Monocyclic peroxides

Saturated aldehyde (XXII) and a,3 - unsaturated aldehyde (XXI) groups are produced upon decomposition of the monocyclic-peroxide structures and are depicted In the Ir spectra by bands at 1725 and 1700 cm, respectively. Structures (XVa), (XVc), and (XVIa) lead to the saturated and unsaturated pairs, while (XVb) and (XVIb) would yield only saturated aldehydes. In the temperature range of 60-120 0, unsaturated and saturated aldehydes detected are of comparable Intensity, consistent with formation of (XVa), (XVc), and (XVIa). The formation of (XVb) and (XVIb)... 

Perhaps the best documented case of peroxy radical cyclization was the report (5) that a-famesene undergoes radical autoxi--dation to yield the completely characterized monocyclic peroxide, Autoxidative peroxy radical cyclization has precedent, then, but this autoxidation format is cumbersome for a systematic study. 

We developed a method for the study of peroxy radical cycli-zation based on the generation of peroxy radicals from unsaturated hydroperoxides (jS, T) Thus, treatment of the hydroperoxide with free radical initiators such as DBPO ( ) led to the formation of monocyclic peroxides that could be isolated by liquid chromatography and characterized by standard techniques. 

Since the earlier reviewers, and Mallory and Wood, and, for the earlier literature, Hammick el al. have summarized the history of the structure problem fairly fully, and since it cannot in any case be treated properly in isolation from that of the monocyclic furoxans, we shall present only a brief outline here. The earliest formulas to be suggested (3 and 4), in connection with 1,2-naphthofuroxan, discovered by Koreff and von Ilinski in 1886, were open to the objections that the first is a peroxide structure, whereas the benzofuroxans... 

Very little is known concerning the simple, monocyclic 3-hydroxy-furans (cf. reference 15). Both the oxo and hydroxy forms of the substituted 3-hydroxyfurans 26 and 27 (R = H, CcHn) have been isolated/ but the individual tautomers slowly undergo interconversion. The enol forms give a positive reaction with ferric chloride, react rapidly with bromine, and form a peroxide with oxygen. From chemical evidence, the benzo derivatives of 3-hydroxyfuran, 28 and 29, appear to exist predominantly in the oxo form, and this is further supported by ultraviolet spectral data. Stefanye and Howard- ... 

Relatively little systematic work has been carried out on the thermal behaviour of the bicyclic peroxides compared to monocyclic systems 63). From the few results obtained to date, oxygen diradicals appear to be reasonable intermediates to account for the observed products (Eq. 51). 

August et al. (1998) conducted kinetic studies for the reaction of benzene (0.2 mM) and other monocyclic aromatics with Fenton s reagent (8 mM hydrogen peroxide [Fe ] = 0.1 mM) at 25 °C. They reported a reaction rate constant of 0.0530/min. 

Chemical/Physical. In an aqueous solution, nitrobenzene (100 pM) reacted with Fenton s reagent (35 pM). After 15 min, 2-, 3-, and 4-nitrophenol were identified as products. After 6 h, about 50% of the nitrobenzene was destroyed. The pH of the solution decreased due to the formation of nitric acid (Lipczynska-Kochany, 1991). August et al. (1998) conducted kinetic studies for the reaction of nitrobenzene (0.2 mM) and other monocyclic aromatics with Fenton s reagent (8 mM hydrogen peroxide [Fe ] = 0.1 mM) at 25 °C. They reported a reaction rate constant of 0.0260/min. 

The sultam, 32, has been prepared from the monocyclic precursor 98 followed by treatment with basic H2S. Oxidative disulfide formation with either molecular oxygen or hydrogen peroxide then yields the product (Equation 20) <2005HCA1208>. 

The monocyclic saturated peroxides (144 R = H, Me) have been prepared by the treatment of the hydroperoxides (143) with LTA (81S633). 

---