Abstract
Application of a dynamic covalent chemistry strategy to the reversible reaction system of resorcinol and α, ω-alkanedials [(CH2)m(CHO)2] (m = 2–10) in ethanol in the presence of hydrogen chloride (HCl) solution as a catalyst at 80 °C for 48 h afforded the thermodynamically most stable products with high selectivity. The reaction of 1,4-butanedial afforded a ladder polymer containing calixarene skeletons in the main chain in quantitative yield. 1,5-Pentanedial gave Noria, a water-wheel-like cyclic oligomer, in high yield. Calixarene-dimer-type cyclic oligomers were formed selectively from 1,6-hexanedial, 1,8-octanedial, 1,10-decanedial, and 1,12-dodecanedial, while calixarene-trimer-type cyclic oligomers were obtained selectively from 1,7-heptanedial, 1,9-nonanedial, and 1,11-undecanedial. The Noria like macrocyles NoriaPY NoriaMP and NoriaEP could be also synthesized via DCC using pyrogallol, 3-methoxyphenol, and 3-ethoxyphenol. A triple-ringed[14]arene could be synthesized via DCC using the reaction of 2-methylresorcinol and m-benzenedicarbaldehyde.
Introduction
In dynamic covalent chemistry (DCC), reversible chemical reactions proceed under thermodynamic control, enabling the most stable compound to be synthesized by a one-pot procedure as a result of “error checking” and “proof-reading” processes during the reaction.1–7 This approach has been widely applied, for example, to olefin metathesis reactions, condensation reactions of amine and aldehyde, cleavage reactions of disulfide, transesterification, and transacetalization. Two-dimensional cyclic oligomers have been synthesized using alkynes,8–10 alkenes,11–13 disufides,14,15 and imines,16,17 and three-dimensional cage compounds have been obtained from imines,18–23 disulfides,24 and boronate esters.25–28 These macrocycles have high thermal stability, and have various potential applications as functional materials. Cyclic oligomers synthesized with DCC systems include calixarenes, which have hydrophobic fixed holes through their center and many hydroxyl groups in the side chain; these compounds can form inclusion complexes with some metal ions, and are of interest in the field of host-guest chemistry.29–32 However, synthetic strategies for calixarenes remained essentially unchanged for about 50 years, until Gutsche et al. showed that calixarenes could be synthesized in high yield by the addition condensation reaction of phenols and aldehydes under thermodynamic control in a DCC system under appropriate reaction conditions (Scheme 1).33,34
Reaction of resorcinol and aldehydes.
The authors have examined similar reactions for the synthesis of calixarenes using phenols and dialdehydes and achieved the synthesis of various unique cyclic oligomers based on DCC.
This highlight review focuses on DCC systems comprising the addition condensation reaction of phenols and dialdehydes.
Reaction of Resorcinol and 1,5-Pentanedial [(CH2)m(CHO)2] (m = 3)
Calixarenes are synthesized by the addition condensation reaction of phenols and aldehydes as difunctional monomers, i.e., A2 + B2 type step-growth polymerization proceeds to give two-dimensional macrocycles in satisfactory yields in a DCC system as shown in Scheme 1. The reactions of resorcinol as a difunctional monomer with 1,5-pentanedial [(CH2)3(CHO)2] as tetrafunctional monomers were examined, i.e., A2 + B4 type step-growth polymerization. Generally, cross-linked materials and hyperbranched polymers would be synthesized in this type of polymerization, and it was expected that a small amount of calixarene-dimer might be obtained as a by-product as shown in Scheme 2.
Reaction of resorcinol and 1,5-pentanedial.
Initially, we thought that a cross-linked material would be obtained as a main product at an equivalent ratio of functional groups (resorcinol/1,5-pentandiol = 2/1) at 80 °C for 48 h. However, only soluble product could be obtained. Then the reaction temperature effect of this A2 + B4 addition condensation reaction was investigated. Figure 1 shows the effect of reaction temperature on the addition condensation reaction of resorcinol and 1,5-pentanedial at the feed of resorcinol/1,5-pentanedial = 2/1 for 48 h in the range between 0 and 80 °C.
