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CHAPTER 13

SYNTHESIS OF HYPERBRANCHEDPOLYMER HAVING BINAPHTHOLUNITS VIA OXIDATIVECROSS-COUPLING POLYMERIZATION

SHIGEKI HABAUE

13.1 INTRODUCTION

The hyperbranched polymers and dendrimers are highly branched macromolecules

having unique three-dimensional structures with a large number of terminal groups;

therefore, have attracted considerable attention because of their interesting chemical

and physical properties and potential applications [1–10]. In particular, the hyper-

branched polymers are a polydispersed macromolecule with a randomly branched

structure, and they can be easily produced on a large scale and by a one-step

polymerization process using the ABx-type monomers (x� 2), where the reaction

between the A and B groups takes place. Compared with their linear analogs, the

hyperbranched polymers possess a good solubility in organic solvents, lower

viscosity, etc. [1, 2, 10].

Axially dissymmetric 1,1’-bi-2-naphthol derivatives are very important and ver-

satile chiral auxiliaries, and they have been extensively used in asymmetric synthesis,

catalyses, and resolutions. Polymers with binaphthol units are also interesting as

functional chiral materials, and numerous reports can be found on their syntheses and

applications [11–16]. For example, optically active 1,1’-binaphthyl-based polymers,

as well as racemic ones, have been studied as electroluminescent materials

because the conjugation length of a polymer could be controlled without inserting

a nonconjugated spacer group into the polymer main chain [11, 15, 16].

From these points of view, there has been an intense interest in the preparation of

the optically active binaphthols. The oxidative coupling reaction of the 2-naphthol

derivatives is a facile and effective method for their synthesis, and many studies on

Polymeric Chiral Catalyst Design and Chiral Polymer Synthesis, First Edition. Edited by Shinichi Itsuno.� 2011 John Wiley & Sons, Inc. Published 2011 by John Wiley & Sons, Inc.

389

the homo- or self-coupling reaction with chiral metal catalysts, such as V(IV), Ru(II),

and Cu(I), producing a symmetrical binaphthol skeleton have been reported [11–13,

17–24]. In contrast, there have been few reports on the synthesis of the binaphthol

derivatives having an unsymmetrical framework through the catalytic cross-coupling

reaction [25–29]. The oxidative coupling reaction of a 1:1 mixture of naphthol 1 and

hydroxynaphthoate 2 can afford a mixture of the three coupling products, two of

which are obtained by the homo-coupling of 1 and 2 (X and Z), respectively, and one

by cross-coupling (Y) (Scheme 13.1). For example, Kozlowski et al. reported that the

oxidative coupling reaction of 2-naphthol 1a and methyl 3-hydroxy-2-naphthoate 2a

with the CuBF4-(S,S)-1,5-diaza-cis-decalin catalyst resulted in a poor yield (8%) of

the cross-coupling product with an enantioselectivity of 72%ee (R) [30, 31].

We found that the oxidative coupling reaction between two differently substituted

2-naphthol derivatives, 1 and 2, with the CuCl-(S)-2,2’-isopropylidenebis(4-phenyl-

2-oxazoline) [(S)Phbox] (Scheme 13.2) catalyst at room temperature under an O2

atmosphere proceeded in a highly cross-coupling selective manner [32–34]. This

method was further used for the polymerization of the 6,6’-dihydroxy-2,2’-bi-

naphthalene-7-carboxylic acid derivatives as a monomer leading to a polymer with

unsymmetrical binaphthol units [34–37].

The hyperbranched polymers have been mainly produced by polycondensation

reactions [1, 2, 38–40]. However, there is no report on their synthesis via the

oxidative coupling reaction of 2-naphthol derivatives, to the best of our knowledge.

The aforementioned cross-coupling reaction could be successfully applied to the

hyperbranched polymer synthesis. That is, the monomer has an AB2-type structure,

where the naphthol and hydroxynaphthoate moieties correspond to the A and B

SCHEME 13.1. Oxidative coupling reaction between 1 and 2.

