Ring-opening oxidation

Other reactions include reductive ring opening, oxidative ring opening, ihermal and phnlnchemical reactions, and polymerization. 

N-Methylindole acts like an enamine with sulfonyl azides and gives a diazoimino compound.443-445 So does dihydropyridine but only in the presence of 5% lithium hydroxide (Scheme 147).242 A triazole is postulated to be formed from the triazoline followed by a ring opening oxidation of diazoamino compounds to triazoles has been known to proceed via a diazoimino compound in equilibrium with the triazole (Scheme 1 19).285-3"-400... 

Figure 9-26. The various types of oxidation reaction catalysed by metalloenzymes. The conversion of a phenol to a 1,2-dihydroxybenzene and the ring opening oxidation both involve oxygen atom transfer to the substrate, whilst the oxidation of a 1,2-diol to a 1,2-quinone is of the type discussed earlier in this chapter.

Figure 9-28. The ring-opening oxidation of catechol by dioxygen in the presence of copper salts. The first step presumably involves an electron transfer type of process to generate the quinone, followed by the oxygen atom transfer in the second step.

In 1,2,4-triazines it is essential that the 5-position is blocked (cf. pyrimidines without 4- or 6-substituents) to prevent nucleophilic ring opening, oxidation, and ring contractions from competing with N-oxidation (72LA111 86H951). Products include l,2,4-triazin-5-ones and -5,6-diones (72LA111). Whereas... 

The ring-opening oxidation with nitric acid of 3,7i-dibromocamphor (246) has been re-examined by Brienne and Jacques, who have shown that treatment of the r-bromocamphoric acid (247 R = H) thus obtained with one equivalent of alkali gives the unusual trans-fused y-lactone [(248 R = H), the trans-n-cam-phanic acid of the 19th century]. The structure already derives from the fact that... 

The known transformations of naphtho[l,8-Z)c]thiete (34) and its S-oxides 35,36 in the majority of instances consist of hetero ring opening due to irradiation, heating or to the action of chemical reagents. However, two types of reactions are known that are directed to the sulfur atom and do not cause ring opening oxidation to S- oxides, and S-alkylation giving sulfonium salts. 

Pterin 8-oxides, - 24,437 Purine ring opening, oxidative 24, 241 Purines... 

Previously we pointed out that the oxidation of alkenes in water allows one-pot multi-step reactions to be carried out involving tandem epoxidation and ring-opening reactions. Further examples are the synthesis of optically active trifluorolactic acid by aqueous nitric acid ring-opening oxidation of (-)-l,2-epoxy-3,3,3-trifluoropropane [19] in the presence of a catalytic amount of copper metal ... 

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