Photochemistry of 2-nitrobenzylidene acetals
Language English Country United States Media print
Document type Journal Article
PubMed
19824651
DOI
10.1021/jo901756r
Knihovny.cz E-resources
- MeSH
- Acetals chemistry MeSH
- Benzylidene Compounds chemistry MeSH
- Models, Chemical MeSH
- Photochemistry * MeSH
- Photolysis MeSH
- Quantum Theory MeSH
- Computer Simulation MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- 2-nitrobenzylidene acetal MeSH Browser
- Acetals MeSH
- Benzylidene Compounds MeSH
Photolysis of dihydroxy compounds (diols) protected as 2-nitrobenzylidene acetals (ONBA) and subsequent acid- or base-catalyzed hydrolysis of the 2-nitrosobenzoic acid ester intermediates result in an efficient and high-yielding release of the substrates. We investigated the scope and limitations of ONBA photochemistry and expanded upon earlier described two-step procedures to show that the protected diols of many structural varieties can also be liberated in a one-pot procedure. In view of the fact that the acetals of nonsymmetrically substituted diols are converted into one of the corresponding 2-nitrosobenzoic acid ester isomers with moderate to high regioselectivity, the mechanism of their formation was studied using various experimental techniques. The experimental data were found to be in agreement with DFT-based quantum chemical calculations that showed the preferential cleavage occurs on the acetal C-O bond in the vicinity of more electron-withdrawing (or less electron-donating) groups. The study also revealed considerable complexity in the cleavage mechanism and that the structural variations in the substrate can significantly alter the reaction pathway. This deprotection strategy was found to be also applicable for 2-thioethanol when released from the corresponding monothioacetal in the presence of a reducing agent, such as ascorbic acid.
References provided by Crossref.org
Photoremovable protecting groups in chemistry and biology: reaction mechanisms and efficacy