 20. To keep a sys-
tem homogeneous state during the polymerizations at a
monomer concentration of 0.23 mol/L for all monomers, pol-
ymerizations were performed in two conditions, one is in
i
1a-d, 1h, and 1j with the PrPhOLi/(–)-Sp initiator at [mono-
mer]/[iPrPhOLi/(–)-Sp] ratio of 20 in a mixture solution of
ꢀ
dichloromethane/toluene (30/70 in vol %) at –78 C. To per-
form asymmetric anionic polymerization in the homogeneous
state for all of six monomers in a mixture solution of
dichloromethane/toluene (30/70 in vol %) at –78 ꢀC, the
polymerizations were carried out at a monomer concentra-
tion of 0.12 mol/L instead of 0.23 mol/L used in previous
work4 for the asymmetric anionic polymerization of 1b. Pol-
ymerizations proceeded homogenously for all monomers
except for 1j, but 1j became gradually heterogeneous, due to
low solubility of resulting polymer toward a mixture solution
of dichloromethane/toluene (30/70 in vol %). The results
are summarized in Table 1.
ꢀ
dichloromethane at –78 C for 1a-e, 1g and 1h, and another
is in a mixture solution of dichloromethane/toluene (40/60
in vol %) at –40 ꢀC for 1a-j. All polymerization reactions
proceeded homogenously. The results in dichloromethane at
–78 ꢀC for 1a-e, 1g and 1h, and in a mixture solution of
ꢀ
dichloromethane/toluene (40/60 in vol %) at –40 C for 1a-
j are summarized in Tables 2 and 3, respectively.
In the Table 2, asymmetric anionic polymerizations afforded
optically active polymers having the number-average molecu-
lar weights in the range 2000 to 3800, and the molecular
weight distributions in the range 1.3 to 1.4. In the polymer-
izations of 1a-d and 1h except for 1e and 1g, both polymer
yields and molecular weights have a tendency to decrease
with increasing the bulkiness of alkoxy groups in the mono-
mers. It seems that an attack of the propagating phenoxide
anion upon the exomethylene carbon of the monomers is
suppressed gradually with an increase in bulkiness of the
alkoxy groups. And also, the molar optical rotation values of
the polymers showed a tendency of decrease with increasing
the bulkiness of the alkoxy groups, and 1b provided an
Asymmetric anionic polymerizations afforded optically active
polymers in moderate yields, which have the number-aver-
age molecular weights in the range 1800 to 3500, and the
molecular weight distributions in the range 1.3 to 1.4. The
molar optical rotation values of the obtained polymers
depend upon the alkoxy groups of the monomers, where the
tendency of the values increases with an increase in the
bulkiness of the alkoxy groups. 1h with tert-butoxy group
provided an optically active polymer with a maximum nega-
tive molar optical rotation value ([/]435 ¼ –12.9ꢀ). Here,
although 1j has a more bulky benzhydryloxy group in com-
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479
471

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
TABLE 2 Asymmetric Anionic Polymerizations of 1a-e, 1g,
cally active polymer and the effect of the initiator systems
on the control of chiral center. Here, we carried out the
asymmetric anionic oligomerizations of 1a-c with the Pr-
i
and 1h with PrPhOLi/(–)-PhBox Initiator in Dichloromethane
at 278 8Ca
i
PhOLi/(–)-PhBox initiator in dichloromethane at –78 ꢀC to
investigate the effect of alkoxy groups on the control of chi-
ral center in the formation of an optically active polymer.
The results are summarized in Table 4, together with the
previous result of the oligomerization of 1b in a mixture so-
lution of dichloromethane/toluene (30/70 in vol %) at –78
ꢀC. In the oligomerization of 1b in a mixture solution, higher
oligomers such as 3-mer and 4-mer were scarcely produced
even in 24h. On the other hand, the higher oligomers were
slightly produced at the oligomerizations of 1a-c in
dichloromethane.