Effect of reaction temperature on the addition condensation reaction of resorcinol and 1,5-pentanedial at the feed of resorcinol/1,5-pentanedial = 2/1 for 48 h. ■; Cross-linked materials, ●; soluble low-molecular-weight compound (Noria).
Only cross-linked products could be obtained at reaction temperatures below 40 °C, but the amount of cross-linked products decreased as the reaction temperature was increased, and only a soluble product was obtained in 20% yield at 80 °C. 1H NMR, 13C NMR, IR, and MALDI-TOF mass spectroscopic examination of the soluble product, as well as single X-ray analysis and elemental analysis of a derivative of the soluble product, revealed that it was the ladder-cyclic oligomer Noria (Figure 2).35
Top and side view of Noria.
Noria means water wheel in Latin, and has 24 hydroxyl groups, 6 cavities in the side, and a large hydrophobic hole through the center, as shown in Scheme 2. Noria is soluble in aprotic highly polar solvents, such as dimethylformamide (DMF), dimethylsulfoxide (DMSO), dimethylacetamide (DMAc), and 1-methyl-2-pyrrolidinone (NMP), and has high thermal stability (Tdi = 333 °C).
When the effect of 1,5-pentanedial/resorcinol feed ratios in the range of 1/20–10/20 on this addition condensation at 80 °C for 48 h was examined, Noria was obtained as the sole product in a yield ranging from 18 to 83%. The results are summarized in Figure 3. Finally, the use of 1,5-pentanedial/resorcinol = 5/20 (1/4) at 80 °C for 48 h afforded the highest yield of Noria (83%), with no formation of cross-linked product.
Yields of Noria at 1,5-pentanedial/resorcinol feed ratios of 1/20–10/20 at 80 °C for 48 h.
These results indicate that Noria was formed under thermodynamic control, i.e., it is the most stable compound, and therefore is formed selectively in this DCC system. Specifically, poly(Re-co-Pe) with Mn = 4,200 and Mw/Mn = 1.46 could be obtained at the feed ratio of 1,5-pentanedial/resorcinol = 1/2 at 40 °C for 1 h (Scheme 3). Its composition ratio was determined by 1H NMR spectroscopy to be resorcinol/1,5-pentanedial = 1/2.4 (Figure 4).
Synthesis of poly(Re-co-Pe) by the addition condensation reaction of resorcinol and 1,5-pentanedial in the feed ratio of resorcinol/1,5-pentanedial = 1/2.
1H NMR spectrum of poly(Re-co-Pe) (Mn = 4,200, Mw/Mn = 1.46).
The solubility and thermal stability of the synthesized poly(Re-co-Pe) were quite different from those of Noria. The synthesized poly(Re-co-Pe) was soluble in water and common organic solvents such as CHCl3, THF, acetone, and ethanol. Poly(Re-co-Pe) had lower thermal stability than Noria (Figure 5), i.e., poly(Re-co-Pe) serves as a precursor of Noria. To confirm this, we prepared a solution of poly(Re-co-Pe) and resorcinol in ethanol in the presence of hydrogen chloride (HCl) solution as a catalyst, and stirred the mixture for 48 h. Figure 6 depicts the SEC profiles of the obtained products with increasing reaction time. After 5 min, peaks of polymer, Noria, and oligomer were observed at the retention times of 30 min, 32 min, and 35 min, respectively. We observed a decrease in the amount of polymer and an increase in that of Noria as the reaction progressed. After 6 and 48 h, only Noria and oligomer were observed, and poly(Re-co-Pe) was not detected. These results support the idea that the reaction of resorcinol/1,5-pentanedial proceeds under DCC conditions to give Noria selectively under thermodynamic control.
TGA curves of poly(Re-co-PE) (Mn = 4,200, Mw/Mn = 1.46) and Noria.
SEC profiles of the products obtained by the reaction of poly(Re-co-Te) and resorcinol in the presence of HCl solution in ethanol at 80 °C.
