Reversible Fixation and Release of Alcohols by a Polymer Bearing

May 24, 2012 - Kazuhide Morino, Atsushi Sudo, and Takeshi Endo*. Molecular Engineering Institute, Kinki University, 11-6 Kayanomori, Iizuka, Fukuoka ...
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Reversible Fixation and Release of Alcohols by a Polymer Bearing Vicinal Tricarbonyl Moieties and Its Application to Synthesis and Reversible Cross-Linking−De-Cross-Linking System of a Networked Polymer Kazuhide Morino, Atsushi Sudo, and Takeshi Endo* Molecular Engineering Institute, Kinki University, 11-6 Kayanomori, Iizuka, Fukuoka 820-8555, Japan S Supporting Information *

ABSTRACT: In this paper, we report reversible fixation and release of alcohols by a polystyrene derivative bearing acyclic vicinal tricarbonyl moieties (1) and its application to synthesis and reversible cross-linking-de-cross-linking system of a networked polymer. First the reversible fixation and release behavior of alcohols by an acyclic vicinal tricarbonyl compound, 1,3-diphenylpropanetrione (DPPT) as a model compound of 1 was investigated. On the basis of the results, the fixation of n-hexanol to 1 was carried out to provide the n-hexanol adduct of 1 (1-HexOH), which has a hemiacetal structure. On the other hand, heating 1-HexOH in vacuo enabled successful recovery of 1 to demonstrate the reversible nature of this system. Furthermore, the reaction of 1 with 1,6-hexanediol proceeded smoothly to give networked polymer, which could be decross-linked by heating at 50 °C in DMSO/H2O mixture. This result indicates that a novel reversible cross-linking−de-crosslinking system of networked polymer was constructed.

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INTRODUCTION Vicinal tricarbonyl compounds such as alloxan, 1,2,3-indanetrione, and 1,3-diphenylpropanetrione (DPPT) exhibit intriguing reactivity, because their central carbonyl group is activated by its adjacent two carbonyl groups. Various nucleophiles such as water, alcohols, amines, and thiols can react with the central carbonyl group of vicinal tricarbonyl compounds,1 leading to the syntheses of various compounds including heterocyclic compounds such as pyrrole and furan derivatives.2−5 On the other hand, to the best of our knowledge, systematical studies on the reaction of vicinal tricarbonyl compounds with nucleophiles have been hardly reported so far. Recently, we have reported the detailed hydration− dehydration behavior of DPPT, which is a typical acyclic tricarbonyl compound.6 The hydration of DPPT proceeded in organic solvents containing water and in solid state under moisturized air. On the other hand, the hydrate of DPPT underwent the dehydration by heating under nitrogen flow or reduced pressure. This reversible hydration−dehydration was accompanied by disappearance-and-recovery of the distinctive yellow color of DPPT due to the collapse-and-recovery of the sequence of the three carbonyl groups of DPPT, indicating the unique hydration−dehydration system capable of being observed by the naked eye. Furthermore, this characteristic feature of DPPT motivated us to design homopolymer and copolymers bearing a vicinal tricarbonyl structure that inherits the reversible nature of the reaction of DPPT with water (Scheme 1).6,7 As with DPPT, their tricarbonyl moieties underwent the hydration in organic solvents containing water © 2012 American Chemical Society

Scheme 1. Reversible Hydration−Dehydration of a Polystyrene Derivative Bearing Vicinal Tricarbonyl Moieties (1)

and in solid state under moisturized air to provide the corresponding polymers bearing 2,2-geminal diol structure and their dehydration readily proceeded by heating in vacuo. As mentioned above, vicinal tricarbonyl groups can also undergo the addition of alcohols.1 Wasserman et al. applied the intramolecular addition of alcohol with vicinal tricarbonyl moiety to the formation of dihydrofuranone carboxylate, which could be converted to substituted 3-hydroxy-2-furyl carboxylic acid esters.2,8 However, the reaction behavior of vicinal tricarbonyl compounds with alcohols has not been examined systematically, and particularly, there is no report for the Received: February 15, 2012 Revised: May 7, 2012 Published: May 24, 2012 4494

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Scheme 2. Reversible Fixation and Release of Alcohols by 1 and Its Application to Synthesis and Reversible Cross-Linking−DeCross-Linking System of a Networked Polymer