390 SYNTHESIS OF HYPERBRANCHED POLYMER HAVING BINAPHTHOL UNITS

groups, respectively, and cross-coupling–specific polymerization of this monomer

can produce the hyperbranched structure with unsymmetrical binaphthol units [41].

13.2 OXIDATIVE CROSS-COUPLING REACTION BETWEEN2-NAPHTHOL AND 3-HYDROXY-2-NAPHTHOATE

The results of the oxidative coupling reaction of 1 and 2 (1:1) using various Cu(I)

catalysts in tetrahydrofuran (THF) under an O2 atmosphere are summarized in

Table 13.1 [32, 33]. During the reaction between 1a and 2a with (þ)-1-(2-pyrrolidi-

nylmethyl)pyrrolidine [(þ)PMP] (Scheme 13.2), which is known as the conventional

SCHEME 13.2. Various ligands for copper catalyst.

TABLE 13.1. Oxidative coupling reaction between 1 and 2 with Cu catalysta

Run 1 2 Catalyst (equiv.)

Time

(h)

Coupling

ratiob X:Y:Z

Cross-coupling

product (Y)

3

yield

(%)c ee (%)d

1 1a 2a CuCl-(þ)PMP (0.2) 48 2:38:60 3a 9 2 (S)

2 1a 2a CuCl-(�)Sp (0.2) 5 6:94:<1 3a 14 74 (S)

3 1a 2a CuCl-(S)Phbox (0.2) 3 <1:96:4 3a 87 10 (S)

4 1a 2a CuCl-(S)Phbox (0.1) 6 0:97:3 3a 82 8 (S)

5 1a 2a CuCl-(S)Phbox (0.01) 24 0:>99:<1 3a 79 8 (S)

6 1a 2b CuCl-(S)Phbox (0.2) 3 5:86:9 3b 72 55 (R)

7 1b 2b CuCl-(S)Phbox (0.2) 3 13:85:2 3c 73 65 (R)

8 1b 2b CuCl-(S)Phbox (0.01) 24 12:86:2 3c 71 67 (R)

9e 1b 2b CuCl-(S)Phbox (0.05) 48 11:87:2 3c 70 70 (R)

10f 1b 2b CuCl-(S)Phbox (0.1) 72 13:85:2 3c 44 74 (R)

a Conditions: [1]/[2]¼ 1/1, solvent¼THF, temp.¼ rt, O2 atmosphere.bDetermined by 1H NMR analysis and isolated yields.c Isolated yield.dDetermined by HPLC analysis (Chiralpak AD).e Temp.¼ 0�C.f Temp.¼�40�C.

OXIDATIVE CROSS-COUPLING REACTION 391

ligand for the copper catalyst of the asymmetric oxidative homo-coupling of the

2-naphthol derivatives [22], the homo-coupling product of 2a (Z) was predominantly

afforded (run 1). The CuCl-(�)-sparteine [(�)Sp] complex preferentially produced a

cross-coupling compound 3a with a selectivity of 94% but in a poor yield (run 2).

These complexes did not work as the catalyst. In contrast, 3a was obtained in a good

yieldwithahighercross-couplingselectivityof96%,whenCuCl-(S)Phboxwasusedas

the catalyst (run 3). However, the product showed a low enantioselectivity.

With a decreasing molar ratio of the Phbox catalyst, the cross-coupling selectivity

increased with almost no decrease in the yield and the enantioselectivity (runs 4 and

5). The oxidative coupling with 1.0 mol% of CuCl-(S)Phbox proceeded in a cross-

coupling–specific manner with a 79% yield, demonstrating that the Phbox ligand is

significantly effective for the cross-coupling of the 2-naphthol derivatives.

The enantioselectivity during the cross-coupling reaction improved when the

phenyl ester 2b was used as a substrate. The reaction between 1b and 2b produced

a cross-coupling product 3c in a 65%ee (R) (run 7). By lowering the reaction

temperature to �40�C, the enantioselectivity was further improved to 74%ee (R)

(run10).Thestructureof theesteron the substrate2and the substituent at the3-position

of 1 significantly affects both the cross-coupling and the stereoselectivities [32, 33].

