Photooxygenation of 2,4-Dimethyl-1,3-pentadiene: Solvent Dependence of the Chemical (Ene Reaction and [4 + 2] Cycloaddition) and Physical Quenching of Singlet Oxygen
✍ Scribed by Axel G. Griesbeck; Maren Fiege; Murthy S. Gudipati; Robert Wagner
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 143 KB
- Volume
- 1998
- Category
- Article
- ISSN
- 1434-193X
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✦ Synopsis
The photooxygenation of 2,4-dimethyl-1,3-pentadiene (1) path, leading to the allylic hydroperoxide 3) are explained by competition between a concerted and a perepoxide was investigated in seven polar and nonpolar solvents by oxygen-uptake measurements. The overall deactivation rate mechanism. In all solvents the physical quenching of singlet oxygen by 1 is at least as efficient as the chemical quenching. k o (= k r + k q ) was additionally measured in chloroform solutions by singlet-oxygen ( 1 ∆ g ) phosphorescence
The reaction of the endoperoxide 2 and 3,3,6,6-tetramethyl-1,2-dioxene 9 with carbonyl compounds in the presence of quenching which showed excellent agreement with the data from the detailed steady-state kinetics. The difference in TMSOTf resulting in the dihydrofuran 8 and the 1,2,4trioxane 10, was also studied. solvent-polarity effects on the [4 + 2] cycloaddition (major path, leading to the endoperoxide 2) and ene reaction (minor