(m, Ph, 4H), 7.32−7.22 (m, Ph, 5H), 6.08 (s, OH, 1H), 4.63 (s, CH2, 2H); IR (ATR) 3359 (OH), 1683 (CO) cm−1. Anal. Calcd for (C22H18O4)10·H2O: C, 75.89; H, 5.27. Found: C, 75.86; H, 5.09. Release Behavior of BnOH from DPPT−BnOH. A typical experimental procedure was as follows. DPPT−BnOH (70 mg, 0.20 mmol) was dissolved in 2 mL of CDCl3 under a nitrogen atmosphere. The solution was transferred to an NMR tube. The sample was sealed, and left standing at 50 °C. The 1H NMR spectrum was then measured at ambient temperature at an appropriate time to estimate the conversion of DPPT−BnOH. Fixation of 1-Hexanol by 1. 1 (264 mg, 1.0 mmol) was dissolved in CHCl3 (0.5 mL). To the solution was added 1-hexanol (0.13 mL, 1.0 mmol), and the reaction mixture was stirred at ambient temperature (24−26 °C) under argon atmosphere. After 8 h, 1hexanol (0.26 mL, 2.1 mmol) was added, and the reaction mixture was then stirred for 12 h. To the solution was added anhydrous n-hexane (20 mL). The resulting precipitate was collected by filtration, washed with anhydrous n-hexane, and dried in vacuo overnight to obtain 1HexOH (348 mg, 98%). The addition reaction of 1 with ethanol was performed in the same way. Release of 1-Hexanol from 1-HexOH. 1-HexOH (100 mg) was heated at 100 °C at 12 h under reduced pressure to give 72 mg of 1 as a yellow powder in 94% yield. Synthesis of Networked Polymer by Addition Reaction of 1 with 1,6-Hexanediol. 1 (264 mg, 1.0 mmol) was dissolved in CHCl3 (0.5 mL). To the solution was added a CHCl3 solution (0.1 mL) containing 1,6-hexanediol (5.9 mg, 0.05 mmol), and the reaction mixture was stirred at ambient temperature (24−26 °C) under argon atmosphere. After 20 h, to the reaction mixture was added anhydrous CHCl3 (5 mL). The resulting precipitate was collected by filtration, washed with anhydrous CHCl3, and dried in vacuo at 60 °C for 12 h to obtain networked polymer (255 mg, 94%). De-Cross-Linking of Networked Polymer. Networked polymer (50 mg) was dispersed in DMSO/H2O (9/1, v/v), and the solution was stirred at 50 °C for 6 h under argon atmosphere. To the solution was added a large amount of H2O. The resulting precipitate was collected by filtration, washed with H2O, and dried in vacuo at 100 °C for 6 h to obtain 1 (45 mg, 96%).

elimination of alcohols from alcohol-adduct of vicinal tricarbonyl compounds. These facts prompted us to construct novel, reversible fixation and release system of alcohols by 1 (Scheme 2). Herein we describe our investigation on reversible fixation and release behavior of alcohols by 1 and DPPT as a model compound of 1. Furthermore, the reversible fixation and release behavior of diol by 1 was also described, which produced the novel, reversible cross-linking-de-cross-linking system of networked polymer (Scheme 2).