The catalytic oxidative cross-coupling reaction of 2-naphthol derivatives was

attained by using the CuCl-Phbox catalyst. However, we recently found that the a

catalytic amount of a Lewis acid, such as ytterbium trifluoromethansulfonate

[Yb(OTf)3], can further control the oxidative cross-coupling reaction between 1 and

2with the copper catalyst (Scheme 13.3) [42–44]. For example, the oxidative coupling

reaction of 1a and2a (1:1)with theCuCl(OH)-N,N,N’,N’-tetramethylethylenediamine

(TMEDA) [45, 46] (Scheme 13.2) in the presence of Yb(OTf)3 at room temperature

under an O2 atmosphere proceeded in a cross-coupling–specific manner with a good

yield, whereas the reaction in the absence of Lewis acid resulted in a low yieldwith the

cross-coupling selectivity of 88%. In this novel binary catalyst system, the yields of

the cross-coupling products, and stereoselectivities were significantly affected by the

structures of both the copper and the Lewis acid catalysts [42–44].

13.3 OXIDATIVE CROSS-COUPLING POLYMERIZATION AFFORDINGLINEAR POLY(BINAPHTHOL)

The catalytic oxidative cross-coupling reaction with CuCl-Phbox was used for the

controlled synthesis of poly(binaphthol)s [35, 37]. The monomers, 6,6’-dihydroxy-

SCHEME 13.3. Oxidative cross-coupling between 1 and 2 in the presence of Yb(OTf)3.


2,2’-binaphthalene-7-carboxylate 4, which has both naphthol and hydroxynaphtho-

ate moieties, were employed. The oxidative coupling polymerization of 4 produce

a polymer, in which three different 1,1’-bi-2-naphthol units can exist, that is,

two homo-coupling units (X and Z) and a cross-coupling one (Y) (Scheme 13.4).

The completely random polymerization leads to a polymer with the unit ratio,

X:Y:Z¼ 25:50:25, whereas the polymer having a head-to-tail sequence structure is

constructed via the cross-coupling–specific polymerization (X:Y:Z¼ 0:100:0).

The results of the oxidative coupling polymerization of 4 using the various copper

catalysts, at room temperature for 24 h, are listed in Table 13.2. The polymerization

with the TMEDA, (þ)PMP, and (�)Sp catalysts afforded a methanol-ethyl acetate-

1N HCl (2/1/0.3 v/v/v)-insoluble part with a relatively lower number average

molecular weight (Mn) in low-to-moderate yields (runs 1–3, 5, 8, and 10) or resulted

in no yield (run 6). The CuCl-(S)Phbox catalyst produced a polymer with a good

SCHEME 13.4. Oxidative coupling polymerization of 4.

OXIDATIVE CROSS-COUPLING POLYMERIZATION AFFORDING 393

yield and an Mn value of �4.5� 103 (runs 4, 7, 9, and 11). In particular, poly-4d,

which showed an Mn of 9.1� 103, is totally soluble in THF.

The circular dichroism (CD) analysis of the obtained polymers showed that poly-

4a, poly-4c, and poly-4d obtained with the (S)Phbox catalyst were determined to be

rich in the S-configuration, whereas the R-structure is preferentially constructed

during the polymerization of 4b [6, 35, 37]. These results are in good agreement with

those of the oxidative cross-coupling reaction of the corresponding 2-naphthol

derivatives as shown in Table 13.1.

The coupling ratio, X:Y:Z, was determined by the 1H NMR analysis of the

hydroxyl absorption intensities, and the details will be described later for the

hyperbranched polymers. The estimated coupling ratios are also shown in Table 13.2.

