66521-22-0Relevant articles and documents
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Bergmark
, p. 61 (1978)
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2,5-Dimethylphenacyl esters: A photoremovable protecting group for carboxylic acidsi
Zabadal, Miroslav,Pelliccioli, Anna Paola,Klan, Petr,Wirz, Jakob
, p. 10329 - 10333 (2007/10/03)
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 ).
Photoenolization with α-Chloro Substituents
Bergmark, William R.,Barnes, Curtis,Clark, Jeffrey,Paparian, Seth,Marynowski, Susan
, p. 5612 - 5615 (2007/10/02)
Irradiation of a methanol solution of 2,5-dimethyl-α-chloropropiophenone (1a) produces 2,6-dimethyl-1-indanone (2a), 2-(methoxymethyl)-5-methylpropiophenone (3a), 2,5-dimethylpropiophenone (4a), and methyl 2-(2,5-dimethylphenyl)propionate (5a).It is proposed that the first two products arise from hydrogen abstraction followed by chlorine loss, the latter two from initial loss of chlorine.Making the chlorine-bearing carbon primary suppresses the formation of the latter two products, while maintaining the carbonyl nearly planar with the ring suppresses all product formation.Other examples are presented.