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EXPERIMENTAL SECTION

Materials. Chloroform-d (CDCl3) and dimethyl sulfoxide-d6 (DMSO-d6) were distilled over molecular sieves 4A (MS 4A). Chlorobenzene-d5 (PhCl-d5) was dried over MS 4A. Chloroform, benzyl alcohol, 1-hexanol, 2-hexanol, and 2-methyl-2-pentanol were distilled over CaH2. Phenol (Tokyo Kasei, Tokyo) was used as received. Anhydrous n-hexane, anhydrous ethanol, and 1,6-hexanediol were purchased from Wako Pure Chemical Industries (Osaka, Japan). 1,3-Diphenylpropanetrione (DPPT) and polymer bearing vicinal tricarbonyl moieties (1) were synthesized in the same way for the literature method.6 The number-average molecular weight of 1 was 1.9 × 104. Measurements. 1H NMR spectra were taken on a Varian Unity INOVA400 operating at 400 MHz with tetramethylsilane as an internal standard. IR spectra were recorded on a Thermo Scientific Nicolet iS10 spectrometer. The molecular weight (Mn) was estimated by size exclusion chromatography (SEC) on a Tosoh HLC8220system equipped with three consecutive polystyrene gel columns (Tosoh TSKgel SuperAW2500, SuperAW3000, and SuperAW4000 (6.0 mm i.d. × 15 cm)) and refractive index (RI) detector at 40 °C. The system was operated at a flow rate of 0.5 mL/min and DMF containing 10 mM LiBr was used as the eluent. The molecular weight calibration curve was obtained with polystyrene standards (Tosoh). Thermogravimetry (TGA) was performed with a Seiko Instrument Inc. TG-DTA 6200 with an aluminum pan under a 150 mL/min N2 flow at a heating rate of 10 °C/min. UV−vis spectra were measured with a JASCO V-570 spectrophotometer in a 1 cm quartz cell. Fixation Behavior of Alcohols by DPPT. A typical experimental procedure was as follows. DPPT (411 mg, 1.73 mmol) was dissolved in 0.43 mL of CDCl3 under an argon atmosphere. To the solution was added BnOH (0.18 mL, 1.74 mmol), and the solution was then transferred to an NMR tube. The 1H NMR spectrum was then measured at ambient temperature (24−26 °C) at an appropriate time to estimate the conversion of DPPT. Synthesis of DPPT−BnOH. DPPT (1.36 g, 5.71 mmol) was dissolved in CHCl3 (1.4 mL). To the solution was added BnOH (0.60 mL, 5.80 mmol), and the reaction mixture was stirred at ambient temperature (24−26 °C) for 20 h under argon atmosphere. To the solution was added anhydrous n-hexane (50 mL). The resulting precipitate was washed with anhydrous n-hexane under argon atmosphere and dried in vacuo overnight to obtain DPPT−BnOH (1.71 g, 4.94 mmol, 87%) as a white crystal: 1H NMR (400 MHz, CDCl3) δ 8.21−8.17 (m, Ph, 4H), 7.61−7.55 (m, Ph, 2H), 7.46−7.40

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RESULTS AND DISCUSSION Reversible Fixation and Release of Alcohols by DPPT (Model System). Before the investigation on reversible fixation and release behaviors of alcohols by 1, fixation and release behaviors of alcohols by DPPT as a model for the polymer system was examined (Scheme 3). First we investigated the reactivity of DPPT with benzyl alcohol (BnOH) by 1H NMR measurements. The 1H NMR spectrum of a concentrated chloroform-d (CDCl3) solution of DPPT (1.7 M) in the presence of BnOH ([DPPT]/[BnOH] = 1) after 3 h showed a characteristic peak at 8.2 ppm due to the aromatic protons of BnOH-adduct of DPPT (DPPT−BnOH) (Figure S1 in Supporting Information). Figure 1a shows the time-dependence of conversion of DPPT in the addition of 4495

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BnOH was carried out in anhydrous CHCl3 for 20 h. As a result, DPPT−BnOH was obtained as a white crystal in 87% yield as n-hexane-insoluble part. The structure of DPPT-BnOH was confirmed by IR, 1H NMR, UV−visible, and elemental analyses (see Supporting Information). Although the IR absorption derived from the central carbonyl group of DPPT was observed at 1720 cm−1, this absorption disappeared completely and new peak due to hydroxy group of hemiacetal structure appeared at 3359 cm−1 in the IR spectrum of DPPT− BnOH (Figure S2 in Supporting Information). The 1H NMR spectrum of DPPT−BnOH indicated two singlet signals at 6.08 and 4.63 ppm, which was assigned to the hydroxy group of hemiacetal structure and methylene protons of benzyl group, respectively (Figure S3 in Supporting Information). A solution of DPPT in dehydrated CHCl3 exhibited a absorption in the region from 400 to 500 nm with maximum ε at 450 nm due to the carbonyl n−π* transitions (Figure S4 in Supporting Information).9 On the other hand, in the UV−vis spectrum of DPPT−BnOH measured in CHCl3/BnOH (9/1, v/v), there was only a negligible absorption in the same region due to the collapse of the conjugate system consisted of the three sequential carbonyl groups by the formation of hemiacetal structure. These spectroscopic results indicate that the fixation of BnOH to DPPT proceeded smoothly to provide DPPT− BnOH, which has hemiacetal structure. Next we examined the fixation of various alcohols by DPPT by 1H NMR measurements (Figure 1). The reaction rate of 1hexanol, simple primary alcohol, was the fastest and the conversion reached 87% after 7 h (Figure 1b). On the other hand, the reaction rate of 2-hexanol, which is typical secondary alcohol, was much slower than those of 1-hexanol and BnOH, and the conversion was 52% even after 70 h (Figure 1c). 2Methyl-2-pentanol, tertiary alcohol, did not react with DPPT at all (Figure 1d). These results indicate that the bulkiness of alcohols has a great influence on the reaction rate of alcohols with DPPT. Phenol did not also react with DPPT (Figure 1e). This reason is not clear at present. The elimination of phenol may proceed predominantly due to a good leaving ability of phenol. The effect of solvent on the reaction of alcohols with DPPT was also investigated (Figure 2). The fixation of BnOH by DPPT also proceeded in chlorobenzene-d5 (PhCl-d5), which is one of the nonpolar solvents, and the conversion was 40% after 4.5 h. However, unfortunately, we could not estimate the

