2,5-Dimethylphenacyl as a New Photoreleasable Protecting Group for Carboxylic Acids
作者:Petr Klán、Miroslav Zabadal、Dominik Heger
DOI:10.1021/ol005789x
日期:2000.6.1
The 2,5-dimethylphenacyl chromophore, a new photoremovable protectinggroup for carboxylic acids, is proposed. Direct photolysis of various 2,5-dimethylphenacyl esters in benzene or methanol at 254-366 nm leads to the formation of the corresponding carboxylic acids in almost quantitative isolated yields. The photodeprotection is based on efficient intramolecular hydrogen abstraction without the necessity
or cyclohexane solutions produces the corresponding free carboxylicacids (2a−c) in high chemical yields, along with 6-methyl-1-indanone (3). In methanol, 2-(methoxymethyl)-5-methylacetophenone (4) is formed as a coproduct. Quantum yields for the photorelease of the DMP group are higher in nonpolar solvents, φ ≈ 0.2, than in methanol, φ ≈ 0.1. The photoreaction is initiated by efficient photoenolization