Furthermore, the oligomer with the retention time of 35 min might be a key compound leading to Noria. Therefore, it was separated by silica gel column chromatography, and its structure was confirmed by 1H NMR spectroscopy to be 1,1,5,5-tetra(2,4-dihydroxyphenyl)pentane (TDPP), which would be formed by the condensation reaction of 4 equivalents of resorcinol with 1,5-pentanedial. When TDPP was heated in ethanol in the presence of conc. HCl solution at 80 °C for 48 h, Noria was obtained in quantitative yield, accompanied with the formation of resorcinol. These results suggest that TDPP was formed by a reversible reaction between polymer, resorcinol, and 1,5-pentanedial, followed by the elimination reaction of resorcinol with TDPP in this DCC system. The synthesized TDPP produced Noria selectively, which is consistent with the observation that Noria was obtained in the highest yield at the feed molar ratio of 1,5-pentanedial/resorcinol = 1/4 (0.25), as shown in Figure 2. These results indicate that reaction of resorcinol and 1,5-pentanedial for the synthesis of Noria follows a DCC mechanism as illustrated in Scheme 4.
Mechanism of formation of Noria from resorcinol and 1,5-pentanedial.
The reaction of resorcinol and 1,5-pentanedial affords poly(Re-co-Te) in the first step, and then a part of poly(Re-co-Te) is decomposed to give TDPP, which yields the most thermodynamically stable compound Noria in this reversible reaction system.
Reaction of Resorcinol and α,ω-Alkanedials [(CH2)m(CHO)2] (m = 2 and 4–10)
The reaction of resorcinol and other α,ω-alkanedials [(CH2)m(CHO)2] (m = 2 and 4–10) was examined under the conditions used for the synthesis of Noria. In the case of 1,4-butanedial [(CH2)m(CHO)2] (m = 2), no cross-linked product or macrocyclic compound was obtained, and only soluble polymer with Mn = 11,400, Mw/Mn = 2.51 was formed in quantitative yield. 1H NMR, 13C NMR, IR, MALDI-TOF mass spectroscopic examination and single-crystal X-ray analysis of a model compound showed that the obtained polymer contained alternating calix[4]resorcinarene (CRA) structures in the main chain, i.e., a new class of ladder polymer (CRA-polymer) was synthesized selectively, as shown in Scheme 5.36
Reaction of resorcinol and 1,4-butanedial.
In the case of 1,6-hexanedial [(CH2)m(CHO)2] (m = 4), only soluble oligomer was obtained, and its structure was also examined by 1H NMR, 13C NMR, IR, MALDI-TOF mass spectroscopy, and single-crystal X-ray analysis.37,38 This oligomer had two calix[4]resorcinarene (CRA) skeletons up and down both sides and the CRAs were connected by four chains containing four methylenes derived from 1,6-hexanedial; this oligomer was named calixiarene-dimer[4] (Scheme 6).
![Reaction of resorcinol and α, ω-alkanedial [OHC-(CH2)m-CHO, m = 4, 6, 8, and 10].](https://oup.silverchair-cdn.com/oup/backfile/Content_public/Journal/chemlett/50/4/10.1246_cl.200773/5/m_cl-200773sc06.jpeg?Expires=1747877261&Signature=c02Cws1pN~5kPoYgtdiI1OIZeDCDrGomq2n~LSiV~~EXM7RnkJtMjhj6JFpohFe1yVV7dcV4YPWjHGvovmrise3pSxPSikpCqaJDTNq3U1WOoSEiDGX0dWbeM~0HbFSQ0~9m7Hcc0bi9Qy7mTAoovc93kLEwZmrQ8llzJ1arjPAK2QyGcipRRPfAKzo3y79DPWMHMtoL3Pbz3c12LyTjExaFNDDhfNE607kgVRM1nUA5xLEe0YvtV9GM-U4UBXoxgT5ufiJFQI9oWZKkmOV~-GF5fjmppiagClWDRPppBlGUekKPR09VYe4-AjFGbl5NadDfpR59KYgHwVRz7iMLQw__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Reaction of resorcinol and α, ω-alkanedial [OHC-(CH2)m-CHO, m = 4, 6, 8, and 10].