Scheme 3. Reversible Fixation and Release of Alcohols by 1,3-Diphenylpropanetrione (DPPT)

Figure 1. Time-dependences of conversion of DPPT in the addition of benzyl alcohol (a), 1-hexanol (b), 2-hexanol (c), 2-methyl-2pentanol (d), and phenol (e) in CDCl3 at ambient temperature.

BnOH determined by 1H NMR analyses. The conversion reached a constant value (79%) after 19.5 h. To elucidate the fixation of BnOH to DPPT, we attempted the isolation of DPPT−BnOH (Scheme 4). The reaction of DPPT with Scheme 4. Synthesis of DPPT−BnOH by the Reaction of DPPT and BnOH

Figure 2. Time-dependences of conversion of DPPT in the fixation of benzyl alcohol (A) and 1-hexanol (B) in CDCl3 (a), PhCl-d5 (b), and DMSOd6 (c) at ambient temperature. 4496

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Figure 3. Time-dependences of conversion of DPPT−BnOH in the release of benzyl alcohol from DPPT−BnOH in CDCl3 (a) and DMSO-d6 (b) at ambient temperature (A) and 50 °C (B).

further conversion due to the poor solubility of DPPT−BnOH in PhCl-d5. Therefore, we estimated the reactivity in PhCl-d5 by using 1-hexanol. The reaction rate of 1-hexanol in PhCl-d5 was the same as that in CDCl3. On the other hand, the reaction rate of BnOH and 1-hexanol in DMSO-d6 was much slower than that in CDCl3 and PhCl-d5, indicating that polar solvents such as DMSO hinder the interaction of alcohols with DPPT. For investigating the release behavior of alcohol-adduct of DPPT, the 1H NMR analyses of isolated DPPT−BnOH was performed in dilute solution (0.1 M). In the 1H NMR spectrum, the peak intensity of DPPT−BnOH decreased with time and the peaks derived from DPPT and BnOH appeared, indicating that the reaction of DPPT with alcohol is equilibrium. Figure 3 exhibits the time-dependence of conversion of DPPT−BnOH in the release of BnOH from DPPT−BnOH in CDCl3 and DMSO-d6 at ambient temperature and 50 °C. The release at ambient temperature was rather slow and the conversion did not reached a constant value even after 120 h. On the other hand, the release of BnOH proceeded rapidly at 50 °C and the estimated conversion after 41 h in CDCl3 and 14.5 h in DMSO-d6 was 79 and 93%, respectively. The release rate in DMSO-d6 was much faster than that in CDCl3. These results indicate that DMSO accelerates the release of BnOH from DPPT−BnOH. The equilibrium constant of the reaction of DPPT with BnOH in CDCl3 and DMSO-d6 was estimated to be 3 and 0.8 M−1, respectively.10 The release behavior of BnOH from DPPT−BnOH in a bulk state was also investigated by using thermal gravimetric (TG) analysis (Figure S5 in Supporting Information). TG profile of DPPT showed only a negligible weight loss below 150 °C. On the other hand, a clear weight loss from 120 °C was observed in TG profile of DPPT−BnOH. These results indicate that the release of BnOH from DPPT−BnOH in a bulk state proceeded by heating under nitrogen flow. Reversible Fixation and Release Behavior of Alcohols by 1. Next we investigated the reversible fixation and release behavior of alcohols by 1. On the basis of the results of fixation of alcohols by DPPT, we chose CHCl3 and 1-hexanol as solvent and alcohol for fixation by 1 (Scheme 5). The addition of excess 1-hexanol caused the precipitation of 1 due to the poor solubility of 1 in 1-hexanol, and therefore, 1-hexanol was added in stages (see Experimental Section). As was expected from the high reactivity of DPPT with 1-hexanol, 1 was also readily transformed into its hemiacetal form (1-HexOH). The structure of 1-HexOH was confirmed by IR, 1H NMR, and

