Photochemistry of fluorophenyl azides in diethylamine. Nitrene reaction versus ring expansion

Leyva, Elisa; Sagredo, Ruben

doi:10.1016/s0040-4020(98)00403-7

Cited by 41 publications

(27 citation statements)

References 27 publications

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“…The hydrogel produced in water exhibits a lower crosslink density and consequently a much higher molecular weight between crosslinks than the other hydrogels. This outcome can be attributed to the photochemistry of phenyl azides, which has been studied extensively by a number of workers 20–27…”

Section: Resultsmentioning

confidence: 99%

A photochemical method for immobilization of azidated dextran onto aminated poly(ethylene terephthalate) surfaces

Bhat

James

Jayakrishnan

2007

Polymer International

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BACKGROUND: Dextran, a bacterial polysaccharide, has been reported to be as good as poly(ethylene glycol) in its protein-rejecting and cell-repelling abilities. In addition, the multivalent nature of dextran is advantageous for surface grafting of biologically active molecules. We report here a method to photochemically bind dextran hydrogel films to aminated poly(ethylene terephthalate) (PET) surfaces in aqueous media using a heterobifunctional crosslinker, 4-azidobenzoic acid. In order to achieve this, dextran was first functionalized with the crosslinker using carbodiimide chemistry followed by photo-crosslinking and immobilization onto the nucleophile-rich aminated PET surfaces. RESULTS:The presence of the immobilized dextran on PET was verified by attenuated total-reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and contact angle measurements. The grafted surface was highly hydrophilic due to the heavily hydrated polysaccharide network on the surface as demonstrated by the near zero water contact angle. CONCLUSION: A photochemical method for surface immobilization of dextran onto aminated PET using aryl azide chemistry is a facile technique to generate highly hydrophilic and more hemocompatible surfaces. The aryl nitrenes generated by photolysis produce a metastable, electron-deficient intermediate, azacycloheptatetraene, which is believed to be responsible for the simultaneous crosslinking of dextran and its immobilization onto the aminated PET surface. The aryl azide chemistry reported here for dextran could be useful as a versatile technique for surface modification of other nucleophile-rich polymers to create dextran-or similar polysaccharideimmobilized surfaces.

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Section: Resultsmentioning

confidence: 99%

A photochemical method for immobilization of azidated dextran onto aminated poly(ethylene terephthalate) surfaces

Bhat

James

Jayakrishnan

2007

Polymer International

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“…Singlet phenyl nitrene 2 undergoes intersystem crossing to triplet nitrene 3 at 77 K while it undergoes ring expansion to didehydroazepine 4 at room temperature. Recently, we reported that two fluorine substituents ortho to the nitrene group retard ring expansion of this intermediate [25] and allow bimolecular capture of singlet phenyl nitrene 2. Therefore, the rate of ring expansion of an aryl azide is affected by steric and electronic effects of the substituents.…”

Section: Introductionmentioning

confidence: 99%

Photochemistry of fluorophenyl azides in aniline

Leyva

Sagredo

Moctezuma

2004

Journal of Fluorine Chemistry

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“…221 The cyclization of singlet nitrene to the unsubstituted ortho carbon only was observed also in the case of orthofl uorophenylnitrene. 222 These results 220 -222 demonstrate that steric effects play a role in determining the barrier to ring expansion.…”

Section: Photochemistry Of Simple Derivatives Of Phenyl Azidementioning

confidence: 94%