The reaction of resorcinol and 1,7-heptanedial [(CH2)m(CHO)2] (m = 5) afforded only soluble oligomer containing three calix[4]resorcinarene (CRA) structures, in which the CRAs were connected by six chains of five methylenes derived from 1,7-heptanedial.39 This oligomer was named calixiarene-trimer[5] (Scheme 7).
![Reaction of resorcinol and α, ω-alkanedial [OHC-(CH2)m-CHO, m = 5, 7, and 9].](https://oup.silverchair-cdn.com/oup/backfile/Content_public/Journal/chemlett/50/4/10.1246_cl.200773/5/m_cl-200773sc07.jpeg?Expires=1747877261&Signature=hPhOItWqkaAaP3jE8~QKJ9noVxOUTSFRXQXkQHNAP75ZnvVcYtTuyHeT2O7iRwuz3~V9nuwLpmTU7EU0ELomP4JA2Xl7E4CxFujcNL1CDn8-WTrFh6A6QAcaaIWG~2OidT6XH1-N-KOojrmCnXmbZh8JejOWoTqL5yMkrKlhbG6ICpfLsNqGnYzNtXNb4LwWD1TLC3uEF~tVF3R61vlC308F~pcc2MUn8B0b8zagS-IVWfbfaGD1Isxi0HpqB4If8LgMzTS6sl5nQ~LqYPRgqaC96YBYnhRkt2TdbhyH~5S7sgd5FPZerxym6PL3nYd1HOI3OmA8HZBIB5dSreNCrA__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Reaction of resorcinol and α, ω-alkanedial [OHC-(CH2)m-CHO, m = 5, 7, and 9].
Further examination of other α,ω-alkanedials [(CH2)m(CHO)2] showed that those with even-numbered values of m afforded the corresponding calixarene-dimer[m] (m = 6, 8, and 10), while those with odd-numbered values of m afforded the corresponding calixarene-trimer[m] (m = 5, 7, and 9) and their structures were also confirmed by 1H NMR, 13C NMR, IR, MALDI-TOF mass spectroscopy, and single-crystal X-ray analysis. These results are summarized in Table 1.
Addition condensation reaction of resorcinol and α,ω-alkanediala
| Run | α,ω-alkanedial | Yield (%) | ||
|---|---|---|---|---|
| Dimer | Trimer | Polymer | ||
| 1 | 1,4-Butanedial | 0 | 0 | 99b |
| 2 | 1,5-Pentanedial | 0 | 83c | 0 |
| 3 | 1,6-Hexanedial | 26d | 0 | 0 |
| 4 | 1,7-Heptanedial | 0 | 18d | 0 |
| 5 | 1,8-Octanedial | 21d | 0 | 0 |
| 6 | 1,9-Nonanedial | 0 | 16d | 0 |
| 7 | 1,10-Decanedial | 23d | 0 | 0 |
| 8 | 1,11-Undecanedial | 0 | 15d | 0 |
| 9 | 1,12-Dodecanedial | 22d | 0 | 0 |
| Run | α,ω-alkanedial | Yield (%) | ||
|---|---|---|---|---|
| Dimer | Trimer | Polymer | ||
| 1 | 1,4-Butanedial | 0 | 0 | 99b |
| 2 | 1,5-Pentanedial | 0 | 83c | 0 |
| 3 | 1,6-Hexanedial | 26d | 0 | 0 |
| 4 | 1,7-Heptanedial | 0 | 18d | 0 |
| 5 | 1,8-Octanedial | 21d | 0 | 0 |
| 6 | 1,9-Nonanedial | 0 | 16d | 0 |
| 7 | 1,10-Decanedial | 23d | 0 | 0 |
| 8 | 1,11-Undecanedial | 0 | 15d | 0 |
| 9 | 1,12-Dodecanedial | 22d | 0 | 0 |
aThe reaction of resorcinol (20 mmol) with α, ω-alkanedial (5 mmol) was carried out in the presence of conc.HCl solution (1.5 mL) in ethanol (4.5 mL) for 48 h. bMn = 5,700, Mw/Mn = 2.91, estimated by SEC (DMF) based on polystyrene standards. cNoria was obtained in 83% yield. dMethanol-insoluble part.