Alkoxy
Monomer Group Yield/%b Mn (DP)c
[a]435 (ꢀ) [/]435 (ꢀ)
d
d
1a
1b
1c
1d
1e
1g
1h
a
Me
Et
nPr
iPr
nBu
sBu
tBu
97
96
88
52
21
16
45
2,400 (16) þ22.1
2,700 (20) þ53.6
2,600 (17) þ42.0
2,000 (12) þ23.1
3,400 (15) þ45.2
þ41.8
þ108.9
þ91.2
þ50.2
þ104.5
ꢂ1.7
3,800 (16)
ꢂ0.74
þ1.0
2,100 (11)
þ2.3
Conditions: [Monomer] ¼ 0.23 mol/L, [Monomer]/[Initiator] ¼ 20, time:
The 1-mers and 2-mers obtained by oligomerizations (run 1
and 2) of 1a and 1b showed a positive specific optical rota-
tion similar to the corresponding polymers. On the other
hand, the products obtained by oligomerization (run 3) of 1c
had a very small negative specific optical rotation values for
the 1-mer and a large positive one for 2-mer, indicating that,
in the asymmetric anionic polymerization of 1c, stereoselec-
tivity in an initiation reaction is different from that in a
propagation reaction. Moreover, opposite sign in the specific
optical rotation between 1-mers (positive sign) of 1a,b and
1-mer (negative sign) of 1c suggests the different stereose-
lectivity at the initiation step, and also small values in 1-
mers for 1a-c mean very low control of chiral center. To
obtain further information on stereoselectivity in the 1-mer
and 2-mer, optical resolutions of them were conducted with
high pressure liquid chromatography (HPLC) analysis on the
chiral column using hexane/ethanol (90/10 in vol %) as an
eluent. The chromatograms of the optical resolution of the 1-
mer obtained by oligomerizations are shown in Figure 1(a)
48 h.
b
Hexane-insoluble part.
c
Determined by GPC as polystyrene standard. Degree of polymerization
(DP) is determined by 1H NMR.
d
In chloroform.
optically active polymer with the maximum positive molar
optical rotation value ([/]435 ¼ þ108.9ꢀ).
In the Table 3, all monomers afforded optically active poly-
mers in quantitative yields for 1a-h and in moderate yields
for 1i and 1j, which have the number-average molecular
weights in the range 2500 to 7000, and the molecular
weight distributions in the range 1.3 to 1.4. The lower yield
and the lower molecular weights for 1i and 1j in comparison
with for 1a-h are due to a lower concentration, arising from
a slight heterogeneous state of the systems observed even in
this condition. The 1b afforded an optically active polymer
with the maximum positive molar optical rotation value
([/]435 ¼ þ100.2ꢀ) as well as the case of the asymmetric an-
ionic polymerizations in dichloromethane ([/]435
¼
þ108.9ꢀ). This indicates that ethoxy group is a suitable sub-
stituent for the stereocontrol among the substituents investi-
gated in the asymmetric anionic polymerizations with a (–)-
PhBox ligand. The molar optical rotation of the optically
active polymers takes a maximum value at ethoxy group, and
decreases in a following order: primary alkoxy > secondary
alkoxy > tertiary alkoxy > aromatic ring. This indicates that
higher stereocontrol in the polymers was achieved at a
monomer with relatively small primary alkoxy group in con-
trast to the results of the polymerization with a (–)-Sp
ligand, where a maximum molar optical rotation value was
obtained for 1g having the bulky tert-butoxy group. It is
speculated that a specific conformation might be formed
between chiral ligand and alkoxy group of alkoxycarbonyl
substituents in the monomer 1, and then a certain specified
polymerization, where the size of the monomer could deter-
mine the stereoselectivity, might take place.
TABLE 3 Asymmetric Anionic Polymerizations of 1a-j with
iPrPhOLi/(–)-PhBox Initiator in Dichloromethane/Toluene
(40/60 in vol %) at 240 8Ca
Alkoxy
Monomer Group Yield/%b Mn (DP)c [a]435 (ꢀ)d [/]435 (ꢀ)d
1a
1b
1c
1d
1e
1f
Me
100
99
5,200 (27) þ44.3
5,200 (25) þ49.3
6,300 (28) þ42.2
6,300 (28) þ26.9
3,800 (16) þ27.9
7,000 (29) þ39.0
7,000 (29) þ13.8
þ83.8
þ100.2
þ91.7
þ58.4
þ64.5
þ90.2
þ31.9
þ19.7
þ13.0
ꢂ4.4
Et
nPr
iPr
nBu
iBu
sBu
tBu
97
100
100
99
1g
1h
1i
99
97
4,700 (20)
2,500 (9)
3,000 (20)
þ8.5
þ4.9
ꢂ1.3
CH2Ph
CHPh2
51
1j
59
a
Stereoselectivity in the Initiation and Propagation Steps
Conditions: [Monomer] ¼ 0.23 mol/L, [Monomer]/[Initiator] ¼ 20, time:
In previous paper,4 we carried out an asymmetric anionic
48 h.
b
i
i
Hexane-insoluble part.
oligomerization of 1b with the PrPhOLi/(–)-PhBox and Pr-
PhOLi/(–)-Sp initiators at [1b]/[initiator] ratio of 2 to inves-
tigate the degree of stereocontrol in the formation of an opti-
c
Determined by GPC as polystyrene standard. Degree of polymerization
(DP) is determined by 1H NMR.
d
In chloroform.
