- Photolysis of phenacyl esters in a two-phase system
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Phenacyl esters are useful photoremovable protecting groups for carboxylic acids in organic synthesis and biochemistry. In this work, simple one-pot arrangements of the phenacyl and 2,5-dimethylphenacyl ester photolysis are proposed. The reactions were performed in both the benzene/water two-phase system and in water. Cetyltrimethylammonium bromide was found to increase substantially the efficiency of the deprotection as well as the purity of the products by lowering the interfacial tension between the phases. Utilizing water as a medium significantly reduced the necessity to use environmentally malign organic solvents. The overall yields varied from 72 to 98% depending on the reaction conditions.
- Ruzicka, Radovan,Zabadal, Miroslav,Klan, Petr
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p. 2581 - 2590
(2007/10/03)
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- 2,5-Dimethylphenacyl esters: A photoremovable protecting group for carboxylic acidsi
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Irradiation of 2,5-dimethylphenacyl (DMP) esters (la-c) in benzene or cyclohexane solutions produces the corresponding free carboxylic acids (2a-c) in high chemical yields, along with 6-methyl-l-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, 0.2, than in methanol, (f> 0.1. The photoreaction is initiated by efficient photoenolization, 01. Three transient intermediates were identified by laser flash photolysis of la, the triplet-state photoenol and the two ground-state photoenols of Z and E configuration. Release of the acids 2a-c occurs predominantly from the E isomer, which has a lifetime of about 2 ms in methanol and 0.5 s in benzene solution. The present data are essential for potential applications of the DMP moiety as a photoremovable protecting group in organic synthesis or biochemistry ( caged compounds ).
- Zabadal, Miroslav,Pelliccioli, Anna Paola,Klan, Petr,Wirz, Jakob
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p. 10329 - 10333
(2007/10/03)
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- 2,5-Dimethylphenacyl as a New Photoreleasable Protecting Group for Carboxylic Acids
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(Matrix Presented) The 2,5-dimethylphenacyl chromophore, a new photoremovable protecting group 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 of introducing a photosensitizer.
- Klan, Petr,Zabadal, Miroslav,Heger, Dominik
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p. 1569 - 1571
(2007/10/03)
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