Epoxide hydrolysis

Using this crude mung bean preparation, the production of (R)-p-nitrostyrene oxide was achieved in 82% ee and 83.5% yield. After recrystallization, greater than 99% ee was achieved. 

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A recent publication describes the protection of a S-keto-A" system via its eniminium salt, permitting enol acetylation of a 20-ketone, epoxidation, hydrolysis and finally removal of the A-ring protecting group. 

Alkenes are reduced by addition of H2 in the presence of a catalyst such as platinum or palladium to yield alkanes, a process called catalytic hydrogenation. Alkenes are also oxidized by reaction with a peroxyacid to give epoxides, which can be converted into lTans-l,2-diols by acid-catalyzed epoxide hydrolysis. The corresponding cis-l,2-diols can be made directly from alkenes by hydroxylation with 0s04. Alkenes can also be cleaved to produce carbonyl compounds by reaction with ozone, followed by reduction with zinc metal. 

From what alkene was the following 1,2-diol made, and what method was used, epoxide hydrolysis or Os04 ... 

The above is a typical example of a transannular hydride shift. The 1,2-diol is formed by a normal epoxide hydrolysis reaction (10-7). For a discussion of 1,3 and... 

Diols are applied on a multimilhon ton scale as antifreezing agents and polyester monomers (ethylene and propylene glycol) [58]. In addition, they are starting materials for various fine chemicals. Intimately coimected with the epoxidation-hydrolysis process, dihydroxylation of C=C double bonds constitutes a shorter and more atom-efficient route to 1,2-diols. Although considerable advancements in the field of biomimetic nonheme complexes have been achieved in recent years, still osmium complexes remain the most efficient and reliable catalysts for dihydroxylation of olefins (reviews [59]). 

Arene oxides and diol epoxides are generally unstable in aqueous, especially acidic media (103-105). and in addition, several groups have noted that DNA has a marked catalytic effect upon diol epoxide hydrolysis (106.107). However, in cells there appears to be sites, probably lipid in nature, in which these compounds can have much longer half-lives. 

N. S. Finney, Enantioselective Epoxide Hydrolysis Catalysis Involving Microbes, Mammals and Metals , Chem. Biol. 1998, 5(4), R73 - R79. 

G. Bellucci, C. Chiappe, A. Cordoni, F. Marioni, The Rabbit Liver Microsomal Biotransformation of 1,1-Dialkylethylenes Enantioface Selection of Epoxidation and Enantioselectivity of Epoxide Hydrolysis , Chirality 1994, 6, 207 - 212. 

In conclusion, the chiral salen Co(III) complexes immobilized on Si-MCM-41 colud be synthesized by multi-grafting method. The asymmetric synthesis of diols from terminal olefins was applied with success using a hybrid catalyst of Ti-MCM-41/chiral Co(III) salen complexes. The olefins are readily oxidized to racemic epoxides over Ti-MCM-41 in the presence of oxidants such as TBHP, and then these synthesized diols are generated sequentially by epoxide hydrolysis on the salen Co(lll) complexes. This catalytic system may provide a direct approach to the synthesis of enantioselective diols from olefins. 

Since the hydroxyl groups in the diol product have a trans relationship, the product can only be formed by epoxide hydrolysis. (Treatment of the alkene with OsC>4 yields a product in which the two -OH groups have a cis relationship.)... 

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