472
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
i
TABLE 4 Asymmetric Anionic Oligomerizations of 1a-c with PrPhOLi/(–)-PhBox Initiator
at –78 8Ca
Run
1
Monomer
Solvent
CH2Cl2
Time/h
12
Yield/%
[a]435 (ꢀ)b
1a (Me)
1-mer: 10.4
2-mer: 17.6
1-mer: 8.3
2-mer: 11.4
1-mer: 14.1
2-mer: 22.0
1-mer: 9.5
2-mer: 8.2
þ3.7
þ21.8
þ3.0
þ31.0
ꢂ6.0
þ26.2
ꢂ1.5
þ20.2
2
3
4c
a
1b (Et)
1c (nPr)
1b (Et)
CH2Cl2
CH2Cl2
12
12
12
CH2Cl2/toluene
(30/70 in vol %)
b
c
Conditions: [monomer] ¼ 0.23 mol/L, [Monomer]/
[Initiator] ¼ 2.
In chloroform.
Ref. 4.
for 1a, Figure 1(b) for 1b, and Figure 1(c) for 1c, respec-
tively, where top and bottom chromatograms were moni-
tored by CD and UV detectors, respectively.
52%/48% for 1b, and 49%/51% for 1c, respectively, leading
to enantiomer in a R-configurational 1-mer/S-configurational
1-mer ratio of 52/48 in mol % for 1a, 52/48 in mol % for
1b, and 49/51 in mol % for 1c. However, these very low ee
values for all of 1-mers indicate quite low stereoselectivity
in the initiation step.
In Figure 1, the 1-mer with a positive CD sign was first
eluted and followed by the 1-mer with a negative CD one,
indicating that both components are enantiomers. On the ba-
sis of the peak area obtained from the UV chromatograms in
Figure 1, a ratio of the first-eluted component (1-mer with a
positive CD sign)/the second-eluted one (1-mer with a nega-
tive CD sign) in the enantiomers is determined to be 52/48
in mol % for 1a, 52/48 in mol % for 1b, and 49/51 in mol
% for 1c, respectively. The absolute configuration of the chi-
ral carbon in the 1-mer has not been determined yet. Here,
assuming that the first-eluted component (1-mer with a posi-
tive CD sign) has a chiral carbon of a R-configuration and
the second-eluted one (1-mer with a negative CD sign) does
a chiral carbon of a S-configuration, 1-mer with the R-config-
urational chirality is formed in a slight excess amount in
comparison to 1-mer with the S-configurational one for 1a
and 1b, but in a slight less amount for 1c, respectively, and
the enantiomeric excess (ee) is calculated to be 4% ee(R) for
1a, 4% ee(R) for 1b, and 2% ee(S) for 1c, respectively. This
indicates that, as shown in Scheme 3, addition of a lithium
4-isopropylphenoxide anion coordinated with a (–)-PhBox
ligand to the monomer takes place in Re-face (front side)
attack/Si-face (back side) attack ratio of 52%/48% for 1a,
Next, to examine the stereoselectivity in the 2-mer, optical
resolution of the 2-mer was conducted with HPLC analysis
like the 1-mer. The chromatograms of the optical resolution
of the 2-mer obtained by oligomerizations are shown in Fig-
ure 2(a) for 1a, Figure 2(b) for 1b, and Figure 2(c) for 1c,
respectively, where four diastereomers are separated com-
pletely for 1a and 1b, but not for 1c though we attempted
to separate them in various conditions.
From the peak area obtained on the UV chromatograms in
Figure 2, the ratios of the first-eluted component with a pos-
itive CD sign/the second-eluted one with a negative CD sign/
the third-eluted one with a positive CD sign/the fourth-
eluted one with a negative CD sign were determined to be
32/21/29/18 in mol % for 1a and 37/20/29/14 in mol %
for 1b, respectively. For 1c, as the peaks of the first-eluted
and second-eluted components overlap, the ratio of the first-
eluted component/second-eluted one was determined by
nonlinear peak separation using Gaussian function, and the
ratios of the first-eluted component with a negative CD sign/
FIGURE 1 HPLC chromatograms of optical resolution of the 1-mers obtained by oligomerizations of (a) 1a, (b) 1b, and (c) 1c with
the iPrPhOLi/(–)-PhBox initiator (column: Daicel Chiralpak AD, eluent: hexane/ethanol ¼ 90/10 (in vol %), flow rate: 0.5 mL/min).
The top chromatogram was measured by CD detector (235 or 220 nm) and bottom by UV detector (235 or 220 nm).
