o-Nitrophenylethylene glycol as photoremovable protective group for aldehydes and ketones: syntheses, scope, and limitations

Abstract

The preparation of o-nitrophenylethylene glycol is described along with its application as a photolabile protective group for aldehydes and ketones. Formation of the acetals and ketals is achieved in good to high yields in the usual manner and deprotection is carried out in fair to high yield, by photolysis at 350 nm in an inert solvent such as benzene. Because of the particular nature of the present protective group, its stability to basic and acidic conditions has been examined and is reported to complete the scope and limitations aspect. From a mechanistic point of view, the isolation and characterization of o-nitroso-α-hydroxyacetophenone as the spent reagent demonstrates a mechanistic link with the known o-nitrobenzaldehyde to o-nitrosobenzoic acid photorearrangement.

A caged progesterone analog alters intracellular Ca2+ and flagellar bending in human sperm

“…Progesterone (1.57 g, 5 mmol), 2-nitrophenylethanediol (3.66 g, 20 mmol), and p-toluenesulfonic acid (75 mg) were dissolved in benzene (70 ml) and heated under reflux through anhydrous MgSO 4 for 16 h (Gravel et al 1983). The solution was washed with 10% NaHCO 3 aq and saturated NaCl aq, and the organic layer was dried over anhydrous MgSO 4 and evaporated to give the mixture of isomers of caged progesterone (3.1 g).…”

Phototriggered Acid Proliferation to Enhance Photosensitivity of Chemically Amplified Photoresists

“…As shown in Figure 1, the absorption band at the wavelength maximum (k max = 262 nm) of 1 decreased, and new bands appeared at 290 nm and 314 nm due to the formation of o-nitroso-a-hydroxyacetophenone which has k max at 286 nm and 310 nm in EtOH. [22] An isosbectic point exists in the early stage of the photolysis, indicating that the photoreaction of 1 proceeds through the A-to-B type conversion, supporting that the photoinduced deprotection of 1 occurs to generate the b-tosyloxy ketone. After irradiation of an exposure dose of 1.92 J/cm 2 absorption spectra deviated gradually from the isosbectic point.…”

“…[10,18] The acidolysis of the ethylene ketal gives the corresponding b-tosyloxy ketone which is readily subjected to the belimination to release TsOH due to the electron-withdrawing carbonyl group, leading to the autocatalytic decomposition. On the other hand, it was reported that onitrophenylethylene acetals and ketals are photolyzed in aprotic solvents to form aldehydes or ketones and onitroso-a-hydroxyacetophenone as seen in Scheme 1 [22] These facts had led us to an idea to protect b-tosyloxy ketone with o-nitrophenylethylene glycol to form the photolabile o-nitrophenylethylene ketal of 1-phenyl-3-tosyloxy-1-propanone (1). The ketal is expected to generate TsOH after the photochemical deprotection and the subsequent thermal b-elimination to initiate the proliferation of TsOH according to Scheme 2.…”

Media with photoinduced irreversible fluorescence

“…Efforts toward developing photolabile protecting groups for carbonyl compounds date back three decades, and progress has been made since [50][51][52][53][54][55][56][57][58][59][60][61]. Nevertheless, apparent drawbacks hinder the use of those approaches in organic synthesis and biomedical research.…”