Spectroscopy endoperoxides

The endoperoxides (49) of oxazoles also undergo clean rearrangements following the path outlined in Scheme 6 <88TL1007>. The initial product is a dioxazole (50) identified at low temperature by NMR spectroscopy <90JCS(P1)1011>. Subsequent products are the imino anhydride (51) followed by... 

Peroxovanadates, O NMR spectroscopy, 186 PeroxyacetaUzation of carbonyl functions ji-hydroperoxyalcohols, 273-7, 278 strained endoperoxide systems, 277-85... 

The mechanism of photooxygenation has been studied for a range of substituted imidazoles 45 (Scheme 14). It proceeds via the endoperoxide 46, which has been detected by H-NMR spectroscopy in certain instances, giving 47 for triarylimidazoles, 48 reversibly at low temperatures for R = alkyl, R = R = and a variety of different products for other... 

In 1995, the RB-sensitized photooxygenation of 6,6-diethoxyfulvene (103) in acetone-d6 at — 78 °C afforded diethoxyfulvene endoperoxide (104) as a primary product (Scheme 11.23) [117]. On the basis of 1H NMR spectroscopy at —50 °C, the initial endoperoxide 104 was assigned, but the dioxetane, 105, was not observed. Further photooxygenation resulted in the formation of bisperoxides syn-106 and the anti-106 in a 9 1 ratio. Peroxides 104 and 106 were not stable and not isolated. Above — 30 °C, endoperoxide 104 released oxygen and gave back fulvene 103, while the bisperoxides 106 decomposed to cis-butenedial, diethylcarbonate, and carbon monoxide. 

Alkene Oxidation Reactions. The reaction of triethylsilane with ozone and use of the intermediate triethylsilyl hydrotrioxide in oxidation reactions have been described. Initial oxidation reactions reported included the formation of the 9,10-endoperoxide from 9,10-dimethylanthracene (eq 1), and an allyUc hydroperoxide from 2,3-dimethyl-2-butene (eq 2). Researchers also observed a near-IR emission from triethylsilyl hydrotrioxide as it decomposed at —60°C, consistent with generation of singlet oxygen. Other workers have characterized triethylsilyl hydrotrioxide by NMR spectroscopy and and measured the kinetics of its decomposition in deuterated acetone. ... 

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