For the polymerization with the (S)Phbox catalyst, the cross-coupling reaction

predominantly proceeded with a coupling selectivity Y of �95%, which is much

higher than that observed for the polymerizations with the TMEDA, (þ)PMP, and

(�)Sp catalysts. In particular, the polymer obtained from 4c showed the highest

Y-selectivity of 99%. Accordingly, the poly(binaphthol) having an almost

complete head-to-tail sequence structure was successfully constructed by the

oxidative cross-coupling polymerization.

The coupling stereoselectivity was evaluated by the oxidative coupling reaction of

the model compounds, in which one hydroxyl group of the monomer is protected by

TABLE 13.2. Oxidative coupling polymerization of 4 with Cu catalysta

Run 4 Catalyst

Yieldb

(%)

Mn (� 103)

(Mw/Mn)c [a]D

d

Unit

ratioe

X:Y:Z

ee of

Y-unitf

(%)

1 4a CuCl(OH)-TMEDA 55 2.0 (1.3) — 18:79:3 —

2 4a CuCl-(þ)PMP 81 1.9 (2.3) �16 19:63:18 16 (R)

3 4a CuCl2-(�)Spg 22 1.7 (1.3) �19 14:85:1 5 (R)

4 4a CuCl-(S)Phbox 71 (47) 4.5 (2.8)h þ20 3:96:1 31 (S)

5 4b CuCl(OH)-TMEDA 62 3.4 (1.3) — 11:71:18 —

6 4b CuCl-(þ)PMP 0 — — — —

7 4b CuCl-(S)Phbox 91 (33) 5.0 (1.8) �15 3:95:2 10 (R)

8 4c CuCl(OH)-TMEDA 27i 3.5 (1.2) — 7:87:6

9 4c CuCl-(S)Phbox 78i 7.7 (1.3) þ40 0:99:1 28 (S)

10 4d CuCl(OH)-TMEDA 81 4.1 (1.2) — 12:87:1 —

11 4d CuCl-(S)Phbox 95 9.1 (2.3) þ55 0:97:3 30 (S)

aConditions: [4]/[catalyst]¼ 1/0.2, solvent¼THF, temp.¼ rt, time¼ 24 h, O2 atmosphere.bMethanol-ethyl acetate-1N HCl (2/1/0.3 v/v/v)-insoluble part. In parentheses, the values for the THF-

soluble and methanol-insoluble part are given.cDetermined by SEC in THF (polystyrene standard).d In THF at 25�C.eEstimated by 1H NMR analysis (DMSO-d6, 50

�C).fEvaluated from the model coupling reaction.g [4]/[CuCl2]/[(�)Sp]¼ 1/0.5/1, solvent¼methanol, N2 atmosphere.hMn¼ 1.2� 104, determined by 1H NMR analysis.iMethanol-ethyl acetate-1N HCl (1/3/0.4 v/v/v)-insoluble part.


the methoxymethyl group. The reaction can again afford two homo-coupling

products, 5 (X) and 7 (Z), and one cross-coupling product, 6 (Y) (Scheme 13.5).

The observed stereoselectivities for 6 obtained by the model reaction with the copper

catalysts are also listed in Table 13.2.

In every reaction with the Phbox catalyst, the corresponding cross-coupling

compound 6 was produced in good yield (�67%) with a high selectivity

(�89%). The obtained cross-coupling product having a phenyl ester group is rich

in the R-configration (10%ee), whereas the others preferentially have the S-structure

(28–31%ee). These results for the cross-coupling selectivity and the absolute

configuration are similar to those observed for the polymerization, supporting the

belief that the stereochemistry constructed during the polymerization should be

controlled to a degree similar to that of the model reaction.

However, the coupling reaction with (þ)PMP and (�)Sp for 48 h resulted in a

much lower cross-coupling selectivity [X:Y:Z¼ 46:36:18 for (þ)PMP, 42:46:12

for (�)Sp] than that observed for the polymerization. In these coupling reactions, the

homo-coupling product 7 is the most unfavorable, based on the observed

coupling selectivity. Therefore, during the first stage of the polymerization, both

the homo-coupling unit X and the cross-coupling unit Y should be mainly produced,

and then the cross-coupling reaction predominantly proceeds to afford polymers

because the homo-coupling reaction leading to the unit Z hardly occurs.

