Abstract
The study of the temperature-sensitive photochemical release of a carboxylic acid from 2,5-dimethylphenacyl ester is reported. Quantum yields of the benzoate ester degradation in benzene increased from 0.22 at room temperature to 0.28 at 50 °C whereas a more significant increase (nearly by a factor of 3) was observed in methanol and ethanol, reaching a high reaction efficiency (0.25) typically found in non-polar solvents. The reaction proceeds predominantly via the triplet pathway and the E-photoenol in the whole temperature range in methanol solution. A higher quantum efficiency in heated methanol is explained by enhancing the E-photoenol population. This picture was partially confirmed by the quantum chemical calculations. The 2,5-dimethylphenacyl chromophore is proposed as an efficient photoremovable protecting group for carboxylic acids in solutions under conventional or microwave-assisted heating for applications in organic synthesis, such as the solid-phase synthesis.
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Literík, J., Relich, S., Kulhánek, P. et al. Temperature dependent photochemical cleavage of 2,5-dimethylphenacyl esters. Mol Divers 7, 265–271 (2003). https://doi.org/10.1023/B:MODI.0000006862.98763.dd
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DOI: https://doi.org/10.1023/B:MODI.0000006862.98763.dd