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479
473

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
rations. On the assumption in optical resolution of the 1-mer
that the 1-mer with a R-configuration is first eluted and fol-
lowed by the 1-mer with a S-configuration, the 2-mer with a
(R,R)-configuration might be eluted faster than that with a
(R,S)-configuration. The first-eluted, the second-eluted, the
third-eluted, and the fourth-eluted components in the chro-
matograms for 2-mers of 1a [Fig. 2(a)] and 1b [Fig. 2(b)]
could be assigned reasonably in turn to the 2-mers with a
(R,R)-configuration, a (R,S)-one, a (S,R)-one, and a (S,S)-one,
respectively. On the other hand, for 1c [Fig. 2(c)] the first-
eluted, the second-eluted, the third-eluted, and the fourth-
eluted components could be assigned to the 2-mer with a
(S,R)-configuration, a (R,R)-one, a (S,S)-one, and a (S,R)-one,
respectively, on the basis of their CD signs, which are oppo-
site to those for 1a and 1b (a positive CD sign for first-
eluted component, a negative CD sign for second-eluted one,
a positive CD sign for third-eluted component and a negative
CD sign for fourth-eluted one). On the basis of this assign-
ment, for 1a, the 2-mers with a (R,R)-configuration (32 mol
%) and with a (S,R)-configuration (29 mol %) are produced
in larger amount by a factor of 1.6 than those with a (R,S)-
configuration (21 mol %) and with a (S,S)-configuration (18
mol %), respectively, and also the diastereomeric excess (de)
is calculated to be 21% de(RR/RS) for the 1-mer with a R-
configuration and 23% de(SR/SS) for the 1-mer with a S-con-
figuration, respectively. Addition reaction of the 1-mer anion
to a monomer 1a might take place stereoselectively regard-
less of the configurational chirality in a 1-mer anion to pro-
duce a 2-mer with an excessive R-configurational chiral car-
bon (32 mol % þ 29 mol % ¼ 61 mol %) in comparison
with the S-configurational chiral carbon (21 mol % þ 18
mol % ¼ 39 mol %). Probably, the propagation reaction to
3-mer, 4-mer, 5-mer, and oligomer, and polymer is consid-
ered to proceed in same stereoselectivity (R-configuration/S-
configuration ¼ 61/39 in mol %). Stereoselectivity on the
initiation and propagation reactions for the polymerization
SCHEME 3 Stereoselectivity in the addition reaction of the iPr-
PhOLi/(–)-PhBox initiator to monomer in the initiation step.
the second-eluted one with a positive CD sign/the third-
eluted one with a negative CD sign/the fourth-eluted one
with a positive CD sign were estimated to be 20/35/14/31
in mol % for 1c.
Here, addition of enantiomers in the 1-mer to monomer
might form four diastereomers in the 2-mer as shown in
Chart 1.
On the basis of the result of the optical resolution of the 1-
mer for 1a, we considered that total amount of the 2-mer
with (R,R)- and (R,S)-configurations derived from the R-con-
figurational 1-mer is 52 mol %, and total amount of the 2-
mer with (S,R)- and (S,S)-configurations derived from the S-
configurational 1-mer is 48 mol %, respectively. In the UV
chromatogram of the 2-mer in Figure 2(a), total amount of
the first-eluted (32 mol %) and the second-eluted (21 mol
%) components is 53 mol % and also total amount of the
second-eluted (21 mol %) and the third-eluted (29 mol %)
components is 50 mol %, respectively. Therefore, a combina-
tion of the first-eluted and the second-eluted components
might be assigned to the 2-mer with (R,R)- and (R,S)-configu-
i
of 1a with the PrPhOLi/(–)-PhBox initiator is summarized in
Chart 2.
For 1b, the 2-mers with a (R,R)-configuration (37 mol %)
and with a (S,R)-configuration (29 mol %) are produced in
FIGURE 2 HPLC chromatograms of optical resolution of the 2-mers obtained by oligomerizations of (a) 1a (b) 1b, and (c) 1c with
the iPrPhOLi/(–)-PhBox initiator (column: Daicel Chiralpak AD, eluent: hexane/ethanol ¼ 90/10 (in vol %), flow rate: 0.5 mL/min).
The top chromatogram was measured by CD detector (235 or 220 nm) and bottom by UV detector (235 or 220 nm).