The observed stereoselectivities were lower than that observed for the reaction with

the Phbox catalyst.

SCHEME 13.5. Model compounds 5-7 for poly-4.

OXIDATIVE CROSS-COUPLING POLYMERIZATION AFFORDING 395

13.4 OXIDATIVE CROSS-COUPLING POLYMERIZATION LEADINGTO A HYPERBRANCHED POLYMER

The triphenylamine derivatives 8–10 were synthesized, and the compounds 9 and 10

have both the naphthol and hydroxynaphthoate moieties (Scheme 13.6) [41].

Therefore, the cross-coupling–specific polymerization of these two monomers can

construct a hyperbranched polymer structure, whereas the homo-coupling reaction

can form a cross-linkage during the polymerization. The results of the oxidative

coupling polymerization using the CuCl-Phbox catalyst at room temperature in THF

under an O2 atmosphere are summarized in Table 13.3.

During the polymerization of 8, the homo-coupling reaction between the 2-

naphthol units took place to afford a cross-linked polymer. The product yield

increased with the increasing polymerization time, whereas the THF-soluble part

of the obtained product significantly decreased (runs 1–3). For example, the 24 h

polymerization resulted in a 94% yield, in which the product is almost insoluble in

THF, and the THF-soluble fraction (2%) showed a lowMn value of 0.6� 103 (run 3).

During the polymerization of the monomer 9, the yield of the THF-soluble part

and theMn value of the obtained polymer were much higher than those observed for

the polymerization of 8 (runs 4–6). For example, the 1 h-polymerization afforded a

polymer in a good yield, whose THF-soluble fraction (46%) showed an Mn of

8.3� 103 (run 5). However, the polymerization for 24 h produced a polymer

including a large amount of the THF-insoluble fraction (run 6). Therefore, some

cross-linking reaction, that is, the homo-coupling reaction in addition to the cross-

coupling one, should occur during the polymerization of 9.

In contrast, the polymerization of 10 having one naphthol and two hydroxy-

naphthoate moieties resulted in a high yield, in which the product is fully soluble in

common organic solvents, such as THF and chloroform (runs 7 and 8). The polymer

obtained by the 1 h polymerization showed an Mn of 1.02� 104. These results

SCHEME 13.6. Monomers 8-9 for hyperbranched polymer synthesis.


suggest that the polymerization of 10 should proceed in a highly cross-coupling

selective manner.

In poly-9 and poly-10, three different units, two homo-coupling units (X and Z)

and a cross-coupling one (Y), can again exist (Scheme 13.7). The coupling ratio

TABLE 13.3. Oxidative coupling polymerization of 8–10 with CuCl-(S)Phboxa

Run Monomer Time (h) Yieldb (%)

Mn (� 103)

(Mw/Mn)c [a]D

dUnit

ratioeX:Y:Z

1 8 0.5 70 3.1 (1.4)f �29 —

2 8 1 83 (27) 1.1 (—) — —

3g 8 24 94 (2) 0.6 (—) — —

4 9 0.5 78 5.4 (1.9)h þ65 8:91:1

5 9 1 87 (46) 8.3 (1.8) þ74 6:92:2

6g 9 24 91 (15) 1.2 (—) — —

7 10 0.5 92 4.8 (2.0) þ52 0:>99:08i 10 1 95 10.2 (2.6) �54 0:99:1

aConditions: [monomer]/[catalyst]¼ 1/0.1, solvent¼THF, temp.¼ rt, time¼ 24 h, O2 atmosphere.bMethanol-1N HCl (9/1 v/v)-insoluble part. In parentheses, the values for the THF-soluble and methanol-

insoluble part are given.cDetermined by SEC in THF (polystyrene standard).d In THF at 25�C.eEstimated by 1H NMR analysis (DMSO-d6, 50

�C).fMn¼ 1.0� 104 (Mw/Mn¼ 3.2), determined by MALLS in THF.g [Monomer]/[catalyst]¼ 1/0.2.hMn¼ 6.7� 104 (Mw/Mn¼ 2.6), determined by MALLS in THF.iCatalyst: CuCl-(R)Phbox.

