Isocyanates Bloques: Etude Cinetique Et Thermodynamique

Deaguirre, I.; Collot, J.

doi:10.1002/bscb.19890980103

Cited by 21 publications

(8 citation statements)

References 7 publications

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“…For the oxalate reagents, we chose three available 2,2,2‐trifluoroethyl derivatives for testing: ethyl (2,2,2‐trifluoroethyl) oxalate ( 1c ), methyl (2,2,2‐trifluoroethyl) oxalate ( 1d ), and bis(2,2,2‐trifluoroethyl) oxalate ( 1e ), with 1b as a reference (Figure 3). The effectiveness of the aminolysis increases with a decrease of the p K a value of the alcohol leaving group (the p K a values for ethanol, methanol, and 2,2,2‐trifluoroethanol are 16, 15.5, and 12.5, respectively) 36–38. The reactivity of these reagents, therefore, should increase from 1b to 1e .…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Cytotoxicity of a Diazirine‐Based Photopsammaplin

et al. 2014

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The first photoreactive derivative of the cytotoxic marine natural product psammaplin A (1) has been synthesized by appending 1‐azi‐2,2,2‐trifluoroethyl moieties at both benzene rings. Photopsammaplin 8 exhibited anticancer activity in vitro with a geomean IC50 value of 1.4 μM in a panel of 42 human cancer cell lines. Particularly sensitive cell lines were found among bladder, lung, mammary, and prostate cancer as well as melanoma (MEXF 276), with IC50 values ≤ 0.6 μM. In a COMPARE analysis, diazirine‐functionalized photopsammaplin exhibited a very similar cytotoxicity profile to that of the natural product 1. Furthermore, photopsammaplin 8 was found to be a potent HDAC inhibitor (IC50 35 nM) and can be considered as a suitable candidate for photoaffinity labeling, which may assist in the identification of new targets of psammaplin A. Irradiation experiments with a model diazirine‐functionalized α‐hydroxy iminoester in dichloromethane in the presence or absence of acetic acid and methanol revealed the stability of the oxime unit and confirmed that reactions took place solely at the carbene center. The isolation of triplet and singlet photoproducts is consistent with DFT calculations [B3LYP 6‐311G (2d,2p)] showing that, in polar solvents, the triplet‐singlet gap is very small.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Cytotoxicity of a Diazirine‐Based Photopsammaplin

et al. 2014

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“…For instance, phenols, oximes, and pyrazoles are well known to separate from the isocyanate group and promote a fast urethane reaction under relatively low temperature conditions [29][30][31][32]. Imidazole-based derivatives are also widely used as blocking agents for coatings because of their heterocyclic structures [33][34][35].…”

Section: Introductionmentioning

confidence: 99%

“…Various BIs with pyrazole-based blocking agents have been utilized in automotive clearcoats [33,34,36,37], since they undergo less yellowing and do not release toxic hazards during thermal curing process. By varying the substituents connected to the pyrazole ring, the deblocking temperature by pyrazole derivatives can be adjusted from approximately 85 to 200 • C [3,27].…”

Section: Introductionmentioning

confidence: 99%

Effect of Urethane Crosslinking by Blocked Isocyanates with Pyrazole-Based Blocking Agents on Rheological and Mechanical Performance of Clearcoats

et al. 2020

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A novel blocked isocyanate crosslinker was synthesized, and its applicability was investigated for the low-temperature curing of automotive clearcoats. Various pyrazole derivatives were prepared as blocking agents in isocyanate crosslinkers, which strongly affect the deblocking and curing properties of the urethane-bonded coating systems. The thermal curing properties of clearcoat samples containing a pyrazole-based blocked isocyanate crosslinker and polyol resin were characterized under two different temperature conditions (120 and 150 °C). The decrease in the amount of hydroxyl groups in the polyol before and after curing was expressed by the change in OH stretching frequency in the Fourier transform infrared (FT-IR) spectra. The real-time rheological storage moduli of the bulk clearcoat mixtures were measured via a rotational rheometer to determine the effect of pyrazole-based blocking agents on the curing dynamics. In addition, a rigid-body pendulum tester (RPT) was employed to investigate the curing behavior in the thin film form. The nano-indentation and the nano-scratch tests were conducted to examine the surface hardness and scratch resistance characteristics of the cured clearcoat films. The results show that a low-temperature curing system of clearcoats can be realized by tuning the curing temperature and reactivity of isocyanate crosslinkers blocked with pyrazole-based substituents.

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“…Reactivity of the carbamate is related to a pK a value of the released alcohol: 29 ethyl carbamates (pK a (ethanol) z 16) poorly react with hydrazine resulting in longer time of the reaction; phenyl and p-nitrophenyl carbamates (pK a (phenol) z 10, pK a (p-nitrophenol) z 7) are very reactive substrates and can easily form symmetrical ureas with active amines during the synthesis of the carbamate, which complicates a one-pot transformation of the carbonate to 4-substituted semicarbazide.…”

Section: Introductionmentioning

confidence: 99%

Facile one-pot synthesis of 4-substituted semicarbazides

et al. 2015

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A diverse library of twenty-five 4-mono-and disubstituted semicarbazides was prepared in a one-pot twostep approach. The method includes formation of a carbamate from bis(2,2,2-trifluoroethyl)carbonate or 2,2,2-trifluoroethylchloroformate and a primary or secondary amine and subsequent interaction of the carbamate with hydrazine to result in a semicarbazide. The approach allowed to obtain 4-substituted semicarbazides on a large scale in good yield and high purity.

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Isocyanates Bloques: Etude Cinetique Et Thermodynamique

Cited by 21 publications

References 7 publications

Synthesis and Cytotoxicity of a Diazirine‐Based Photopsammaplin

Synthesis and Cytotoxicity of a Diazirine‐Based Photopsammaplin

Effect of Urethane Crosslinking by Blocked Isocyanates with Pyrazole-Based Blocking Agents on Rheological and Mechanical Performance of Clearcoats

Facile one-pot synthesis of 4-substituted semicarbazides

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