474
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
CHART 1 Diastereomers of the 2-mer.
larger amount by a factor of 1.9 than those with a (R,S)-con-
figuration (20 mol %) and with a (S,S)-configuration (14 mol
%), respectively, and also the diastereomeric excess (de) is
calculated to be 30% de(RR/RS) for the 1-mer with a R-con-
figuration and 35% de(SR/SS) for the 1-mer with a S-config-
uration, respectively. Addition reaction of the 1-mer anion to
a monomer 1b might take place stereoselectively to produce
a 2-mer with a R-configurational chiral carbon (37 mol % þ
29 mol % ¼ 66 mol %) in excess with respect to a 2-mer
with a S-configurational chiral carbon (20 mol % þ 14 mol
% ¼ 34 mol %). Probably, the propagation reaction to 3-
mer, 4-mer, 5-mer, and oligomer, and polymer is considered
to proceed in same stereoselectivity (R-configuration/S-con-
figuration ¼ 66/34 in mol %) as well as the case of 1a. Ste-
reoselectivity on the initiation and propagation reactions for
the polymerization of 1b with the PrPhOLi/(–)-PhBox initia-
tor is summarized in Chart 3.
i
For 1c, the 2-mers with a (R,R)-configuration (35 mol %)
and with a (S,R)-configuration (31 mol %) are produced in
larger amount by a factor of 1.9 than those with a (R,S)-con-
figuration (20 mol %) and with a (S,S)-configuration (14 mol
%), respectively, and also the diastereomeric excess (de) is
calculated to be 27% de(RR/RS) for the 1-mer with a R-con-
figuration and 38% de(SR/SS) for the 1-mer with a S-config-
uration, respectively. Addition reaction of the 1-mer anion to
a monomer 1c might take place stereoselectively to produce
a 2-mer with a R-configurational chiral carbon (35 mol % þ
CHART 2 Stereoselectivity on the initiation and propagation reactions for the polymerization of 1a with the iPrPhOLi/(–)-PhBox
initiator.
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479
475

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
CHART 3 Stereoselectivity on the initiation and propagation reactions for the polymerization of 1b with the iPrPhOLi/(–)-PhBox
initiator.
31 mol % ¼ 66 mol %) in excess with respect to a 2-mer
with a S-configurational chiral carbon (20 mol % þ 14 mol
% ¼ 34 mol %). Probably, the propagation reaction to 3-
mer, 4-mer, 5-mer, and oligomer, and polymer is considered
to proceed in same stereoselectivity (R-configuration/S-con-
figuration ¼ 66/34 in mol %) as well as the case of 1a and
1b. Stereoselectivity on the initiation and propagation reac-
ment of the stereoselectivity on the addition reaction of the
1-mer anion to the monomer. Furthermore, the extent of ste-
reoselectivity of 2-mers for 1b and 1c were clearly higher
than that of 2-mer for 1a. As the results, the polymers with
higher molar optical rotation around 100ꢀ were obtained by
asymmetric anionic polymerization of 1b and 1c. When the
oligomerization of 1b was carried out in a mixture solution
of dichloromethane/toluene (30/70 in vol %), 1-mer with S-
configurational chirality was formed in a slight excess
amount compared to 1-mer with R-configurational one,
which is the reverse of the result in the dichloromethane. It
is considered, therefore, that, in a mixture solution of
dichloromethane/toluene (30/70 in vol %) containing tolu-
ene as a less polar solvent, some change of the distance
between the initiator anion and the counterion might take
place, and the change might exert a influence on the coordi-
nation structure involving a chiral ligand.
i
tions for the polymerization of 1c with the PrPhOLi/(–)-
PhBox initiator is summarized in Chart 4.
Stereoselectivities of 1-mer and 2-mer in the oligomeriza-
tions of 1a-c with the iPrPhOLi/(–)-PhBox initiator in
dichloromethane at –78 ꢀC are summarized in Table 5, to-
gether with the previous result of 1b in a mixture solution
4
ꢀ
of dichloromethane/toluene (30/70 in vol%) at –78 C.
These results indicate that, in the initiation reaction step,
stereoselective addition reactions of the initiator to mono-
mers hardly take place, and the effect of alkoxy groups such
as methoxy, ethoxy, and n-propoxy groups was scarcely
observed in the stereoselectivity of 1-mers. While, in the
propagation reaction step, relatively high stereoselectivity is
observed. This indicates that, in the formation of dimer, the
alkoxycarbonyl group of the monomers exerts the improve-
Effect of Counterion and Solvent on the Stereocontrol
We investigated the effects of a counterion such as lithium,
sodium, and potassium in the initiator, solvent, and a chiral
ligand such as (–)-Sp and (–)-PhBox on the specific optical
rotation of the polymers. Asymmetric anionic polymerizations
CHART 4 Stereoselectivity on the initiation and propagation reactions for the polymerization of 1c with the iPrPhOLi/(–)-PhBox
initiator.
