Unusually Lowered Acidity of Ammonium Group Surrounded by Crown Ether in a Rotaxane System and Its Acylative Neutralization

Kihara, Nobuhiro; Tachibana, Yuya; Kawasaki, Hiroaki; Takata, Toshikazu

doi:10.1246/cl.2000.506

Cited by 96 publications

(98 citation statements)

References 11 publications

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“…30,34 Polymer 7 Ac obtained in 96% yield after 24 h reaction was a red-colored solid, similar to 8. The SEC molecular weight of 7 Ac reached M n 465Â10 3 (M w /M n 5.9), being sufficiently high as a polyhenylacetylene.…”

Section: Monomer Synthesismentioning

confidence: 86%

“…As these spectra were well coincident each other in the fingerprint region and no decomposition product was confirmed through purification, the obtained polymer must retain the rotaxane structure after polymerization under basic conditions, as described in previous reports. 30,34 Otherwise, the amide carbonyl absorption around 1700 cm -1 of 6 (N-Ac) was not lost in 8 (Figures 2c and d). Most reliable evidence was found in the UV-vis spectra of 7 and 8, which showed clear absorption peaks at the 450-500 nm region characteristic of the absorptions based on conjugated polyphenylacetylene main chains (Figure 4).…”

Section: Monomer Synthesismentioning

confidence: 93%

“…33 Pseudorotaxane 2 was prepared in situ from DB24C8 and hydroxy-terminated sec-ammonium salt 1 in chloroform. To a solution of 2 were added 3, N,N¢-dicyclohexylcarbodiimide and a catalytic amount of tributylphosphane, 30,34 and the mixture was stirred for 1 h at room temperature. Purification by preparative highperformance liquid chromatography resulted in ethynyl-protected rotaxane 4 in 54% yield.…”

Section: Monomer Synthesismentioning

confidence: 99%

“…Splitting of the crown ether oxyethylene proton signals were characteristic of this type of rotaxane, as assigned in Figure 1. 30,[35][36][37] O-Benzylic proton signal, which is sensitive to the position of the crown ether wheel on the axle, moved to 5.9 p.p.m., indicating the localization of the wheel around the ester group. This result suggests that the wheel component gets considerably close to the acetylene moiety in comparison with that of 5.…”

Section: Monomer Synthesismentioning

confidence: 99%

“…30 Considering the increasing bulkiness by the movement of the crown ether wheel in the conversion of 7 to 7 Ac , the polymerizability of 6 can be estimated to be somewhat low as a result of the increased steric hindrance around the acetylene group, but it was very high if SEC data are reliable (Table 1). Rotaxane-tethering acetylene monomers and side chain-type polyrotaxanes K Nakazono et al…”

Section: Monomer Synthesismentioning

confidence: 99%

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Synthesis of acetylene-functionalized [2]rotaxane monomers directed toward side chain-type polyrotaxanes

Nakazono

Fukasawa

Sato

et al. 2010

Polym J

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A crown ether-ammonium salt-type rotaxane monomer was synthesized in a high yield using dibenzo-24-crown-8-ether and sec-ammonium salt having a hydroxy terminal by means of an end-capping reaction with an ethynyl benzoic acid. Its N-acetylated derivative was also synthesized in a quantitative yield using excess acetic anhydride and triethylamine. Novel side chain-type polyrotaxanes, that is, ammonium-type and neutral polyphenylacetylenes tethering rotaxane moieties in side chains with high molecular weights, were obtained in high yields by polymerizations with an Rh catalyst. The structures of the polymers were characterized by infrared, ultraviolet-visible (UV-vis) spectra and size exclusion chromatography. N-acetylation of the rotaxane moieties of the ammonium salt-type polymer resulted in the formation of a reddish-colored neutral polymer showing red-shifted UV-vis absorptions around 500 nm based on the conjugated main chain, according to the structural change of rotaxane side chains, that is, the change of the distance of the wheel component to the polyacetylene main chain. The solubility of the polymers was evaluated.