Scheme 5. Reversible Fixation and Release of 1-Hexanol (HexOH) by 1

UV−visible. The 1H NMR spectrum of 1-HexOH showed two broad signals at 5.98 and 3.41 ppm, which was assigned to the hydroxy group of hemiacetal structure and methylene protons, respectively (Figure 4B). Although the IR absorption derived from the central carbonyl group of 1 was observed at 1720 cm−1, this absorption disappeared completely and new peak due to hydroxy group of hemiacetal structure appeared at 3392 cm−1 in the IR spectrum of 1-HexOH (Figure 5, parts A and B). The spectrum of a solution of 1 in anhydrous CHCl3 indicated a weak but distinct absorption due to the n−π* transitions of carbonyl groups appeared at around 455 nm. (Figure S6 in Supporting Information).9 On the other hand, in the UV−vis spectrum of 1-HexOH measured in CHCl3/nhexanol (9/1, v/v), there was only a negligible absorption in the same region due to the collapse of the conjugate system consisted of the three sequential carbonyl groups by the formation of hemiacetal structure. These spectroscopic results indicate that the fixation of 1-hexanol to 1 proceeded smoothly to provide 1-HexOH, which has hemiacetal structure. The addition rate of 1-hexanol to 1 estimated based on the 1H NMR spectrum was 85% (Table S1 in Supporting Information). Furthermore, the fixation of ethanol to 1 also proceeded to produce the corresponding ethanol-adduct of 1 (Table S1 in Supporting Information). The release behavior of 1-hexanol from 1-HexOH in a bulk state was investigated by using TG analysis (Figure 6). In the TGA measurements, 1 and 1-HexOH were heated from 30 to 550 °C under nitrogen flow. 1 showed only a negligible weight loss below 150 °C. By elevating temperature, weight loss occurred gradually, and above 300 °C, a significant weight loss presumably due to decomposition of the polymer was observed. On the other hand, upon heating polymer 1-HexOH, a clear 4497

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Figure 6. TG profiles of 1-HexOH (a) and 1 (b).

stage was 25%, which was in good accordance with the weight of 1-hexanol that can be released potentially from 1-HexOH, implying that the release of 1-hexanol from 1-HexOH was successfully conducted in a bulk state. Above 200 °C, a significant weight loss due to the decomposition of the polymer started. Based on TGA results, we performed the release of 1-hexanol from 1-HexOH at 100 °C in vacuo. The 1H NMR and IR spectra of 1 obtained by heating 1-HexOH at 100 °C in vacuo were good agreement with those of original 1 (Figure 4, parts A and C, and Figure 5, parts A and C). These results indicate that the release of 1-hexanol from 1-HexOH by heating proceeded completely, leading to the generation of 1. Reversible Cross-Linking−De-Cross-Linking Behavior of 1 with Diol. Finally, we attempted the application of the reversible fixation and release of alcohols by 1 to synthesis of networked polymer capable of reversible cross-linking-de-crosslinking (Scheme 6): The solution of 1 gelled by the addition of 1,6-hexanediol ([OH]/[tricarbonyl moiety of 1] = 0.1) (Scheme 6B), and the corresponding networked polymer was obtained in high yield (94%) as CHCl3 insoluble part. In the IR spectrum of obtained networked polymer, a weak peak due to hydroxy group of hemiacetal structure was observed at 3404 cm−1 (Figure 7). The obtained networked polymer was insoluble in CHCl3 and DMSO, which are good solvent for 1. These results demonstrate the formation of networked polymer of 1 cross-linked by 1,6-hexanediol through the fixation of alcohol to tricarbonyl moiety. As mentioned above, 1-HexOH could be transformed into 1 by heating in vacuo. On the basis of this result, de-cross-linking of networked polymer was carried out by heating. However, unfortunately, we could not achieve the de-cross-linking of networked polymer by heating, because the temperature to remove 1,6-hexanediol was higher than decomposition one of 1. Therefore, we attempted the de-cross-linking of networked polymer in DMSO containing water (Scheme 6): The networked polymer was dispersed in DMSO/H2O (9/1, v/v) and heated at 50 °C. After 6 h, the reaction mixture became homogeneous (Scheme 6B). The polymer recovered as waterinsoluble part was heated in vacuo at 100 °C for 6 h to gave 1 in 96% yield. The 1H NMR spectrum of obtained 1 was good agreement with those of original 1 (Figure S7 in Supporting Information). These results indicate that the de-cross-linking of networked polymer by heating at 50 °C in DMSO containing water proceeded, leading to the generation of 1

Figure 4. 1H NMR (CD2Cl2) spectra of 1 (A), 1-HexOH (B), and 1 obtained by heating 1-HexOH at 100 °C for 15 h in vacuo. The X denotes solvent residual peak.