476
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
TABLE 5 Stereoselectivity on the Initiation and Propagation Reactions in Asymmetric Anionic
i
Polymerizations of 1a-c with the PrPhOLi/(–)-PhBox Initiator
Initiation Reaction
Propagation Reaction
Run
1
Monomer
Solvent
CH2Cl2
1-mer (R:S)
2-mer (R:S)
1a (Me)
4% ee (R) (52:48)
4% ee (R) (52:48)
2% ee (S) (49:51)
4% ee (S) (48:52)
21% de (RR/RS)
23% de (SR/SS)
(R:S ¼ 61:39)
30% de (RR/RS)
35% de (SR/SS)
(R:S ¼ 66:34)
2
1b (Et)
1c (nPr)
1b (Et)
CH2Cl2
CH2Cl2
3
27% de (RR/RS)
38% de (SR/SS)
(R:S ¼ 66:34)
4a
CH2Cl2/toluene
(30/70 in vol %)
36% de (RR/RS)
32% de (SR/SS)
(R:S ¼ 57:43)
a
Ref. 4.
of 1b were carried out in dichloromethane and in a mixture
solution of dichloromethane/toluene (30/70 in vol %) at –78
ꢀC, and the results are summarized in Table 6 for the iPrPhOM
tors increase in changing from a polar solvent such as
dichloromethane to a less polar solvent such as a mixture so-
lution of dichloromethane/toluene (30/70 in vol %),
although their values are relatively small. Generally, it is well-
known that in anionic polymerizations in less or non polar
solvents the dissociation of carbanion center and counterion
is suppressed and favors to ion pair formation.7 It is, there-
fore, considered that dissociation between the carbanion and
the counterion is in a small degree in a mixture solution of
dichloromethane/toluene (30/70 in vol %) containing tolu-
ene as a less polar solvent and favors ion pair formation to
free ion, leading to improvement of stereoselectivity in the
addition reaction.
i
(M ¼ Li, Na, K)/(–)-Sp initiator and Table 7 for the PrPhOM
(M ¼ Li, Na, K)/(–)-PhBox initiator, respectively.
i
i
Polymerizations of 1b with PrPhONa/(–)-Sp and PrPhOK/(–)
-Sp initiators afford the corresponding polymers with high
molecular weights of 12,500–54,800 in high yields of
83–89% in both solvents, dichloromethane and a mixture so-
lution of dichloromethane/toluene (30/70 in vol %). The
i
i
polymers obtained with PrPhONa/(–)-Sp and PrPhOK/(–)-Sp
initiators in both solvents have much higher molecular
i
weights than those obtained with PrPhOLi/(–)-Sp initiator,
i
indicating that the polymerizations with PrPhONa/(–)-Sp and
Polymerizations of 1b with iPrPhOLi/(–)-PhBox initiator
affords corresponding polymers with the molecular weights
of 2700 in dichloromethane and 1600 in a mixture solution
of dichloromethane/toluene (30/70 in vol %). The specific
optical rotation values of polymers obtained in dichlorome-
thane and in a mixture solution of dichloromethane/toluene
(30/70 in vol %) are þ53.6ꢀ and þ91.8ꢀ, respectively. While,
polymerizations of 1b with iPrPhONa/(–)-PhBox initiator
iPrPhOK/(–)-Sp initiators would take place in much faster
propagation reaction than initiation one, that is, suggesting
that in the cases of Naþ and Kþ as a counterion the polymer-
ization would proceed in much higher degree of dissociation
state between the carbanion center and the counterion rela-
tive to the case of Liþ as a counterion. The specific optical
rotation values of polymers obtained with all of three initia-
i
TABLE 6 Asymmetric Anionic Polymerization of 1b with PrPhOM/(–)-Sp Initiatorsa
Yield/%b
Mn
Mw/Mn
[a]435
c
c
d
Counter Cation
Solvent
Time/h
Liþ
Naþ
Kþ
Liþ
Naþ
Kþ
a
CH2Cl2
48
24
24
48
48
48
99
88
88
77
89
83
3,100
23,400
12,500
1,700
1.40
1.26
1.68
1.43
1.26
1.68
ꢂ1.2ꢀ
ꢂ0.14ꢀ
ꢂ1.1ꢀ
ꢂ2.3ꢀ
ꢂ6.9ꢀ
ꢂ4.0ꢀ
CH2Cl2
CH2Cl2
CH2Cl2/toluene (30/70)
CH2Cl2/toluene (30/70)
CH2Cl2/toluene (30/70)
21,000
54,800
c
[Monomer] ¼ 0.23 mol/L, [Monomer]/[Initiator] ¼ 20, Temp. –78 ꢀC.
Determined by GPC as polystyrene standard.
In chloroform.
b
d
Hexane-insoluble part.
