2,3-butene oxide ring opening

Long-chain derivatives of pyrazolyl pyridines coordinated to MoO(02)2 as 35 may efficiently replace the conventional Mo(CO)e in the oxidation of several double-bond typologies with TBHP, in non-polar hydrocarbon solvents . The epoxidation of cyclopentene and 2,3-dimethyl-2-butene led to the corresponding epoxides, notoriously sensitive to ring opening, in 100% and 87% yield respectively, in isoctane, with 1 hour reaction time. Recent advances in the epoxidation of a-pinene and other terpenes using the Mo-TBHP system have been reported. ... 

Whereas the hydrolysis of l-chloro-2-butene gives comparable yields of products from attack of solvent at both primary and secondary carbons, very little product from the acid-catalyzed hydrolysis of butadiene oxide 10 is formed from the attack of solvent at the primary carbon. The transition state for acid-catalyzed epoxide ring opening has a relatively reactant-like geometry, and therefore positive charge de-localization into the adjacent double bond at the transition state is expected to be less than that for allyl chloride hydrolysis. 

The HKR of epichlorhydrine (X = Cl, Scheme 141) and 4-hydroxy-l-butene oxide (X = OH, Scheme 141), the dynamic kinetic resolution of epibromhydrin and the enantioselective ring opening of epoxides by phenol were examined. In the first experiment, combination of the crude organic soluble products of the five recycle reactions and concentration led to the (5)-epichlorhydrine in 41% overall yield and > 99% ee and the (/ )-chlorodiol in 93% ee. In the second one, the sum of five experiments provided (iS)-triol in 36% overall yield and 94.4% ee while the enantioselectivity of the epoxide was only 59% ee. 

The activating effect of electron donor groups, such as methyl groups, Is also shown by the polymerization of els- and trans-2-butene oxides. Vandenberg used these monomers to offer the first proof that the ring opening reaction in cationic polymerization proceeded with clean Inversion of configuration (22). 

Frey et al. used 1,1-dimethylcyclopropane as a probe. With sMMO from M. richosporium OB3b, this substrate is oxygenated to (1-methylcyclopropyl)methanol, 3-methyl-3-buten-l-ol, and 1-methylcyclobutanol, in the relative yields shown in eq. (14) [76]. The formation of the ring-opened product suggests a mechanism involving some intermediate rather than a concerted mechanism. Formation of 1-methylcyclobutanol is probably via not a radical intermediate but a carbonium cation. A carbon radical formed by the H-abstraction is oxidized to the carbonium cation by one-electron transfer to an electron deficient active species, probably a resultant diiron(III,IV) intermediate. The... 

The oxides show catalytic activities for alkylation of phenol with methanol, butene isomerization, and carene isomerization. The alkylation activity correlates with acidity, while butene isomerization activity correlates with basicity. 3-Carene undergoes selective double bond migration to 2-carene on the binary oxide containing 90% ZnO, while menthadiene and cymene are produced by a three-membered ring opening over the catalyst containing small amounts of ZnO, acidic binary oxides. 

Others The binary oxide Z1O2 —SnOz has both acid and base sites. The maximum strength of the acid sites is observed to be Ha= —3.0 at the composition ZrOz 90%. The acid sites on oxides of other compositions are weaker than ifo=1.5. The number of base sites on the binary oxide is less than on the component oxide ZrOz- The catalytic activities for cyclopropane ring opening and 2-butanol dehydration correlate with the acidity, while those for 1-butene isomerization and diacetone alcohol decomposition correlate with basicity. 

Treatment of oxacyclopropanes with water in the presence of catalytic acid or base leads to ring opening to the corresponding vicinal diols. These reactions follow the mechanisms described in Section 9-9 The nucleophile (water or hydroxide) attacks the side opposite the oxygen in the three-membered ring, so the net result of the oxidation-hydrolysis sequence constitutes an anti dihydroxylation of an alkene. In this way, tram-2-butene gives me50-2,3-butanediol, whereas ds-2-butene furnishes the racemic mixture of the 1R, >R and 2S,3S enantiomers. 

The titanium-mediated photocatalytic oxidation of a pyridine solution was conducted by Low et al. (1991). They proposed that the reaction of OH radicals with pyridine was initiated by the addition of a OH radical forming the 3-hydro-3-hydroxypyridine radical followed by rapid addition of oxygen forming 2,3-dihydro-2-peroxy-3-hydroxypyridine radical. This was followed by the opening of the ring to give At-(formylimino)-2-butenal which decomposes to a dialdehyde and formamide. The dialdehyde is oxidized by OH radicals yielding carbon dioxide and water. Formamide is unstable in water and decomposes to ammonia and formic acid. Final products also included ammonium, carbonate, and nitrate ions. 

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