Figure 5. IR spectra of 1 (A), 1-HexOH (B), and 1 obtained by heating 1-HexOH at 100 °C for 15 h in vacuo.

weight loss started from about 75 °C until the weight loss reached the plateau at around 165 °C. The weight loss at this 4498

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Scheme 6. (A) Reversible Cross-Linking−De-Cross-Linking Behavior of 1 with 1,6-Hexanediol and (B) Photographs of the Reaction Mixture just after Cross-Linking (a) and De-Cross-Linking (b)

Aid for Scientific Research (B) (21350068) from the Japan Society for the Promotion of Science (JSPS), Japan.

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Figure 7. IR spectrum of networked polymer obtained by the reaction of 1 with 1,6-hexanediol.

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SUMMARY In summary, the reversible fixation and release behavior of alcohols by a polystyrene derivative bearing acyclic vicinal tricarbony moieties (1) and 1,3-diphenylpropanetrione as a model compound of 1 was investigated in detail. Furthermore, we succeeded in the synthesis of a networked polymer capable of reversible cross-linking-de-cross-linking through fixation and release of alcohols by 1. We believe that the insights obtained in this paper may enable functionalization of various polymers and construction of functional networked polymer capable of reversible cross-linking-de-cross-linking. These are now in progress.

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REFERENCES

(1) Rubin, M. B.; Gleiter, R. Chem. Rev. 2000, 100, 1121−1164. (2) Wasserman, H. H.; Parr, J. Acc. Chem. Res. 2004, 37, 687−701. (3) Nair, V.; Deepthi, A. Tetrahedron Lett. 2006, 47, 2037−2039. (4) Adlington, R. M.; Baldwin, J. E.; Catterick, D.; Pritchard, G. J. J. Chem. Soc., Perkin Trans. 1 2000, 299−302. (5) Goswami, S.; Maity, A. C.; Fun, H.; Chantrapromma, S. Eur. J. Org. Chem. 2009, 1417−1426. (6) (a) Dei, T.; Morino, K.; Sudo, A.; Endo, T. J. Polym. Sci. Part A; Polym. Chem. 2011, 49, 2245−2251. (b) Dei, T.; Morino, K.; Sudo, A.; Endo, T. J. Polym. Sci. Part A; Polym. Chem. 2012, 50, No. in press. (7) Endo, T.; Fujiwara, E.; Okawara, M. J. Polym. Sci. Polym. Chem. Ed. 1981, 19, 1091−1099. (8) Wasserman, H. H.; Lee, G. M. Tetrahedron Lett. 1994, 35, 9783− 9786. (9) Rubin, M. B. Chem. Rev. 1975, 75, 177−202. (10) The reversible fixation and release of alcohols with DPPT may be greatly affected by the polarity of solvents (Scheme S1 in the Supporting Information): in CDCl3, alcohol first interacts with DPPT by hydrogen bonding, and then, alcohol adduct of DPPT is formed through the 4-membered intermediate. In DMSO-d6, the hydrogen bonding interaction between alcohol and DPPT is hindered, and therefore, the addition rate becomes slower than that in CDCl3. On the other hand, the hydroxy group of alcohol-adduct of DPPT is activated by the hydrogen bonding with DMSO-d6, resulting in the acceleration of elimination of alcohol from alcohol-adduct of DPPT.

ASSOCIATED CONTENT

S Supporting Information *

1

H NMR, IR, and UV−vis spectra and TG profiles of DPPT and DPPT-BnOH, possible mechanism of reversible fixation and release of alcohols by DPPT, UV−vis spectra of 1 and 1HexOH, results of addition of 1-hexanol and ethanol to 1, and 1 H NMR spectra of 1 obtained from networked polymer. This material is available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Telephone and Fax: +81-948-22-7210. E-mail: tendo@ moleng.fuk.kindai.ac.jp. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank Dr. Y. Furusho and Mr. M. Yonekawa for their experimental assistance. This work was supported by Grant-in4499

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