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479
477

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
i
TABLE 7 Asymmetric Anionic Polymerization of 1b with PrPhOM/(–)-PhBox Initiatorsa
Yield/%b
Mn
Mw/Mn
[a]435
c
c
d
Counter Cation
Solvent
Time/h
Liþ
Naþ
Kþ
Liþ
Naþ
Kþ
a
CH2Cl2
48
24
96
49
88
30
39
87
2,700
12,500
12,500
1,600
1.36
1.15
1.16
1.26
1.17
1.24
þ53.6ꢀ
þ8.6ꢀ
ꢂ1.1ꢀ
þ91.8ꢀ
ꢂ3.0ꢀ
ꢂ3.2ꢀ
CH2Cl2
CH2Cl2
24
CH2Cl2/toluene (30/70)
CH2Cl2/toluene (30/70)
CH2Cl2/toluene (30/70)
48
236
168
6,200
17,600
c
[Monomer] ¼ 0.23 mol/L, [Monomer]/[Initiator] ¼ 20, Temp. –78 ꢀC.
Determined by GPC as polystyrene standard.
In chloroform.
b
d
Hexane-insoluble part.
proceed in slow rate, and afford corresponding polymers in
low yields in both solvents. Polymerization with PrPhONa/
It is pointed out that Liþ in the asymmetric anionic polymer-
izations of substituted quinine methides is the most effective
counterion.
i
(–)-PhBox initiator yielded a positive specific optical rotation
value of þ8.6ꢀ in dichloromethane and a negative one of –
3.0ꢀ in a mixture solution of dichloromethane/toluene (30/
70 in vol %), respectively, and these values are much smaller
than those of the polymers obtained with iPrPhOLi/(–)-
PhBox initiator in both solvents. Moreover, the polymers
obtained in both solvents showed an opposite sign each
other, and also the optical rotation values became smaller in
addition of toluene as a less polar solvent into dichlorome-
thane. It is unclear why the stereochemical result reverses
with solvent at present. It is speculated that a counterion
Naþ is brought to the vicinity of the carbanion center by
addition of less polar solvent, and the bulkiness of the Naþ
influences to the coordination of a chiral ligand, resulting to
less stereoselectivity in the addition reaction. Polymeriza-
CONCLUSIONS
Molar optical rotation values of the polymer obtained by the
polymerizations of 1a-j with chiral initiators were signifi-
cantly dependent upon alkoxy groups, and they decreased
with an increase in the bulkiness of the alkoxy groups. Poly-
i
merization of 1b (Et) with PrPhOLi/(–)-PhBox afforded the
polymer with a maximum value of molar optical rotation,
and the ethoxy group was found to be the most suitable sub-
stituent for the stereocontrol of the polymer. From optical
resolutions of 1-mer and 2-mer in the oligomers obtained by
asymmetric oligomerizations of
1
monomers having
methoxy(1a), ethoxy(1b), and n-propoxy(1c) groups with
chiral initiators, stereoselectivity was hardly observed at the
initiation reaction, but it was observed at the propagation
reaction, where higher stereoselectivity was observed in the
monomers with ethoxy and n-propoxy groups. In asymmetric
i
tions of 1b with PrPhOK/(–)-PhBox initiator in both sol-
vents afford the corresponding polymers with high molecular
weights in high yields in comparison with the cases of the
i
i
polymerizations with PrPhONa/(–)-PhBox initiator. However,
anionic polymerizations of 1b with PrPhOM(M ¼ Li, Na, K)/
i
i
the polymers obtained with PrPhOK/(–)-PhBox initiator in
(–)-Sp and PrPhOM(M ¼ Li, Na, K)/(–)-PhBox initiators, it
was found that the initiator having Naþ as a counterion is
effective for the stereocontrol of the polymer in dichlorome-
thane/toluene (30/70 in vol%) for (–)-Sp as a ligand, and
also the initiator having a smaller Liþ as a counterion is
effective in both dichloromethane and dichloromethane/tolu-
ene (30/70 in vol%) for (–)-PhBox as a ligand.
both solvents have much smaller specific optical rotation val-
i
ues relative to those with PrPhOLi/(–)-PhBox initiator and
iPrPhONa/(–)-PhBox initiator, and also they have the optical
rotation values with negative signs. As ion radius and polar-
ity of Kþ are larger than those of Liþ and Naþ, Kþ counter-
ion is considered to exist apart from the carbanion, that is,
the carbanion that Kþ is a conterion would be present in a
free ion state in comparison with Liþ and Naþ. It is plausi-
ble, therefore, that in the addition of the anion to monomer
the (–)-PhBox ligand does not work effectively, or there is a
possibility that the chiral ligand does not coordinate to Kþ
as an extreme case.
This work was supported by Grant-in-Aid for Scientific
Research (No. 18350062 and No. 22550110) from the Ministry
of Education, Culture, Sports, Science and Technology, Japan.