SCHEME 13.7. Structure of hyperbranched polymer.

OXIDATIVE CROSS-COUPLING POLYMERIZATION LEADING 397

X:Y:Z can be calculated from the 1H NMR analysis. Figure 13.1 demonstrates the1H NMR spectra of the hydroxyl protons region of the obtained polymers, together

with that of poly-4d prepared with the Phbox catalyst. The internal and terminal

hydroxyl protons with different chemical shifts appeared as shown in the figure. For

example, the coupling selectivity of poly-4d was determined to be X:Y:Z¼ 0:97:3

(Table 13.2, run 11).

The estimated coupling ratios for the obtained polymers are also listed in

Table 13.3. Poly-10 showed a Y-selectivity of 99% and higher (runs 7 and 8).

Therefore, these polymers must consist of a hyperbranched structure. During the

polymerization of 9, the cross-coupling reaction preferentially proceeded to produce

FIGURE 13.1. 1H NMR spectra of hydroxyl protons of (a) poly-4d (Table 2, run 11),

(a) poly-8 (Table 3, run 2), (b) poly-9 (Table 3, run 4), and (c) poly-10 (Table 3, run 7)

(in DMSO-d6, 50�C).


a polymer with a cross-coupling selectivity of 91–92% (runs 5 and 6), supporting

the fact that the homo-coupling also took place to form a cross-linkage. A part of the

poly-9 was then insoluble in common organic solvents.

Because poly-10 has a nearly ideal hyperbranched polymer structure, the number

average molecular weight can be calculated from the 1H NMR analysis. It was

determined to be 6.2� 103 (run 7) and 2.0� 104 (run 8). These values were

much higher than that estimated from the size exclusion chromatography (SEC)

analysis. This result again indicates that the polymers obtained by the oxidative

coupling polymerization of the monomer 10 have a spherical and hyperbranched

structure.

Figure 13.2 shows the CD spectra of the obtained polymers. The spectral pattern

indicates that poly-8 is rich in the R-structure, whereas the S-configuration is

predominantly constructed during the polymerization of the monomers 9 and 10.

This result is similar to that observed for the oxidative coupling polymerization of the

corresponding monomer 4d. Accordingly, the stereoselectivity during the oxidative

cross-coupling polymerization with the CuCl-(S)Phbox catalyst may be controlled

to a degree similar to that for the polymerization of 4d, which was estimated to be

30%ee (S) by the model coupling reaction.

FIGURE 13.2. CD spectra of (a) poly-8 (Table 3, run1), (b) poly-9 (run 4), and (c) poly-10

(run 7) (monomer unit, in THF).

OXIDATIVE CROSS-COUPLING POLYMERIZATION LEADING 399

13.5 PHOTOLUMINESCENCE PROPERTIES OF HYPERBRANCHEDPOLYMERS

To examine the UV-vis (UV) and fluorescence (FL) properties of the obtained

hyperbranched-type polymers (Table 13.3, runs 1, 4, and 7), the acetylation of the

hydroxyl groups was carried out to produce the acetylated polymers (Scheme 13.8):

poly-8(Ac) (Mn¼ 4.6� 103, Mw/Mn¼ 2.8), poly-9(Ac) (Mn¼ 5.7� 103, Mw/Mn

¼ 2.2), and poly-10(Ac) (Mn¼ 5.7� 103, Mw/Mn¼ 1.8). Poly-4d (Table 13.2, run

11) was also acetylated to afford poly-4d(Ac) (Mn¼ 1.5� 104, Mw/Mn¼ 4.3)

(Scheme 13.9). The model compounds, 8(MOM), 9(MOM), 10(MOM), and

4d(Ac), for these polymers were also prepared (Scheme 13.10).

