Chemistry and kinetics of singlet pentafluorophenylnitrene

Synthesis of Photoactive α‐Mannosides and Mannosyl Peptides and Their Evaluation for Lectin Labeling

“…Chemical shifts are relative to TMS or the solvent peaks of CDCl 3 (δ =7. 24 For assignment of the NMR spectroscopic data 18 and 19 were numbered according to the following drawing:…”

“…[23] When polyfluorinated aryl azides such as pentafluorophenyl azides are used as photoactive reagents, irradiation leads to a stabilized singlet nitrene, which is less prone to undesired ring expansion, and is more readily trapped by nucleophiles, such as amines or alcohols and even inactivated alkanes, to form stable covalent adducts. [21,24] Thus, we synthesized an aryl azide from pentafluorobenzaldehyde, which was reacted with sodium azide in acetone-water to form p-azidobenzaldehyde 8 after regioselective nucleophilic aromatic substitution in an improved yield as compared to the literature [21] (Scheme 2). Chemoselective reduction of the aldehyde group in 8 was then accomplished with the dimethylamineborane complex in acetic acid [25] to provide the literatureknown benzyl alcohol 9 [21] in a yield of 89 % after chromatographic purification.…”

N,N-Dialkyl-N '-(2-pyridyl)formamidines and N-(3,5-dichloro-2-pyridyl)formamide. Reactions of tetrazolopyridines with nucleophiles, part 1

“…Amidine formation has also been observed in photolyses of pentafluorophenyl azide (up to 50 %) 8 and o-azidobenzonitrile (10 %) 9 in diethylamine. Thus, this type of reaction always involves electron deficient aryl-or heteroaryl azides and/or nitrenes.…”

Photochemically Initiated Single Polymer Immobilization

“…[34,35] The pathway for the adduct formation is therefore favored and insertion reaction yields are greatly enhanced. [36][37][38] Fluorinated phenylazides have gained increasing popularity in photoaffinity labeling, a technique in which a natural ligand modified with a photosensitive moiety is used to probe the binding site structure of the biological receptor. [39,40] We began applying perfluorophenylazides (PFPAs) in surface modifications and have since demonstrated that these compounds are highly efficient for the covalent immobilization of a variety of polymers.…”