Addition condensation reaction of resorcinol and α,ω-alkanediala
| Run | α,ω-alkanedial | Yield (%) | ||
|---|---|---|---|---|
| Dimer | Trimer | Polymer | ||
| 1 | 1,4-Butanedial | 0 | 0 | 99b |
| 2 | 1,5-Pentanedial | 0 | 83c | 0 |
| 3 | 1,6-Hexanedial | 26d | 0 | 0 |
| 4 | 1,7-Heptanedial | 0 | 18d | 0 |
| 5 | 1,8-Octanedial | 21d | 0 | 0 |
| 6 | 1,9-Nonanedial | 0 | 16d | 0 |
| 7 | 1,10-Decanedial | 23d | 0 | 0 |
| 8 | 1,11-Undecanedial | 0 | 15d | 0 |
| 9 | 1,12-Dodecanedial | 22d | 0 | 0 |
| Run | α,ω-alkanedial | Yield (%) | ||
|---|---|---|---|---|
| Dimer | Trimer | Polymer | ||
| 1 | 1,4-Butanedial | 0 | 0 | 99b |
| 2 | 1,5-Pentanedial | 0 | 83c | 0 |
| 3 | 1,6-Hexanedial | 26d | 0 | 0 |
| 4 | 1,7-Heptanedial | 0 | 18d | 0 |
| 5 | 1,8-Octanedial | 21d | 0 | 0 |
| 6 | 1,9-Nonanedial | 0 | 16d | 0 |
| 7 | 1,10-Decanedial | 23d | 0 | 0 |
| 8 | 1,11-Undecanedial | 0 | 15d | 0 |
| 9 | 1,12-Dodecanedial | 22d | 0 | 0 |
aThe reaction of resorcinol (20 mmol) with α, ω-alkanedial (5 mmol) was carried out in the presence of conc.HCl solution (1.5 mL) in ethanol (4.5 mL) for 48 h. bMn = 5,700, Mw/Mn = 2.91, estimated by SEC (DMF) based on polystyrene standards. cNoria was obtained in 83% yield. dMethanol-insoluble part.
When bisaldehydes containing long-chain alkyl group were used, the yields of the obtained compounds tended to decrease. This might be because the bisaldehydes having a long-chain alkyl group are unstable and their portion might be decomposed during the reaction.
Next, the thermal properties of the synthesized CRA-polymer, Noria, calixarene-dimer[m], and calixarene-trimer[m] were examined. No apparent melting points or Tg's were observed. The thermal decomposition temperatures were all higher than 300 °C. However, when the hydroxyl groups of Noria, calixarene-dimer[m] and calixarene-trimer[m] were converted to ester groups by reaction with ethyl bromoacetate, the corresponding compounds Noria-EE, calixarene-dimer[m]-EE, and calixarene-trimer[m]-EE showed clear melting points in the range between 148.3 and 298.7 °C (Table 2). The relationship between the melting point temperature and the methylene chain length of these derivatives is depicted in Figure 7.
Relationship between melting point temperature and number of methylene chains of α, ω-alkanedials.
Yields and melting points of cyclic oligomer derivatives (Noria-EE, calixarene-dimer[n]-EE, and calixarene-trimer[n]-EE)
| Cyclic oligomers | Yield (%) | M.P. (°C)a |
|---|---|---|
| Noria-EE | 21 | 298.5–298.7 |
| Calixarene-dimer[4]-EE | 75 | 160.2–160.4 |
| Calixarene-trimer[5]-EE | 81 | 255.2–255.4 |
| Calixarene-dimer[6]-EE | 88 | 156.7–156.9 |
| Calixarene-trimer[7]-EE | 88 | 217.8–218.0 |
| Calixarene-dimer[8]-EE | 90 | 151.8–152.0 |
| Calixarene-trimer[9]-EE | 87 | 196.5–196.8 |
| Calixarene-dimer[10]-EE | 90 | 148.3–148.5 |
| Cyclic oligomers | Yield (%) | M.P. (°C)a |
|---|---|---|
| Noria-EE | 21 | 298.5–298.7 |
| Calixarene-dimer[4]-EE | 75 | 160.2–160.4 |
| Calixarene-trimer[5]-EE | 81 | 255.2–255.4 |
| Calixarene-dimer[6]-EE | 88 | 156.7–156.9 |
| Calixarene-trimer[7]-EE | 88 | 217.8–218.0 |
| Calixarene-dimer[8]-EE | 90 | 151.8–152.0 |
| Calixarene-trimer[9]-EE | 87 | 196.5–196.8 |
| Calixarene-dimer[10]-EE | 90 | 148.3–148.5 |
aM.P = melting point temperature.
