Density functional study of the lithiation of cyclic vinyl ethers in solution

Yan, Zhiqing; Sebastian, John F.

doi:10.1016/j.tet.2004.09.035

Cited by 16 publications

(12 citation statements)

References 12 publications

(15 reference statements)

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“…The transition of the curves was observed at a neutral pH in the absence of d -fructose and at a slightly acidic pH in the presence of 50 mM d -fructose. This is due to the fact that the p K a of the DTBA-PBA− d -fructose conjugate is smaller than that of the unconjugated DTBA-PBA, which is in line with the general trend for p K a values determined in solution; p K a values of sugar esters of phenylboronic acid are often more acidic than that of phenylboronic acid itself . The MPBA monolayer-modified electrode exhibited a similar behavior (Figure B).…”

Section: Resultssupporting

confidence: 74%

“…For improving selectivity of the electrodes, the chemical structure of the phenylboronic acids have to be suitably designed to bind a specific sugar. The d -fructose is known to be bound by phenylboronic acid more strongly than d -mannose and d -glucose . These results suggest that the modified electrodes may be useful for determining about a millimolar level of these sugars.…”

Section: Resultsmentioning

confidence: 84%

“…The DTBA-PBA monolayer-modified electrode was incubated in a 50 mM d -fructose solution for 20 min before measuring the CVs to complete the binding of d -fructose to the DTBA-PBA monolayer. We used here d -fructose as a prototype of sugars because d -fructose is known to be bound by phenylboronic acids rather strongly among monosaccharides . The CV recorded at pH 6 was almost the same as the CV obtained in the absence of d -fructose at the same pH, showing that the effects of sugar binding is negligible or d -fructose does not bind to the phenylboronic acid monolayer in the pH 6 solution.…”

Section: Resultsmentioning

confidence: 92%

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Phenylboronic Acid Monolayer-Modified Electrodes Sensitive to Sugars

2005

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The surface of a gold (Au) electrode was modified with 4-mercaptophenylboronic acid (MPBA) and dithiobis(4-butyrylamino-m-phenylboronic acid) (DTBA-PBA) to prepare sugar-sensitive electrodes. MPBA and DTBA-PBA formed well-packed monomolecular layers on the Au electrode through a sulfur-Au bond. The MPBA- and DTBA-PBA-modified electrodes exhibited a nearly reversible cyclic voltammogram (CV) for the Fe(CN)(6)(3-)(/4-) ion in acidic solution, while the CVs were significantly attenuated in alkaline media as a result of addition of OH(-) ion to the boron atom to generate the negatively charged surface. In other words, the negatively charged monolayers blocked the surface of the Au electrode from the access of the Fe(CN)(6)(3-)(/4-) ion. The pK(a) values of the addition equilibrium of the OH(-) ion to the MPBA and DTBA-PBA monolayers were estimated to be 9.2 +/- 0.1 and 8.0 +/- 0.2, respectively, on the basis of the pH-dependent peak current (i(p)) in the CV of the Fe(CN)(6)(3-)(/4-) ion. On the other hand, in the presence of sugars, the addition of the OH(-) ion was accelerated by forming the phenylboronate esters of sugars on the surface of the monolayers. The pK(a) values for the MPBA and DTBA-PBA monolayers were 8.3 +/- 0.1 and 7.2 +/- 0.1, respectively, in the presence of 50 mM D-fructose. The MPBA- and DTBA-PBA-modified electrodes can be used for determining sugars on the basis of the change in i(p) of the Fe(CN)(6)(3-)(/4-) ion in the presence of sugars. The calibration curves useful for determining 1-100 mM D-glucose, D-mannose, and D-fructose were obtained.

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Section: Resultssupporting

confidence: 74%

Section: Resultsmentioning

confidence: 84%

Section: Resultsmentioning

confidence: 92%

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Phenylboronic Acid Monolayer-Modified Electrodes Sensitive to Sugars

2005

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“…The photographs in Figure show the temperature effect on the release of ARS from NIPAM- co -PBA microgel at pH 10.0, where the molar ratio of PBA to ARS is 3/1. ARS is known to bind phenylboronic acid and shows different colors depending on the conditions. − Pure ARS solution is purple at pH 10.0. When it binds with boronic acid, the color turns orange.…”

Section: Resultsmentioning

confidence: 99%

Temperature-Controlled Release of Diols from N-Isopropylacrylamide-co-Acrylamidophenylboronic Acid Microgels

Zhang

2006

J. Phys. Chem. B

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N-Isopropylacrylamide-co-acrylamidophenylboronic acid (NIPAM-co-PBA) microgels were prepared by free radical polymerization in water. The release of glucose and Alizarin Red S (ARS) from the microgels as a function of temperature has been investigated by using laser light scattering (LLS) and ultrasensitive differential scanning calorimetry (US-DSC). Such microgels can bind glucose and ARS via boronic acids at a lower temperature. As the temperature increases, the microgels shrink, and the diols are released. The release could be controlled by temperature. The effect of the structure of the microgels on the release is also discussed.

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“…The possibilities further increase with the substitution pattern of the phenylboronic acid. The p K a of phenylboronic acid is 8.8, and the p K a values of substituted phenylboronic acids vary in the range 4−9 . The situation thus is genuinely complex because the various effects cannot be expected to be additive, not even approximately.…”

Section: Discussionmentioning

confidence: 99%

Coordinate Covalent C → B Bonding in Phenylborates and Latent Formation of Phenyl Anions from Phenylboronic Acid

Glaser

Knotts

2005

J. Phys. Chem. A

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The results are reported of a theoretical study of the addition of small nucleophiles Nu(-) (HO(-), F(-)) to phenylboronic acid Ph-B(OH)(2) and of the stability of the resulting complexes [Ph-B(OH)(2)Nu](-) with regard to Ph-B heterolysis [Ph-B(OH)(2)Nu](-) --> Ph(-) + B(OH)(2)Nu as well as Nu(-)/Ph(-) substitution [Ph-B(OH)(2)Nu](-) + Nu(-) --> Ph(-) + [B(OH)(2)Nu(2)](-). These reactions are of fundamental importance for the Suzuki-Miyaura cross-coupling reaction and many other processes in chemistry and biology that involve phenylboronic acids. The species were characterized by potential energy surface analysis (B3LYP/6-31+G*), examined by electronic structure analysis (B3LYP/6-311++G**), and reaction energies (CCSD/6-311++G**) and solvation energies (PCM and IPCM, B3LYP/6-311++G*) were determined. It is shown that Ph-B bonding in [Ph-B(OH)(2)Nu](-) is coordinate covalent and rather weak (<50 kcal.mol(-1)). The coordinate covalent bonding is large enough to inhibit unimolecular dissociation and bimolecular nucleophile-assisted phenyl anion liberation is slowed greatly by the negative charge on the borate's periphery. The latter is the major reason for the extraordinary differences in the kinetic stabilities of diazonium ions and borates in nucleophilic substitution reactions despite their rather similar coordinate covalent bond strengths.

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Density functional study of the lithiation of cyclic vinyl ethers in solution

Cited by 16 publications

References 12 publications

Phenylboronic Acid Monolayer-Modified Electrodes Sensitive to Sugars

Phenylboronic Acid Monolayer-Modified Electrodes Sensitive to Sugars

Temperature-Controlled Release of Diols from N-Isopropylacrylamide-co-Acrylamidophenylboronic Acid Microgels

Coordinate Covalent C → B Bonding in Phenylborates and Latent Formation of Phenyl Anions from Phenylboronic Acid

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