133966-44-6Relevant articles and documents
Dye-Sensitized Photooxygenation of 2,3-Dihydrothiophenes: Formation of Stable 1,2-Dioxetanes from 4,5-Dialkyl-Substituted Derivatives
Gollnick, Klaus,Knutzen-Mies, Karen
, p. 4027 - 4031 (2007/10/02)
Singlet oxygen reacts with 4,5-dimethyl- (1a), 4-ethyl-5-methyl- (1b), and 4-isopropyl-5-methyl-2,3-dihydrothiophene (1c) to give 1,2-dioxetanes 2a-c in high yields (> 90 percent). 2a-c represents the first examples of sulfur-substituted dioxetanes that could be isolated.Less than 5 percent of allylic hydroperoxides 3a, 4a, and 3b, identified by their 1H NMR spectra, and less than 5 percent of S-oxides 5a-c were formed in competing ene reactions and sulfoxide-producing steps, respectively.Due to its decreased rigidity, dioxetane 2a is less stable than its oxygen counterpart.Increased flexibility of dioxetanes derived from dihydrothiophenes and dihydrothiopyranes, as compared to those derived from dihydrofurans and dihydropyrans, causes dioxetanes 9 and 16, obtained from 4-carbomethoxy-5-methyl-2,3-dihydrothiophene (8) and 5,6-dimethyl-3,4-dihydro-2H-thiopyran (14), to cleave into dicarbonyl compounds readily at low temperatures.Sulfur-substituted allylic hydroperoxides are also less stable than their oxygen counterparts.Formation of the expected endocyclic allylic hydroperoxides 3a, 3b, and 10 is inferred from the appearance of their H2O2 elimination products, thiophenes 7a, 7b, and 13, respectively.