Yields and melting points of cyclic oligomer derivatives (Noria-EE, calixarene-dimer[n]-EE, and calixarene-trimer[n]-EE)
| Cyclic oligomers | Yield (%) | M.P. (°C)a |
|---|---|---|
| Noria-EE | 21 | 298.5–298.7 |
| Calixarene-dimer[4]-EE | 75 | 160.2–160.4 |
| Calixarene-trimer[5]-EE | 81 | 255.2–255.4 |
| Calixarene-dimer[6]-EE | 88 | 156.7–156.9 |
| Calixarene-trimer[7]-EE | 88 | 217.8–218.0 |
| Calixarene-dimer[8]-EE | 90 | 151.8–152.0 |
| Calixarene-trimer[9]-EE | 87 | 196.5–196.8 |
| Calixarene-dimer[10]-EE | 90 | 148.3–148.5 |
| Cyclic oligomers | Yield (%) | M.P. (°C)a |
|---|---|---|
| Noria-EE | 21 | 298.5–298.7 |
| Calixarene-dimer[4]-EE | 75 | 160.2–160.4 |
| Calixarene-trimer[5]-EE | 81 | 255.2–255.4 |
| Calixarene-dimer[6]-EE | 88 | 156.7–156.9 |
| Calixarene-trimer[7]-EE | 88 | 217.8–218.0 |
| Calixarene-dimer[8]-EE | 90 | 151.8–152.0 |
| Calixarene-trimer[9]-EE | 87 | 196.5–196.8 |
| Calixarene-dimer[10]-EE | 90 | 148.3–148.5 |
aM.P = melting point temperature.
Noria and calixarene-trimer[m] (m = 5, 7, and 9) showed a dramatic decrease of melting point temperature with increasing methylene chain length. On the other hand, calixarene-dimer[m] (m = 4, 6, 8, and 10) containing even numbers of methylene units showed only a slight decrease of melting point temperature with increase of methylene chain length. That is, an even-odd effect was observed in the values of the length of the methylene chain and the melting point of the synthesized cyclic oligomers.
Reaction of Various Phenols and 1,5-Pentanedial
The addition condensation reaction of various phenols and 1,5-pentanedial was also examined. In the case of pyrogallol, a Noria like macrocyle could be synthesized in high yield under the conditions used for the synthesis of Noria (Scheme 8).40
Reaction of pyrogallol and 1,5-pentanedial.
Furthermore, the addition-condensation reaction of 3-alkoxyphenol and 1,5-pentanedial was also examined under the same conditions as mentioned above. As a result, a Noria-like macrocycle could not be obtained, i.e., DCC could not be performed in these reaction conditions. By the examination of reaction conditions using combination of acid catalysts and solvents, the DCC system could be established using trifluoroacetic acid (TFA) as a catalyst in CHCl3 at reflux for 48 h, yielding the targeted Noria-like macrocycles NoriaMP and NoriaEP (Scheme 9).41
Reaction of 3-alkoxyphenol and 1,5-pentanedial.
In the case of p-cresol and p-t-butylphenol, the various reaction conditions have been also examined, but a method for synthesis of selective macrocycle compounds by the DCC system has not yet been found.
