The Coupling of Diazonium Salts with Aliphatic Carbon Atoms

Parmerter, Stanley M.

doi:10.1002/0471264180.or010.01

Cited by 3 publications

(3 citation statements)

References 354 publications

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“…Two pathways were considered for the E → Z isomerization process in the switches . A direct isomerization by rotation about the CN double bond was quickly discounted, since the activation free energies for this process in all systems were 35–45 kcal/mol above the corresponding measured energy of the systems.…”

Section: Resultsmentioning

confidence: 99%

Building Strain with Large Macrocycles and Using It To Tune the Thermal Half-Lives of Hydrazone Photochromes

Qian

Shao

et al. 2018

J. Am. Chem. Soc.

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Strain has been used as a tool to modulate the reactivity (e.g., mechanochemistry) and thermal isomerization kinetics of photochromic compounds. Macrocyclization is used to build-up strain in such systems, and in general the reactivity and rates increase with the decrease in macrocycle size. To ascertain the effect of strain on recently reported bistable hydrazone photoswitches, we incorporated them into macrocycles having varying aliphatic linker lengths (C3-C7), and studied their switching behavior, and effect of macrocycle size on the thermal isomerization rate. Surprisingly, while the systems with C3-C5 linkers behave as expected (i.e., the rate is faster with smaller linkers), the isomerization rate in the systems with larger aliphatic linkers (C6-C8) is enhanced up to 4 orders of magnitude. NMR spectroscopy, X-ray crystallography and DFT calculations were used to elucidate this unexpected behavior, which on the basis of our analyses results from the buildup of Pitzer (torsional), Prelog (transannular) and Baeyer (large angle) strain in the longer linkers.

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Section: Resultsmentioning

confidence: 99%

Building Strain with Large Macrocycles and Using It To Tune the Thermal Half-Lives of Hydrazone Photochromes

Qian

Shao

et al. 2018

J. Am. Chem. Soc.

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“…One important facet of hydrazone chemistry that has not been exploited thus far is the fact that upon appropriate substitution they can exist in solution as a mixture of isomers . 1,2,3-Tricarbonyl-2-arylhydrazones (TCAHs) for example can be present in solution as a pair of intramolecularly H-bonded isomers (Scheme ) . This H-bond causes a diagnostic low-field 1 H NMR signal for the NH proton whose chemical shift depends on the type of carbonyl group to which it is attached.…”

Section: Introductionmentioning

confidence: 99%

Isomerization Mechanism in Hydrazone-Based Rotary Switches: Lateral Shift, Rotation, or Tautomerization?

et al. 2011

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All reagents and starting materials were purchased from Acros and used without further purification. Thin layer chromatography (TLC) was performed on silica gel 60 F254 (E. Merck). Column chromatography was performed on silica gel (Silicycle, 230-400 mesh). The melting point was recorded on an Electrothermal 9100 instrument in open capillary tubes and is uncorrected. Deuterated solvents (Cambridge Isotope Laboratories and Acros) for NMR spectroscopic analyses were used as received. NMR spectra were recorded on a Varian Unity Plus 500 MHz spectrometer, with working frequency of 499.87 MHz for 1 H nuclei, and 125.7 MHz for 13 C nuclei, respectively. Chemical shifts are quoted in ppm relative to tetramethylsilane, using the residual solvent peak as a reference standard. High-resolution mass spectra were measured on a Micromass Q-Tof Ultima capable of running HR-ESI MS. UV-Vis spectra was recorded on a Shimadzu UV spectrophotometer (UV-1800). Infrared spectra were obtained using a Shimadzu IRAffinity-1 spectrometer equipped with a ZnSe Single reflection ATR. UV/Vis Titrations: Trifluoroacetic acid (CF 3 CO 2 H or TFA, Merck Uvasol, 99.5%, for spectroscopy) and triethylamine (NEt 3 , SDS, 99.3%, synthesis grade) were purchased from commercial sources and used without further purification. All analyses were carried out with spectroscopic grade acetonitrile CH 3 CN (Acros Organics, 99+% for spectroscopy), which was used as received. All solutions were protected from daylight to avoid any potential photochemical degradation. All stock solutions were prepared using an AG 245 Mettler Toledo analytical balance (precision 0.01 mg). The concentrations of the stock solutions of the targeted compounds were calculated by quantitative dissolution

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“…1,2,3-Tricarbonyl-2-arylhydrazones exist in solution as a pair of intramolecularly H-bonded hydrazone isomers , that can equilibrate in the presence of catalytic amounts of acid or base . This process results in the exchange of the relative positions of the substituents around the CN bond, i.e., E / Z isomerization.…”

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confidence: 99%

A pH Activated Configurational Rotary Switch: Controlling the E/Z Isomerization in Hydrazones

2009

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The replacement of one of the carbonyl groups in a 1,2,3-triketone-2-naphthylhydrazone with a pyridine ring yields an original molecular switch that can be switched fully, effectively, and reversibly between the E and Z configurations. This hydrazone-based, pH-controlled, molecular switch is the first example of a chemically controlled configurational rotary switch. The bistable switch exists primarily (97%) as the E configuration in solution and can be converted quantitatively to the Z-H(+) configuration upon treatment with trifluoroacetic acid. When Z-H(+) is passed over a plug of K(2)CO(3), the "metastable" Z configuration is observed using (1)H NMR spectroscopy, which thermally equilibrates to give back the E configuration. The rate of this process is dependent on the polarity of the solvent, indicating that the E/Z isomerization takes place via a rotation around the hydrazone C=N bond.

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The Coupling of Diazonium Salts with Aliphatic Carbon Atoms

Cited by 3 publications

References 354 publications

Building Strain with Large Macrocycles and Using It To Tune the Thermal Half-Lives of Hydrazone Photochromes

Building Strain with Large Macrocycles and Using It To Tune the Thermal Half-Lives of Hydrazone Photochromes

Isomerization Mechanism in Hydrazone-Based Rotary Switches: Lateral Shift, Rotation, or Tautomerization?

A pH Activated Configurational Rotary Switch: Controlling the E/Z Isomerization in Hydrazones

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