Temperature Dependent Photochemical Cleavage of 2,5-Dimethylphenacyl Esters
| Autoři | |
|---|---|
| Rok publikování | 2003 |
| Druh | Článek v odborném periodiku |
| Časopis / Zdroj | Molecular Diversity |
| Fakulta / Pracoviště MU | |
| Citace | |
| Obor | Organická chemie |
| Klíčová slova | photochemistry; microwave; protecting groups |
| Popis | 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 oC 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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