Reaction of Various Phenols and m-Benzenedicarbaldehyde
Condensation reaction of various phenols such as 2-methylresorcinol, resorcinol, p-cresol, and p-t-butylphenol with m-benzenedicarbaldehyde was examined. A DCC system could be established using the reaction of 2-methylresorcinol and m-benzenedicarbaldehyde in the presence of HCl solution as a catalyst in n-propanol at 90 °C for 48 h, yielding a triple-ringed[14]arene (Scheme 10).42
Reaction of 2-methylresorcinol and m-benzenecarbaldehyde.
Summary
The addition condensation reactions of resorcinol and α,ω-alkanedials [(CH2)m(CHO)2] (m = 2–10) were examined in ethanol at 80 °C for 48 h in one pot, using a dynamic covalent chemistry (DCC) strategy. The reaction with 1,4-butanedial afforded a soluble ladder polymer containing calixarene skeletons in the main chain in quantitative yield. Noria was obtained from the reaction of 1,5-pentanedial. Calixarene-dimer-type oligomers were obtained from α,ω-alkanedials [(CH2)m(CHO)2] (m = 4, 6, 8, 10) having even numbers of methylene carbons, while calixarene-trimer-type oligomers were obtained from α,ω-alkanedials [(CH2)m(CHO)2] (m = 5, 7, 9) having odd numbers of methylene carbons. The Noria like macrocyles NoriaPY NoriaMP and NoriaEP could be also synthesized via a DCC system. Furthermore, a DCC system could be established using the reaction of 2-methylresorcinol and m-benzenedicarbaldehyde to give a triple-ringed[14]arene. These addition condensation reaction are A2 + B4 type step-growth polymerization, i.e., phenols as a difunctional monomers and dialdehydes as tetrafunctional monomers. When a DCC system could be applied in appropriate reaction conditions, the feed ratio of these monomers needed to be 1:4. This means that the corresponding cyclic compounds could be obtained via an intermediate of 4 equivalents of phenols and 1 equivalent of aldehyde. These DCC systems offer convenient access to various types of fixed-hole-containing polymer and cyclic oligomers, which are expected to find application as novel functional materials.
References and Notes
Hiroto Kudo received a Doctorate in polymer chemistry from Tokyo Institute of Technology, Japan in 2000. He did postdoctoral research at the Venture Business Laboratory at Yamagata University, Japan during 2000–2001. In his career at Kanagawa University, he has progressed from Research Associate (2001) to Assistant Professor (2007), and Associate Professor (2009). In 2013, he moved to Kansai University as an Associate Professor and was promoted to Professor in 2015. His current research interests include synthesis of new functional polymers applicable to EUV resists, UV-curing materials, high and low-refractive indices materials.
Daisuke Shimoyama received his BSc in 2015 and his Ph.D. degree in 2020 from Hiroshima University, where he worked as a JSPS young researcher in the group of Professor Takeharu Haino. After the graduation, he worked as a Ph.D. Researcher in the Graduate School of Advanced Science and Engineering, Hiroshima University. He is currently a postdoctoral associate at Rutgers University in the group of Professor Frieder Jäkle.
Ryo Sekiya graduated from Sophia University in 1998 and received his Ph. D. degree from the University of Tokyo in 2003. He moved to Chiba University as a JSPS young researcher. In 2004, he was appointed as an Assistant Professor to the Graduate School of Arts and Sciences at the University of Tokyo. In 2012, he joined the group of Professor Takeharu Haino at Hiroshima University as an Associate Professor. In 2016, he joined the group of Pablo Ballester at Institut Català d’Investigació Química in Spain. His research interests are in supramolecular chemistry, solid state organic chemistry, and graphenes.
Takeharu Haino received his PhD in 1992 from Hiroshima University. He worked at Sagami Chemical Research Center. He was appointed as an Assistant Professor at Hiroshima University in 1993. He joined the group of Prof. Julius Rebek Jr. as a visiting researcher at The Scripps Research Institute (1999–2000). He became an Associate Professor of Chemistry at Hiroshima University in 2000. He has been a Full Professor since 2007. His research interests encompass the development of functional supramolecular polymer materials and graphene-based functional materials.