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Section: Monomer Synthesismentioning

confidence: 86%

Section: Monomer Synthesismentioning

confidence: 93%

Section: Monomer Synthesismentioning

confidence: 99%

Section: Monomer Synthesismentioning

confidence: 99%

Section: Monomer Synthesismentioning

confidence: 99%

See 3 more Smart Citations

Synthesis of acetylene-functionalized [2]rotaxane monomers directed toward side chain-type polyrotaxanes

Nakazono

Fukasawa

Sato

et al. 2010

Polym J

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Template-Directed Synthesis of a [2]Rotaxane by the Clipping under Thermodynamic Control of a Crown Ether Like Macrocycle Around a Dialkylammonium Ion

et al. 2001

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New synthetic procedures for preparing rotaxanes [1] are appearing in the current literature [2] with ever-increasing regularity as a result of the attention [3] these mechanically interlocked molecules [4] are receiving because of their rapidly growing promise as molecular switches for developing devices [5] on the mesoscale and as linear motor-molecules for constructing artificial molecular machinery [6] on the nanoscale. One of the simplest recognition motifs that produces pseudorotaxanes, [7] complexes that are often the precursors of catenanes and rotaxanes, is the binding [8] of dialkylammonium ions with suitably large macrocycles, for example, dibenzo[24]crown-8. Although this motif has so far yielded rotaxanes by both the threading-followed-by-stoppering [9] and slippage [10] approaches, until now no rotaxanes based on the dialkylammonium ion have been synthesized using a clipping [11] protocol. Here, we report the template-directed synthesis [4c, 12] of a [2]rotaxane by a clipping approach under thermodynamic control and the subsequent conversion of the dynamic products into a kinetically stable [2]rotaxane which species thus provide unequivocal evidence that the delocalization of the p electrons is responsible for the C 2v cyclic structure, rendering the more metallic heterosystems aromatic. Schaefer and co-workers [16] recently performed theoretical studies on model heterocyclic three-membered ring systems related to the Ga 3 organometallic compounds and concluded that these systems were indeed also aromatic.Herein we extended the concept of aromaticity to the heterocyclic four-membered ring all-metal systems, XAl 3 À . We showed systematically the importance of the delocalization of the p electrons for the stability of the cyclic aromatic structure. Metallic systems can be aromatic when they are composed of heteroatoms, provided that the heteroatoms have similar electronegativities to the rest of atoms of the ring. However, if the heretoatoms differ substantially in their electronegativities, such as C in CAl 3 À , [14] the cyclic aromatic structure is no longer a minimum. [12] We initially optimized the geometries and calculated the frequencies of XAl 3 À by using analytical gradients with polarized split-valence basis sets (6-311 G*) for Al, Si and Ge in XAl 3 À , and the LANL2DZ basis sets (extending by additional two s, two p and one d functions resulting in (5s5p1d/4s4p1d) basis sets) and the relativistic effective core potentials for Al, Sn, and Pb in XAl 3 À , and a hybrid method known in the literature as B3LYP. Then we refined the geometries and calculated the frequencies at the second-order Mùller-Plesset perturbation theory (MP2) level. The two most stable planar cyclic and pyramidal structures were studied further by using the coupled-cluster method (CCSD(T)) with the same basis sets. The energies of the most stable structures were refined by using the CCSD(T) method, the more extended 6-311 G(2df) basis sets for Al, Si, and Ge, and (5s5p2d1f/4s4p2d1f) valent basis sets and relativi...

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Post-Assembly Processing of [2]Rotaxanes

et al. 2002

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Recognize this! A hydrogen‐bonding motif based on hexafluorinated alcohol derivatives (see picture; O red, F yellow) activates electrophilic substrates. The catalytic activity of the hydrogen‐bonded systems was demonstrated for the ring‐opening polymerization of a variety of strained heterocycles. Narrowly dispersed polymers with predictable molecular weights were obtained with end‐group fidelity.

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Unusually Lowered Acidity of Ammonium Group Surrounded by Crown Ether in a Rotaxane System and Its Acylative Neutralization

Abstract: Acidity of a secondary ammonium group in a rotaxane system with a crown ether was unusually lowered. N-Acylation of the ammonium group by acid anhydrides or chlorides proceeded slowly in the presence of excess tertiary amine to give the N-acylated rotaxanes without salt structure.

Cited by 96 publications

References 11 publications

Synthesis of acetylene-functionalized [2]rotaxane monomers directed toward side chain-type polyrotaxanes

Synthesis of acetylene-functionalized [2]rotaxane monomers directed toward side chain-type polyrotaxanes

Template-Directed Synthesis of a [2]Rotaxane by the Clipping under Thermodynamic Control of a Crown Ether Like Macrocycle Around a Dialkylammonium Ion

Post-Assembly Processing of [2]Rotaxanes

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