The UV absorption and FL spectra of poly-4d(Ac) and its model 4d(Ac) in

chloroform are shown in Figure 13.3 and Figure 13.4. The UV spectral patterns of

these compounds were similar with a strong absorption around lmax¼ 270 nm,

whereas the FL spectral pattern of poly-4d(Ac) was different from that of 4d(Ac).

Poly-4d(Ac) exhibited red-shifted and broadened emission bands. The FL spectrum

of the poly-4d(Ac) film was also obtained, and the observed spectral pattern was

similar to that of the dilute solution. These results suggest that the polymer forms an

intermolecular excimer.

The UVabsorption spectra of poly-10(Ac) and its model 10(MOM) in chloroform

are depicted in Figure 13.5. The other polymers and models, such as poly-8(Ac),

poly-9(Ac), 8(MOM), and 9(MOM), also showed similar spectral patterns, and

these spectra showed two strong bands around 250 and 360 nm. Figure 13.6

SCHEME 13.8. Acetylated hyperbranched polymers.


demonstrates the FL spectra of the polymers and the model compounds measured at

an excitation wavelength of 360–370 nm. In contrast to the FL behavior of poly-4d(Ac) and its model of 4d(Ac), the spectral patterns of the polymers, such as poly-8

(Ac), poly-9(Ac), and poly-10(Ac), were similar to that observed for each model

SCHEME 13.9. Acetylated 4d and poly-4d.

SCHEME 13.10. Methoxymethylated 8–10.

PHOTOLUMINESCENCE PROPERTIES OF HYPERBRANCHED POLYMERS 401

compound. Poly-8(Ac) and 8(MOM) showed an emission of blue light, whereas

poly-9(Ac), poly-10(Ac), 9(MOM), and 10(MOM) exhibited an emission in the

green region around 470 nm. The FL spectral pattern of the poly-9(Ac) film was also

similar to that observed for the dilute solution. Accordingly, these results suggest that

the intermolecular excimer formation hardly takes place because of the characteristic

hyperbranched-type structure.

FIGURE 13.3. UVabsorption spectra of (a) poly-4d(Ac) and (b) 4d(Ac) (C¼ 1.0� 10�5M,

chloroform).

FIGURE 13.4. FL spectra of (a) poly-4d(Ac) (lexc¼ 313 nm) and (b) 4d(Ac) (lexc¼ 312 nm)

(C¼ 1.0� 105M, chloroform), and (c) poly-4d(Ac) (lexc¼ 313 nm) (thin film)

.


13.6 CONCLUSIONS

A highly cross-coupling selective oxidative coupling reaction between 2-naphthol

and 3-hydroxy-2-naphthoate derivatives using the CuCl-Phbox catalyst was devel-

oped. This reaction system was successfully used for the synthesis of poly(bi-

naphthol) and the hyperbranched polymer with binaphthol units. The polymerization

of the triphenylamine monomer having a naphthol and two hydroxynaphthoate

FIGURE 13.5. UV spectra of (a) poly-10(Ac) and (b) 10(MOM) (C¼ 1.0� 10�5M,

chloroform).

FIGURE 13.6. FL spectra of (a) poly-8(Ac) (lexc¼ 365 nm), (b) poly-9(Ac) (lexc¼ 365 nm),

(c) poly-10(Ac) (lexc¼ 370 nm), (d) 8(MOM) (lexc¼ 365 nm), (e) 9(MOM) (lexc¼ 365 nm),

(f) 10(MOM) (lexc¼ 360 nm) (C¼ 1.0� 10�5M, chloroform), and (g) poly-9(Ac) (lexc¼363 nm) (thin film).

CONCLUSIONS 403

moieties, with the CuCl-Phbox catalyst, proceeded in an almost cross-coupling–

specific manner to afford a polymer with a hyperbranched structure, which is fully

soluble in common organic solvents. The obtained polymer showed a characteristic

FL property based on the hyperbranched structure, which was different from that

observed for the corresponding linear polymer with binaphthol units.

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