The authors acknowledge Prof. Yoshio Okamoto, Nagoya Uni-
versity, for optical resolution of oligomers.
i
From the investigation of the counterion effect in the Pr-
PhOM(M ¼ Li, Na, K)/(–)-PhBox initiators for the polymer-
REFERENCES AND NOTES
i
ization of 1b, it was found that the PrPhOLi/(–)-PhBox ini-
tiator having Liþ as a counterion is more effective on the
stereocontrol in roder to obtain the optically active polymer
in comparison with other two initiators having Naþ and Kþ
as a counterion. Organic lithium initiators are widely used as
the stereospecific polymerization catalysts for styrene,8 1,3-
dienes such as 1,3-butadiene and isoprene,9 and acrylates.10
1 (a) Okamoto, Y.; Nakano, T. Chem. Rev. 1994, 94, 349–372;
(b) Green, M. M.; Peterson, N. C.; Sato, T.; Teramoto, A.; Cook,
R.; Lifson, S. Science 1995, 268, 1860–1860; (c) Nakano, T.; Oka-
moto, Y. Chem. Rev. 2001, 101, 4013–4038; (d) Cornelissen, J.
J. L. M.; Rowan, A. E.; Nolte, R. J. M.; Sommerdijk, N. A. J. M.
Chem. Rev. 2001, 101, 4039–4070; (e) Fujiki, M. Macromol.
Rapid Commun. 2001, 22, 539–563; (f) Yashima, E.; Maeda, K.
478
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
Macromolecules 2008, 41, 3–12; (g) Yashima, E.; Maeda, K.;
Iida, H.; Furusho, Y.; Nagai, K. Chem. Rev. 2009, 109,
6102–6211; (h) Sakamoto, T.; Fukuda, S.; Sato, S.; Nakano, T.
Angew. Chem. Int. Ed. 2009, 48, 9308–9311; (i) Oishi, T.; Oni-
mura, K.; Isobe, Y.; Yanagihara, H.; Tsutsumi, H. J. Polym. Sci.
Part A: Polym. Chem. 2000, 36, 310–320; (j) Onimura, K.; Tsut-
sumi, H.; Oishi, T. Macromolecules 1998, 31, 5971–5976;
(k) Isobe, Y.; Onimura, K.; Tsutsumi, H.; Oishi, T. Macromole-
cules 2001, 34, 7617–7623.
6 Itoh, T.; Nomura, S.; Saitoh, N.; Uno, T.; Kubo, M.; Sada, K.;
Inoue, K.; Miyata, M. Macromolecules 2004, 37, 7938–7944.
7 Odian, G. In Principles of Polymerization, 3rd ed.; Wiley: New
York, 1991; Chapter 5, pp 356–440.
8 (a) Braun, D.; Herner, M.; Kern, W. Makromol. Chem. 1960,
36, 232–243; (b) Kern, R. J. Nature 1960, 187, 410–411;
(c) Kawamura, T.; Uryu, T.; Matsuzaki, K. Makromol. Chem.
1982, 183, 153–162.
9 (a) Morton, M. In Anionic Polymerization: Principles and
Practice; Academic Press: New York, 1983; Chapter 7, pp 147–
164; (b) Van Beylen, M.; Bywater, S.; Smets, G.; Szwarc, M.;
Worsfold, D. J. Adv. Polym. Sci. 1988, 86, 87–143.
2 (a) Yuki, H.; Okamoto, Y.; Okamoto, I. J. Am. Chem. Soc.
1980, 102, 6356–6358; (b) Okamoto, Y.; Honda, S.; Okamoto, I.;
Yuki, H. J. Am. Chem. Soc. 1981, 103, 6971–6973; (c) Nakano,
T. J. Chromatogr. A 2001, 906, 205–225.
10 (a) Bywater, S. In Carbanionic Polymerization: Polymer
Configuration and the Stereoregulation Process; in Compre-
hensive Polymer Science; Eastmond, G. C.; Ledwith, A.; Russo,
S.; Sigwalt, P., Eds.; Pergamon Press: Oxford, 1989; Vol. 3,
Chapter 28, pp 435–860; (b) Pasquon, I.; Porri, L.; Giannini, U.
In Encyclopedia of Polymer Science and Engineering, 2nd ed.;
Mark, H. F.; Bikales, N. M.; Overberger, C. G.; Menges, G. Eds.;
Wiley-Interscience: New York, 1989; Vol. 15, pp 632–763.
3 Nakagaki, N.; Uno, T.; Kubo, M.; Itoh, T. J. Polym. Sci. Part
A: Polym. Chem. 2009, 47, 5923–5927.
4 Iizuka, S.; Nakagaki, N.; Uno, T.; Kubo, M.; Itoh, T. Macromo-
lecules 2010, 43, 6962–6967.
5 Iwatsuki, S.; Itoh, T.; Meng, X. Macromolecules 1993, 26,
1213–1220.
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 466–479
479